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Table Contents

Triumph makes a mechanic out of a man

The Bonnie Ref

A Hyperlink Junkie's Illustrated Field Guide
to the 1969 Triumph Bonneville

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Manual/Tech Bulletin icon Manual/Tech Bulletin   Parts Illustration icon Parts Illustration   Special Tool icon Special Tool   Photograph icon Photo   World Wide Web icon WWW Link   YouTube Video icon Video

Icon for left-handed thread LH Thread   Tips!Tips   Traps!Traps   CompatibilityCompatibility

Triumph Documentation

Workshop Manuals Manual icon

1969 650 General Data Manual icon

Triumph Service Bulletins Manual icon

Parts Books & Manuals DownloadsManual icon

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Parts Lists & Special Tools

Converting Part Numbers from Alpha-Numeric to Numeric

Hyperlinked Parts Lists & Illustrations Parts icon

Torque Settings Parts icon

Special Tools Tool icon

Other Lists & Charts Parts icon

Online Parts Sources

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Table Contents

Online Parts Suppliers Parts icon

See also: Classic British MC Links -> Parts ->British

North America

United Kingdom

Other Online Resources

Hermit's Classic British MC Links - All links No ads

Links for parts and service providers, accessories, books, clubs, history, tools, technical info, and more.

Online Forums

Additional Info Manual icon

British Fastener Specifications Parts icon

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General Shop Info


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Alpha-Numeric Part Number Conversion

Alpha-Numeric conversion chart

Left-Hand Threads

Icon for left-handed thread You've leaned on it, heated it and pounded it and that part STILL won't come out! Duh, it's a left-hand thread! Don't drive yourself nuts, consult this illustrated list of the five left-hand fasteners on a 1969 Triumph 650. Or look for the left-hand signs below in The Bonnie Ref.

Fastener Threads Used on British Motorcycles


WWW icon Baconsdozen Kevin C. Bacon's history and descriptions of Whitworth (BSW), BSF, BSC, UNC, UNF, SAE, AF, and BA. Includes Bacon's own size charts with conversions to metric and decimal inch dimensions. A must-read, top to bottom, richly informative.

WWW icon "Nuts n' bolts" A thread about nuts and bolts - how can you resist? Some interesting bits on plating, stainless, sizes, threads, and Stuart's run at BSW/BSF wrench sizes.

Common motorcycle threads chart

SAE threads



The British standard threads

Note that while American wrenches are measured across the flats (AF) of the bolt head, wrenches for the bolts in the British standard thread family are measured by the diameter of the bolt's threads.

Chart of wrench size equivalents, Whitworth-BS






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Wrench Jaw Gap Sizes

Sealants and Loctite


WWW icon Which Gasket sealer, there are so many

WWW icon TR7RVMan on sealants, and how to know if your Hylomar is out of date

WWW icon "T100R gearbox assembly sealant"

WWW icon John Healy, the only four places to use Loctite on a Triumph

WWW icon "Loctite plastic gasket"

Where to Use Loctite

Where to use Loctite thread locker on a Triumph 650 is a question that will elicit different answers depending upon who is asked.

The Loctite Gospel: According to John

According to John Healy (see link above), there are just four places to use Loctite on a Triumph 650:

  1. Mainshaft kickstarter nut - Blue (21-0594 UNF 9/16-18TPI Thin Ref.26, Fig.8, #7)
  2. Clutch nut - Blue (21-0586 UNF 9/16-18TPI Ref.1, Fig.10, #7)
  3. Rotor nut - Blue (70-3977 7/16-26TPI Ref.25, Fig.1, #7))
  4. The three flywheel bolts - Red (70-3907 Ref.6, Fig.1, #7)

The Loctite Gospel: According to Thomas

Thomas G. Gunn, Jr., in his seminal 1987 work "Overhaul Manual For 650cc Unit Construction Triumph Motorcycle Engines since 1963", suggests using Loctite in six places:

  1. The 6 countersunk screws (for 1969 models: 57-1040 Ref.8 Fig.10 #7) securing the inner/outer clutch center plates.
  2. The counter sprocket (for 1969 models: 57-1918/57-1916/57-1917/57-1919/57-1952/57-1953 Ref.12 Fig.8 #7). "The sprockets are now being "Loctited" to the 4th gear at the factory".
  3. Screw plug for the sludge trap (70-3905 Ref.4 Fig.1 #7) "The sludge trap plugs are now being "Loctited" at the factory".
  4. The 3 flywheel bolts (70-3907 Ref.6 Fig.1 #7).
  5. The nut (70-1310 BSC 5/16-26TPI Ref.15 Fig.23 #7) that secures the oil pipes and junction block to the crankcase.
  6. The 3 stator studs (21-1866/21-1867 Ref.16/17 Fig.11 #7).

It's interesting to note that out of John Healy's four places to use Loctite and Thomas G. Gunn Jr.'s six places, the only concurrence between the two lists is the crankcase bolts.

Other disciples have suggested using Loctite on crankcase studs, although in that application it's used more as a sealant than as a thread locker. In addition, amateur Loctite enthusiasts (now who said that?) have devised many other ingenious applications as well.

Sealants: Where? and What Kind?

The following chart, an interpretation/extrapolation of the links above, summarizes opinions about which sealant and which thread lockers to use, and where. Green dot items are commonly recommended, while yellow dots indicate that extra caution is required. Red dotted scenarios may best be avoided altogether. Rationale for the classifications should be apparent from the product descriptions that follow.

Chart showing where to use sealants and what kind to use

Loctite & Sealant Product Characteristics

A brief outline of some of the characteristics of a few popular sealant and Loctite products.

Loctite Blue

Loctite 518


Three Bond 1130



Applying Heat


WWW icon "Heating Engine Cases & Other Parts"

Oven, barbecue, hot tub - your choice.

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Routine Maintenance & Lubrication


Manual icon Workshop Manual (1969 650cc Twins) Section A: Lubrication Table of Contents

Manual icon Workshop Manual (1969 650cc Twins) Section A1: Routine Maintenance

Manual icon Workshop Manual (1969 650cc Twins) Section A2: Recommended Lubricants

Trap!Oil products have changed a great deal since the '60s. The WS Manual lubricant recommendations are outdated and obsolete. For modern oil recommendations see individual sections below.

Engine Lubrication


Manual icon Workshop Manual (1969 650cc Twins) Section A3: Engine Lubrication

Icon for manual Percentage of Zinc Content for Popular Oils

WWW icon Comments & recommendations (UK & US) on crankcase oil/ZDDP (zinc) and gearbox oil/yellow metals

WWW icon Very informative synthetic oil thread

WWW icon 540ratblog "Motor Oil Engineering Test Data"

WWW icon "Crankcase vent tube discharge question" TR7RVMan elucidates upon Triumph crankcase venting

WWW icon "Tech 101: Zinc in oil and its effects on older engines"

Diagram of Triumph Unit 650 Engine Lubrication System

Illustration of Unit Construction Triumph 650 lubrification system

Selecting an Engine Oil

According to the article "Tech 101: Zinc in oil and its effects on older engines", modern oil manufacturers have reduced the amount of 'zinc' (actually ZDDP [zinc dialkyldithiophosphate] or ZDTP [zinc di-thiophosphate]) in their products for various reasons, including prolongation of the life of catalytic converters. When used in older (classic) car and motorcycle engines, the low-zinc products fail to provide sufficient protection against start-up engine wear.

Using a list giving the zinc content for for popular oils, I selected Shell Rotella 15W-40.

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Changing Engine Oil


Icon for manual Workshop Manual (1969 650cc Twins) Section A4: Changing the Engine Oil & Cleaning the Filters

Triumph specified an engine oil change interval of 1,500 miles. Of course the only oil filtering back in the day was the wire screens in the oil tank and the crankcase.

Even after I installed an external oil filter (see "Using an Oil Filter" just below), I continued changing engine oil (and filter) at 1,000 mile intervals. And to simplify things I change crankcase oil and primary chaincase oil at the same time. So far, oil changes are cheaper than engine rebuilds!


Drain bolts

Some point out the difficulty in cleaning thoroughly around the crankcase oil drain plug due to its proximity to the crankcase joint and the angle at which they meet. They suggest that removing the crankcase drain bolt is a bad idea because of the attendant risk of contaminating engine oil with dirt.

Since only a small amount of oil (less than a quarter of a cup) drains out of the crankcase anyway, I adopted the practice of removing the drain plug once a year during winter maintenance to inspect and clean the filter screen. The same goes for the filter screen in the oil tank.

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Using an External Oil Filter


WWW icon Glenn "Phrog" Davidson's Norton filter head mounting bracket design

WWW icon Complete external filter kit Will fit 650s - contact seller

Icon for manual Colorado Norton Works Oil Filter Adaptor for Norton Filter Head

Probably the single most important modification one can make to a classic British bike is to install a modern external oil filter. It has been said that doing so can quadruple the life of an engine.

The most common retro-fit oil filter system utilizes a Norton-type oil filter head, connected in the return oil line between the oil pump and the oil tank, as diagrammed below.

Illustration of Triumph oil line connections for add-on oil filter

The go-to mounting bracket design is that of Glenn Davidson (see link above). The oil filter head and Davidson-style mounting bracket are commonly mounted at the bottom of the down tube, facing the rear of the bike, but other configurations are possible, see links above.

Note that the Triumph oil tank connections and oil pipe junction block pipes are 1/4", while those of the Norton filter head are 3/8". The compromise is to use 5/16" (automatic transmission cooler) hose to make the connections between the filter head and the oil tank and oil junction block. It is a very tight fit on the filter head's 3/8" fittings, and somewhat loose on the 1/4" pipes of the oil tank and oil junction block, but once they are well-clamped the connections shouldn't leak.

Filters for use With standard Norton filter head

The following filters work satisfactorily with the Norton filter head, and others can be found on cross-reference lists online.

Colorado Norton Works Filter Adaptor

A simple double-threaded adaptor is available from Colorado Norton Works (see link above) which permits use of more widely available and potentially less expensive oil filters, such as the following:

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The Oil lines


Icon for manual Workshop Manual (1969 650cc Twins) Section A8: Removing & Replacing the Oil Pipe Junction Block

Icon for manual Workshop Manual (1969 650cc Twins) Section A9: Removing & Replacing the Rocker Oil Feed Pipe

Parts iconFig.23 Oil Tank & Oil Lines

Oil Line Connections for Stock Condition - No External Oil Filter

Traps!Incorrect installation of oil lines will result in catastrophic damage to an engine.

The oil pipe junction block connections described here are only for Triumph unit 650s. No less an authority than Mr. Pete informs us that connections for pre-unit Triumphs are the exact opposite.

In the following descriptions of oil line connections, "front" and "forward" reference towards the front of the motorcycle, and "rear" and "back" reference towards the rear of the motorcycle.

Feed Oil Line

The feed line is the rear oil line connection on the oil tank (union nut). The feed line goes to the forward connection pipe on the oil junction block. So oil tank rear to oil junction block forward. (Refer to illustration just below).

Return Oil Line

The return oil line is the front connection on the oil tank. It goes to the oil junction block's rear connection pipe. So oil tank front to oil junction block rear. (Refer to illustration just below).

Illustration of Triumph oil line connections without an external oil filter

Oil Line Connections When Using a Norton Filter Head

Traps!Incorrect installation of oil lines will result in catastrophic damage to an engine.

A Norton oil filter head is ordinarily installed in the return oil line as per the following diagram. Illustration of Triumph oil line connections for add-on oil filter

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Removing Oil Lines at Oil Junction Block

Removing the oil lines from the oil junction block tubes can be a bit difficult, especially if they have been undisturbed for a long time. The job can be made a little easier by removing the outer gearbox cover first.

In any case, it is wise to heed the WS Manual's explicit warning to avoid over-stressing the tubes.

Crankcase Breather


Parts iconFig.2 Crankcase

Parts iconFig.23 Oil Tank

WWW icon "Crankcase breather check?" A real pro tells how to test the engine's disc breather.

A 3/8" plastic tube (70-5375 Ref# 39 Fig.2 #7) connects the engine breather pipe stub (70-2724 Ref# 7 Fig.2 #7) just forward of the gearbox sprocket to Tee (70-5370) near the top of the oil tank. Also connected to the tee is the oil tank vent pipe ( 70-6356, Ref# 16 Fig.23 #7), and the oil breather vent tube (82-7353, Ref# 18 Fig.23 #7) which leads to the mayonnaise dispenser at the back of the rear fender.

Oil Breather Vent Tube

The oil breather vent tube passes on the left side just above the indentation in rear fender.

The first clamp is fastened on the left-hand side beneath the left nut holding the strap on top of the fender between the two upper shock mounts.

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Oil Pump


Icon for manual Workshop Manual (1969 650cc Twins) Section B33: Remove/Replace Oil Pump

Icon for manual Workshop Manual (1969 650cc Twins) Section A7: Stripping and Reassembling the Oil Pump

manual icon Triumph Overhaul Manual Assembling the Oil Pump

Parts icon Fig.3 Oil Pump

Photo icon  Oil Pump

WWW icon "Oil Pump Confusion Unit 650cc SOLVED!"

Compatibility   Although Triumph made several changes to 650/750 oil pumps, they are all interchangeable according to John Healy.

Year Part No Specs
1963 - 1966 E3878 Scavenge 0.437"/ Feed 0.374"
1967 - Early 1969 E6928 Scavenge enlarged to 0.487"/ Feed 0.374"
Late 1969 - 1979 E9421 Scavenge 0.487"/ Feed enlarged to 0.406"
1980 and on 71-7317 Double check-valve pump
(Scavenge& Feed unchanged: Scavenge 0.487"/ Feed 0.406")
Source:, "Oil Pump Confusion Unit 650cc SOLVED!"

Oil Pressure Relief Valve


Icon for manual Workshop Manual (1969 650cc Twins) Section A5: Oil Pressure

Icon for manual Workshop Manual (1969 650cc Twins) Section A6: Stripping and Reassembling the Oil Pressure Release Valve

manual icon Triumph Overhaul Manual Assembling the Oil Pressure Relief Valve

Parts iconFig.3 Pressure Relief Valve

Oil Pressure Switch


Icon for manual Workshop Manual (1969 650cc Twins) Section H18: Oil Pressure Switch

Parts iconFig.6 Timing Cover

WWW icon TriumphRat forum oil switch thread discussion excerpt.

If so desired, the oil pressure switch can be removed and replaced by a blanking plug.

When fitting a blanking plug or a replacement oil switch, be certain that you have the correct part because on some models the threads in the timing cover are straight and in others they are tapered. See discussion linked to above.

Traps! Using the wrong part can result in a cracked timing cover!

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The Oil Tank


Icon for manual Workshop Manual (1969 650cc Twins) Section E2: Removing and Replacing the Oil Tank

Parts iconFig.23 Oil tank

Icon for photo Battery Carrier/Oil Tank Mounting (2 photos)

Icon for WWW A thread with some interesting info on oil tanks, oil pumps, and oil flow

WWW icon A thread on repairing Triumph oil tanks

WWW icon Another oil tank repair thread

WWW icon Some ideas on cleaning oil tanks

Problematic Oil Tank Design - 1966

CompatiblityFrom 1967 to 1970 the unit 650 Triumph oil tank was unchanged. However, according to RF Whatley, Triumph made several modifications to engine lubrication in 1966, including a new (and problematic) oil tank design. Whatley says use of the modified design was limited to several months of production and most were changed under warranty. However, an oil tank with the rocker feed coming off the top instead of the bottom is of the problematic 1966 design and should be replaced with a later model.

Removing Oil Tank

  1. Undo hoses
  2. Remove rubber-mounted screw-headed studs and nuts that go through the two top mounting tabs of the oil tank

    Punching them out through the rubber won't work well - use the water pump pliers to pop them out

  3. Battery holder must be removed before oil tank
  4. Remove bottom mounting bracket
  5. Removing oil tank: swing bottom outward allowing the tube sticking out of the froth tower to slide over the top of the frame bracket

Replace Oil Tank

Use Murphy's Oil soap on the rubber parts.

Oil Tank Mounting Adjustment

Important that tank "hangs" well or wear will occur.

One would think that the rubber mounting would incur the wear, but after my first re-assembly there was wear and it was to the tank's mounting peg, not the rubber.

A comfortably loose configuration, adjusted by turning the "C" clamp mounting bracket, should work.

Oil Tank Mounting Measurements

In case you ever need to know, HenryAnthony on forum informs us that the measurement between the barrels holding the rubber upper mounts is 4-1/4", and the measurement between the battery holder straps they bolt up to is 4-1/2".

Wet Sumping


Icon for manual Workshop Manual (1969 650cc Twins) Section A21: Check Procedure for Wet Sumping

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Primary Chaincase Lubrication


Icon for manual Workshop Manual (1969 650cc Twins) Section A12: Primary Chaincase Lubrication

Owners of Models Late-1969 & On - Read This

Compatiblity Information presented below does not pertain to engines made after late 1969. Up until that time crankcases and primary chaincases were entirely separate from each other and each had its own oil supply. But in late 1969 Triumph modified the way the engines breathed, and in so doing, crankcases and primary chaincases were vented to each other and began sharing the same oil supply.

Since Triumph introduced the changes in late 1969, they weren't documented in parts books and manuals until 1970. Consult books beginning with 1970 if your model is a late 1969 that shares oil, or a 1970 or later.

Oil Change

Change primary chaincase oil at 1,000 mile intervals. Drain and replace with 350cc of 30w non-detergent oil.

Draining the Primary Chaincase Oil

The chaincase oil drains slowly because it needs to flow past the primary chain tension adjuster. The drip, drip, drip flow of oil even when it's hot takes hours so I usually give it all day or overnight.

  1. Put wooden blocks beneath the front wheel to tip the chaincase for better drainage.
  2. Remove the drain bolt using an offset 7/16" box end reversed to avoid interference with the frame bolt there.
  3. I use a funnel and a 400ml graduated plastic cup and keep an eye on the amount of oil that drains out.

After replacing the drain bolt, pour 350ml of 30w non-detergent oil into the inspection cap on top of the chaincase.

Traps! Avoid damaging threads in the soft aluminum case, go easy tightening the drain bolt.

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Gearbox Lubrication


Icon for manual Workshop Manual (1969 650cc Twins) Section A11: Gearbox Lubrication

WWW icon "The Effects of EP Additives on Gearboxes"

WWW icon Lucas oil representative 'Don't use our products with yellow metal' (2014)

WWW icon "Bronze-friendly gear oil recommendation?"

WWW icon Comments & recommendations (UK & US) on crankcase oil/ZDDP (zinc) and gearbox oil/yellow metals

WWW icon Hermit's Gearbox Oil/Yellow Metal Experiment, with conclusion.

Gear Oil Compatibility

Opinions differ about using GL5 spec gear oils around the yellow metal bushings and thrust washers used in our Triumph gearboxes.

GL5 oils have high concentrations of sulphur and sulphur reacts with yellow metals chemically to break them down. So say those who believe GL5 is harmful. Yet many others say they've used GL5 for years without problems.

Why take a chance? I was always disinclined to use GL5 gear oil in my Bonnie's gearbox.

Oil companies say GL5 products are now safe because they've reduced active sulphur, which eats yellow metals, in favor of inactive sulphur, which is less harmful while still providing the protective qualities of active sulphur.

I don't find "less harmful" all that reassuring, frankly.

However, since doing my own yellow metal and GL5 experiment I do feel a bit more comfortable about GL5. But I still prefer good old GL4.

Potentially Harmful Products

For those who harbor doubts, the following list of oil descriptions are those which are said to be, at least potentially, harmful to yellow metals:

For other gear oil recommendations (including many in UK) see this link above in TriumphRat.

Oil Change Schedule

Draining and Replenishing the Gearbox Oil

There are three hex heads on the bottom of the gearbox: the 3/4" index plunger holder (57-2172); the 7/16BS (3/8W) drain plug with level tube (57-3851); and the 5/16" gearbox level plug (21-0543).

The level plug threads into the drain plug and together they are tucked just inside the frame member on the timing side. Since they are closer to the timing side I always removed and installed them from that side. However, access from that side is awkward due to the proximity of the frame, and recently I realized that it's actually easier to access them from the drive side.

To drain the oil, remove the drain bolt using a 7/16BS (3/8W) socket and a two or three inch extension to clear the frame. Remove carefully to avoid damage to the level tube extending above the drain bolt.

When replenishing the gearbox oil, replace the drain plug after removing the level plug and then add oil, slowly when approaching 500ml, until it overflows from the level plug.

Oil Leaking from Drain Bolts


WWW icon " How to stop oil and gear box drain plug leaks?".

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Front fork


Icon for manual Workshop Manual (1969 650cc Twins) Section A16: Front Fork Lubrication

Draining Fork Oil

Tips iconGavin Eisler's tip on draining fork oil:
"When changing fork oil remove RHS top nut, remove LHS drain screw, doing opposites stops oil gushing out the top as the bike settles. Read that in the manual, after doing it wrong for years, this saves a lot of mess. I like to flush the old oil with a little kerosene to get the last of the muck out."

Contact Breaker Assembly


Icon for manual Workshop Manual (1969 650cc Twins) Section A10: Contact Breaker Lubrication

Speedometer Gearbox

Swinging Arm Bushing

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The Engine


Icon for manual Triumph Overhaul Manual 650cc Unit Construction Triumph Engines since 1963

manual icon Triumph Overhaul Manual List of Engine Changes Relating to Major Engine Work

manual icon Triumph Overhaul Manual Triumph Tools Needed for Complete Overhaul

Parts iconFig.2 Crankcase

Parts iconFig.14 Engine Mounting Plates, Footrests

WWW icon "Torque wrench settings", Rod bolt stretch, tappets & cams

WWW icon TR7RVMan's advice on preparing for a complete engine tear down

WWW icon Engine Rebuilding Guys in the know tell us what to look for when rebuilding an engine (must-read)

WWW icon Triple Cycles, UK "Waking the Sleeping Beast" Starting an engine after a long sleep. Note: this article was written for Triples. StuartMac cautions us to add just one pint and not two to a Twin's craankcase through the primary chaincase since its crankcases is smaller,

Pre-Ignition & Detonation


Video icon  CycleWorld "What Is The Difference Between Normal And Abnormal Combustion In A Motorcycle Engine?" An overview.

WWW icon  Allen W. Cline, CONTACT! Magazine "Engine Basics: Detonation and Pre-Ignition" Detailed explanation.

Above video and article (suggested by Truckedup on both explain pre-ignition and detonation and the difference between them. If I've got it right:

Tip! "Generally detonation witness marks are not left in the center of the piston, they tend (note:I did not say always) to show up at the edge of the piston. Light detonation can most times be tolerated by a piston, heavy detonation often collapses the piston ring lands." Peg, on

Tip! "Marks in the center of the piston are more likely to be the result of Pre-Ignition, a much more sinister problem. This problem tends blows holes in your piston crown, it destroys in seconds. (Pre ignition can be brought about by the heat generated by detonation)." Peg, on

Things to beware of:

Kicking Back When Starting

Kicking back during starting is not only potentially hazardous to a rider, it is often a symptom of engine problems. Three of the most likely causes of kick-back are:

When considering timing advance issues it's wise to first check the alignment of the rotor's 38 degree line with actual TDC using a TDC tool or other method.

Spin speed can be a factor, particularly in the case of electronic ignition systems.

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Engine Removal and Installation


Icon for manual Workshop Manual (1969 650cc Twins) Section B1: Removing and Replacing the Engine Unit

Photo icon Removing engine using chain hoist

Photo icon Removing engine using floor jack & muscle

Illustrtion of Triumph engine mounting hardware

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manual icon Triumph Overhaul Manual Assembling the Flywheel

Icon for World Wide Web MB walks us through Triumph "Flywheel Evolution"

The three flywheel bolts are one of the four places to use Loctite on a Triumph, and the only place to use red Locktite.

Compatiblity Triumph made numerous modifications to the "B"-range flywheels between 1963 and 1971. As summarized below, MB listed major changes in the thread "Flywheel Evolution" (link above).

1963 to 1971 - Changes to Triumph Flywheels
Heavyweight flywheel - no timing slots
1965 Slot for TDC added
1966 Lightweight flywheel
Balance factor unchanged (85%)
1968 Lightweight flywheel
Slot for 38 degree max advance timing added
First ones also had extra slots for timing plug re-positioned to the front of the engine, but later reverted to rear position after DU74052
1969 Began w lightweight flywheel
Reverted to heavyweight at NC.02256 - much like 1965 flywheel, but with 38 degree slot
1971 New flywheel - different profile
Same balance factor and slots as 1969 flywheel
Metric-sized timing side crank introduced at end of 1971 model year

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Icon for manual Workshop Manual (1969 650cc Twins) Section B39: Inspect Crankcase Components

manual icon Triumph Overhaul Manual Separating Crankcase Assembly

manual icon Triumph Overhaul Manual Assembling the Crankcase Halves



Icon for manual Workshop Manual (1969 650cc Twins) Section B36: Dismantle/Reassemble Crankshaft Assembly

Icon for manual Workshop Manual (1969 650cc Twins) Section B37: Stripping & Reassembling the Crankshaft Assembly

manual icon Triumph Overhaul Manual Measure crankshaft journals

Icon for manual Service Bulletin #67-15 "Roller Bearing (E2879) Crankshaft Drive Side on "B" Range 650cc beg.DU24875"

Icon for manual Service Bulletin Twin 14/72 "Metric Main Bearings"

WWW icon "Triumph Main Bearings Used by Year and Model" Info on C2, CN, C3

WWW icon "Weight of a 650 crank" Very informative thread!

Video icon YouTube Lunmad - 650 bottom end inc sludge AND easy gearbox assy All under 20 minutes.

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Sludge Trap


Icon for manual Workshop Manual (1969 650cc Twins) Section B37: Stripping & Reassembling the Crankshaft Assembly

manual icon Triumph Overhaul Manual Installing the Sludge Trap

WWW icon "Removing Trumph Sludge Tube"

WWW icon "How to Remove the Trumph Sludge Trap Tube"

The sludge trap is a metal tube fitted inside the gallery that runs through the big end connecting rod journals. Oil is forced through the timing end of the crankshaft and through oil passageways into the sludge tube. There, centrifugal force separates the particles suspended in the oil - think of a washer in spin cycle with bras and panties flattened while the water flows away. Well, maybe not such a great analogy. Anyway, inboard weep holes permit the oil to lubricate the big end bearings and then return to the crankcase sump from where it's pumped back to the reservoir.

Although it's controversial and frequently maligned, the Triumph sludge trap is actually a relatively effective oil filter. Its big drawback is that it can't be inspected or cleaned without splitting the crankcase - a major job requiring complete disassembly of the transmission and engine, although not necessary the gearbox.

Some believe that no matter how full the sludge tube becomes, oil under pressure will always make its way to the big ends.

That's a theory, but the more widely accepted notion is that a plugged sludge tube will prevent oil from flowing to the big ends with catastrophic results.

It's also widely held that after a bike sits for a long time and is then restarted, dirt particles in the tube may break off and subsequently block critical oil ways in the engine, there being more risk for machines lubricated with non-detergent oil before storage and then drained and re-filled with detergent oil before re-starting.

So without splitting the cases, how does one know whether or not the sludge tube needs cleaning/replacing? Unfortunately we can't answer this question precisely, we can only make an educated guess based on service history and engine condition.

More Sludge Deposit Less Sludge Deposit
High mileage Low mileage
Using non-detergent oil Using detergent oil
Running dirty oil Frequent oil changes
No external oil filter (as stock) Fitting external oil filter

A sludge trap service interval of twenty- to forty-thousand miles seems about right for a well-maintained machine in good condition and fitted with an external oil filter. Without an oil filter (stock) one could expect a significant reduction of those figures.

On the other hand, it has been said that fitting an external oil filter quadruples the life of an engine, and it's certainly not unreasonable to expect that a sludge trap would fill more slowly under those circumstances.

Some suggest hypothetically that sludge traps on '70 and onward 650 Twins might fill up more quickly due to those models sharing oil between primary chaincase and crankcase and on the basis that the clutch produces even more sludge (think shock absorber rubbers) than the engine itself.

Sludge tubes can be quite difficult to remove as there are two hurdles: removing the cap, and removing the tube itself. Tubes don't always survive the extraction, caps rarely. However, replacement sludge tubes are not expensive. Also, caps for them are now available which have either hex heads or hex key sockets instead of the more difficult to remove slotted head on the stock item.

There are two ways to remove the tube: smack it out and pull it out. Pulling it out may contribute to higher rates of tube survival.

What size tap to use for (smack it out) tube removal? LowBrow video (link above) suggests 3/8"-18 N.P.T.

When replacing the sludge tube be absolutely certain that its alignment hole is actually lined up for the flywheel bolt before inserting and tightening the bolt (Grand Paul).

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DS Crankshaft Oil Seal


Manual iconTriumph WS Manual Illustration of correct DS crankshaft seal orientation

Manual iconTriumph Overhaul Manual DS crankshaft oil seal

WWW icon John Healy's explanation for orienting DS oil seal with spring towards primary chaincase

When replacing the DS crankshaft oil seal, note that there are differing opinions floating around as to its correct orientation. In spite of both the Triumph Workshop and Overhaul manuals clearly indicating that the spring side of seal should face the engine sprocket (outwards), there are those who insist this is incorrect. See the link just above.

Compatiblity We should also note that, due to a different crankcase breathing method, 1970 and 1971 models are not, and should not, be fitted with the DS oil seal, even though the Replacement Parts Catalogues for those years erroneously illustrate and list it.

The following table summarizes the main points raised in the discussion above, though it is probably worthwhile to read the entire discussion.

Year Engine Breathing Crankcase/
DS Crankshaft Oil Seal
1963 - 1969 Timed engine breather Engine/Primary oil not shared Oil seal required. Springs to engine sprocket
1970 - 1972 Breathes via 3 holes btwn crankcase & primary chaincase Engine/Primary oil shared NO oil seal should be used, even though erroneously shown in the parts books (J Healy)

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Main Bearings


Icon for manual Workshop Manual (1969 650cc Twins) Section B40: Renew Main Bearings

manual icon Triumph Overhaul Manual Installing the Connecting Rods

Icon for manual Service Bulletin Twin 14/72 "Metric Main Bearings"

Connecting Rods


Icon for manual Workshop Manual (1969 650cc Twins) Section B38: Refit Connecting Rods

Icon for manualTriumph Service Bulletin #317 "Self-locking nuts on big ends" (as shown in #7).

Parts icon Fig.1 Connecting Rods

WWW icon "Unit 650 con rods" Discussion on re-using con rods versus replacing with new ones.

CompatiblityIn either in 1967 (DU47006) 1  or June 1969 (GC23016) 2 , Triumph introduced new connecting rods (70-9525) that were thicker and stronger at the small end than the older ones (E3606/E3606T). Also, the new units were fitted with UNF bolts and self-locking nuts. To accomodate the new thread form, the torque was reduced from 28lbs/ft to 22lbs/ft.

Tightening the Connecting Rod Big End Bolts

Much has been written about tightening the connecting rod nuts and bolts. Mr. Pete ran down all the essentials in a couple of posts to this thread. The incomparable Mr. Pete:

"Don't waste your time using Loctite on conrod nuts. Either tighten them up dry to 22ft-lbs (not 28 ft-lbs!), and risk thread damage on dry threads; or lubricate the threads with oil and measure the elastic bolt extension (0.004"-0.005"). Bolt extension is a better indication of bolt tension than torque measurement. The actual pre-load on the bolt is what is important.

The best way to tension rod bolts is to measure them with a micrometer. It will be easier if you flatten off the ends of the bolts. Measure the bolt before you start tightening. Use a torque wrench to tighten the bolt a little,and measure it again. Each time you tighten it, it should require a little more torque to move the nut. If the torque ever stops increasing,you have a problem and you should loosen the bolt and check its length. It should be the same as when you started or the bolt is junk.

When the bolt reaches 0.004"-0.005" extension, it's tight enough. If you plan to race it, go for 0.005" but no more.

If you can't get use of a micrometer, just tighten the nuts up dry with a torque wrench to 22ft-lbs."

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Timing Chest


Icon for manual Workshop Manual (1969 650cc Twins) Section B32: Remove/Replace the Timing Cover

manual icon Triumph Overhaul Manual Timing Chest, Removing & Inspecting

manual icon Triumph Overhaul Manual Timing Side Assembly

Parts iconFig.6 Timing Cover

WWW icon " Timing cover removal '72 T120R" RPW, Codeman, and Rambo tell you everything you need to know to accomplish this delicate procedure with aplomb.

WWW icon Removing & Replacing the Patent Plate Direct link to useful tips from TR7RVMan buried in a kickstarter thread

Icon for left-handed thread Inlet camshaft nut 70-1463, and Exhaust camshaft nut 70-4563 have left-handed threads. (Ref.33/34 Fig.1 P.13 #7)

Removing the Crankcase Pinion Gear


Icon for manual Workshop Manual (1969 650cc Twins) Section B34: Extract/Refit Valve Timing Pinions

Icon for manual Workshop Manual (1969 650cc Twins) Section B41: Renewing Camshaft Bushes

WWW icon 'Crank pinion gear' Discussion of techniques to remove the crank pinion gear

The difficulty in removing the nut securing the crankcase pinion gear is keeping the gear from moving. That is the topic of discussion in this thread. In it, a solid group of posters propose and debate a variety of methods:

For a novice mechanic like myself, the 'jamming the gears' techniques have too much potential for disaster, even though they may be ok in more experienced hands. Similarly, barring the small ends may not be quite as simple as I have always thought.

I will definitely try remembering to loosen the pinion gear nut FIRST next time. I'll also try remembering first to put the gearbox in neutral and try the impact wrench to see how well that works.

Valve/Cam Timing


Icon for manual Workshop Manual (1969 650cc Twins) Section B35: Valve Timing

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Icon for manual Workshop Manual (1969 650cc Twins) Section B22: Removing and Refitting the Pistons

Icon for manual Workshop Manual (1969 650cc Twins) Section B24: Inspecting Pistons & Cylinder Bores

Icon for manual Workshop Manual (1969 650cc Twins) Section B25: Table of Suitable Rebore Sizes

Icon for manual Workshop Manual (1969 650cc Twins) Section B26: Piston Identification

Parts icon Fig.1 Pistons

Photo icon Removing Pistons

WWW icon "T120 Pistons" (Manufacturers)

WWW icon "New pistons question" John Healey checks in on piston taper and diagnosing piston problems.

WWW icon  Franz and Grubb "Triumph 650 piston installation notes"

Compatiblity New Hepolite pistons were introduced in 1969. The new pistons had a heavier crown and used shorter grudgeon pins with heavier cross sections.

Removing Gudgeon Pins & Pistons

Traps!When working around the connecting rods, use plenty of padding to protect them from the sharp edges of the crankcase and the base studs.

Gudgeon pins are supposed to be a somewhat tight fit in the pistons and move freely (but without side-to-side play) in the small end bushes, Sometimes the pins can be removed with just thumb pressure at room temperature, but it's often necessary to heat the pistons slightly - around 100C with a digital laser thermometer or the spit sizzle method. I have also packed snow in plastic bags around the pistons to chill the gudgeon pins before heating up the pistons.

If a pin won't come all the way out even after heating the piston, you can use a simple extraction tool fashioned from a threaded rod, a couple short lengths of pipe, and some nuts and washers.

Photo icon Simple gudgeon pin extraction tool.

Traps!As noted in the WS Manual, the use of a drift to remove a gudgeon pin is NOT recommended.

Traps!In rare cases when the bushes require reaming that is best done with the connecting rods removed from the engine so that they can be reamed perfectly perpendicular to the connecting rod.

Replacing Gudgeon Pins & Pistons

Chilling the gudgeon pins may be all that's required for them to go in the pistons and bushes, but if necessary heat the pistons as described just above.

Replacing circlips:

  1. Position one end into the groove in the piston
  2. Place thumb over them
  3. Use angled needle-nose pliers to put in the other end
  4. - Bend as little as possible! -

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Icon for manual Workshop Manual (1969 650cc Twins) Gen Data & Sec B23 (obsolete)"

manual icon Triumph Overhaul Manual (1967) Ring Gap (obsolete)

Icon for manualTriumph Service Bulletin #323 "Piston Ring Gaps" (obsolete)

Icon for manualTriumph Service Bulletin (Twin) 1971 "Piston Ring Replacement"

WWW icon  Franz and Grubb "(Grant) Triumph piston ring installation notes"

Ring Gap

Different Triumph docs gave different ring gap specifications. The last revision was made in 1971. Musta been some kinda office lottery or sump'n.

Document When Recommendation
Triumph Service Bulletin (Twin)11/71 1971 0.012 - 0.018
Triumph Overhaul Manual 1967 0.010 - 0.017
Triumph Service Bulletin #323 "Piston Ring Gaps" 1967
0.015 - 0.020
Workshop Manuals, in Gen Data and Section B23 1963 - 1969 0.010 - 0.014

Installing Rings

Always install rings from the top and observe correct order and cylinder for each ring. Orient the oil scraper rings with their gaps at six o'clock, and the compression ring gaps at three o'clock and nine o'clock.

One advantage of using ring compressors is that the orientation of the ring gaps doesn't change during installation.

Also See: John Healy on "dry" ring assembly.

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Cylinder Block & Tappet Blocks


manual icon Triumph Overhaul Manual Assembling Pistons, Pins, Rods, Cylinder Barrel

Icon for manual Workshop Manual (1969 650cc Twins) Section B20: Inspecting Tappets & Guide Blocks

Icon for manual Workshop Manual (1969 650cc Twins) Section B21: Renewing the Tappet Guide Blocks

Icon for manual Workshop Manual (1969 650cc Twins) Section B19: Removing and Replacing the Cylinder Block and Tappets

Parts iconFig.5 Cylinder Block

Parts iconFig.3 Tappet Guide Blocks

WWW icon  J.R.C. Engineering "Understanding Triumph Tappet Blocks and Pushrod Tubes" Complete rundown of tappet blocks & PRTs on Triumph models from 1945-1982

Cylinder Re-Bore


WWW icon "Which Comes First, Piston or Bore?" Long, interesting thread, with broad con census on best procedure to follow, and many tips on re-boring a Triumph unit 650.

WWW icon "Mapping the bore" An experienced hand explains how to prepare for a cylinder re-bore. Learn some very interesting facts about cylinder topography and piston shape in the process.

WWW icon "Dry Ring Installation" A repost of John Healy describing the complete Triumph 650 honing process, followed by his take on "dry" ring assembly - or, as Mr. Healy would prefer, "dri-er" ring assembly.

WWW icon "Further to preparing the cylinder..." Mr. Healy offers more fine points on honing Triumph 650 cylinders, and dives deeper into the machinations of air-cooled machines.

Honing Cylinders

Before the next time you have a shop hone your Triumph 650 cylinders, it's well worth your time to read the above posts by John Healy on the tried and true methods of getting a good re-bore and a good break-in.

After honing, cylinders need to be washed and scrubbed with a brush in hot water with detergent to remove ALL remaining abrasive material. It can't be over-emphasized how important this is. Wash them and wash again. And again. Foreign materials left behind may score the cylinders or block oil-ways, ruining the entire job with potentially catastrophic results.

When thoroughly clean, dry the cylinders with a clean cloth and then apply light coat of oil.

Replacing Tappet Guide Blocks


Icon for manual Workshop Manual (1969 650cc Twins) Section B21: Renewing the Tappet Guide Blocks

WWW icon "Refitting tappet guide block, T140" TR7RVMan nails the drill (pertains also to T120)

WWW icon "Tappet block installation" Koan58 offers a method for precision alignment.

To remove or replace the tappet guide blocks it's essential to use the special drift: Service Tool 61-6008. It takes substantial blows with something like a little two-pound sledge to drive the blocks in. While a block is moving, it can be steered quite easily by twisting on the tool's hatch-marked handle.

Tip!When driving the guide blocks in or out, remember that they are not perfectly vertical - they are set at a slight angle. Adjust your drift accordingly or risk damaging the block's skirts. Ask me how I know.

On his DVD, Hancox says to line up the hole in the blocks with the locator screw hole in the cylinder block. For an amateur like myself that's not a sufficient guarantee that the tappet holes will end up exactly parallel to the camshaft. Instead I try to concentrate on the alignment of the tappet holes with the camshaft - if that is acheived the locator screw will line up for sure.

Tip!Being relatively narrow, the tappet blocks are difficult to line up perfectly by eye. For best results, use a straight edge placed against the block.

Illustration of correct orientation of Triumph exhaust tappet
 guide block

Replacing Tappets

New guide blocks frequently require honing before the tappets will ride up and down freely.

Traps!For the exhaust tappets to be properly lubricated, they must be installed in the tappet block with their "flats" ("C" in illustration at right) facing outward.

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Replacing Cylinder Block

Removing old gasket material is an annoying job. Using a gasket remover product is probably a better alternative than scraping with razor blades. Loctite makes two such products 1) Loctite 'paint remover', and 2) Loctite 790 'Chiselr Gasket Remover'. Afterwards clean the surfaces with acetone.

Tightening Cylinder Base Bolts

Can't get on the block nuts with a torque wrench, but using a 6-inch 12-point box wrench (1/2") to tighten them as hard as possible will approximate the proper torque of 35lbs.

Painting Cylinder Block


WWW icon Cylinder paint recommendations?.

Unquestionably, the best-looking and longest-lasting finish for the cylinder block is powder coat. For tips on other products and surface prep see link above.

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Cylinder Head


Manual icon Workshop Manual (1969 650cc Twins) Section B14: Removing & Refitting the Cylinder Head Assembly

manual icon Triumph Overhaul Manual Cylinder Head, Remove & Inspect

manual icon Triumph Overhaul Manual Assembling the Cylinder Head

Parts iconFig.5 Cylinder Head

Anneal and Install Head Gasket

Perfectly fine to reuse the copper head gasket as long as it is in good shape and properly prepared.

Begin by removing any burring that appears on the gasket. Burrs near the cylinders may create hot spots that can promote pre-ignition.

Next, always anneal a used head gasket before use. Some will even anneal new gaskets just to be sure. Annealing the gasket softens the copper and allows it to create a better seal between the head and the cylinders. The annealing process is simply heating the gasket cherry red and then plunging it into a container of water. If your heat source won't heat the entire gasket cherry red at the seme time it is ok to anneal the gasket one section at a time - just be sure every part of the gasket has been annealed.

Heating the gasket red hot often causes oxidation to form on the surface, particularly if it is heated multiple times. The oxidation probably doesn't affect the gasket's sealing properties, but as John Healy says, removing it makes for a more professional-looking job. Soaking the gasket in vinegar overnight will turn most of the oxidation into a brown "fluff" which can be rinsed off with water.

Apply grease or Permatex Copper Coat to both sides of the head gasket before installing. Using a sealing agent helps prevent oil leaks as well as compression leakage between cylinders.

Anti-Seize Compound

Although using anti-seize compound for head bolts and spark plugs is in some ways a good idea, it has two down sides. First of all, head bolt torque figures are given for dry threads, so they need to be revised downward when using anything on the threads.

Secondly, the anti-seize compound leaves behind considerable messy residue which must be thoroughly cleaned off during the next disassembly.

A cleanup method that works well is to fill the bolt holes with kerosene or brake cleaning fluid and then run the bolts in and out while using a rag to mop up solvent and crud as they run out past the threads. When the bolt bores are good and clean, clear them with compressed air.

Installing Cylinder Head & PRTs

See Installing Pushrod Tubes & Cylinder head below.

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Head Bolt Torque


WWW icon "T120 8-stud head torque"

The correct head bolt torques for unit construction 650s are 15lbs./18lbs.: 15lbs. on the 5/16" bolt (#1), and 18lbs. on the 3/8" bolts (#s 2-3-4-5-6-7-8).

Trap!Be aware that you may also see the torque numbers 18/25. This erroneous set of higher numbers originated in the 1966 Triumph WS Manual, and although it was quickly corrected in a Triumph service bulletin, it apparently lived on, uncorrected in other documentation, including the Triumph Overhaul Manual. (John Healy).

The higher torques may look attractive to some, as they may find 15/18 too low. But it must be remembered that the torque will effectively rise as the cylinders and head heat up and expand. Over-torquing (beyond 15/18) can result in indentations to the alloy head beneath head bolt washers. Extreme over-torquing can result in a cracked head. Cracked head, no good!

Torquing the Head-Bolts

Torque figures given are for dry threads. One recommendation is reduce by 20% when wet. So for example, if using anti-seize compound, one would use 15lbs instead of 18. When I've used anti-seize compound I confess I've still used the 18 lb figure. Triumph 650 head bolts

The head bolts are tightened in the order 1-2-3-4-5-6-7-8-9 as shown in the accompanying illustration, and the final torque rating is reached by incremental steps. For example, tighten all the 18 lb torque bolts to 10 lb, and then 14 lb, and finally 18 lb.

On his DVD, Hughie Hancox starts with bolt #1 and tightens each bolt one by one right to their final torque figure. I tried that method in 2006 and it worked ok, but I feel more comfortable using the incremental 'round robin' method.

The 1/4 inch rocker box bolts and the rocker box stud nuts are torqued to just 5 pounds. Be careful. Install bolts and nuts at least finger tight before torquing head bolts. Doesn't hurt to tighten these fasteners incrementally among themselves and in conjunction with the head bolts. In the end the three nuts can be loosened slightly and re-tightened to obtain an identical torque.

Re-Torquing Head Bolts

After the first heat cycle(s) when the head has been removed and replaced, the head-bolts must be re-torqued to compensate for their looseness due to the "bedding-in" of the cylinder gasket, cylinder head, and bolts.

Because torque figures pertain to bolts when they are turning, it's not effective to just start tightening them. That would most likely result in over-torquing, which is never a good thing. So, the method is:

Note that the bolts don't actually loosen themselves, they loosen relatively, due to compression of the head gasket and stretch of the head bolts. Nevertheless, the question arises in many minds, were the bolts actually "loose" before re-torquing, and if so by how much? One way to find out is to mark one point of each head bolt and then make a corresponding mark on the head. After you re-torque you'll see whether it was necessary to re-tighten each bolt.

And as the "Duke of Oil" pointed out on, given their thread factor and how far the bolts turned to get back to spec it's possible to calculate how much the head gasket compressed and the head bolts stretched.

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Rocker Boxes


Icon for manual Workshop Manual (1969 650cc Twins) Section B2: Removing and Replacing the Rocker Boxes

Manual icon Workshop Manual (1969 650cc Twins) Section B3: Inspecting Pushrods

Manual icon Workshop Manual (1969 650cc Twins) Section B4: Strip/Reassemble Rocker Boxes

Parts icon Fig.5 Rocker Boxes

Rocker Arms, Rocker Shafts, & Thackary Washers


Manual icon Triumph Service Bulletin #25 "Lubrication - Rocker End, Ball Arm"

WWW icon Retrofitting updated rocker box components ('Calling John Healey or someone that can answer')

WWW icon 1973 T140 rocker spindles. Oil grooves?

WWW icon Rocker shaft spring washer location??.

WWW icon 71 T100R and the Thackeray Unpleasantness

Thackary. As pointed out by one poster: rhymes with 'quackery'. And have you ever wondered how Thackary washers got their name? Ian Peters on "More To The Name" has quite an interesting story about its origins. But I digress.

Pending Edit

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Rocker Spindle Washer Order Illustrated

Early Washer Order

Triumph rocker arm, rocker spindle, and spindle washers illustration

Starting from TS, the original #7 layout used with plain rocker spindles

Updated Washer Order

The updated layout for use with grooved spindles & notched rocker arms: Triumph rocker arm, rocker spindle, and spindle washers illustration

Removing the Rocker Boxes

Not strictly necessary to remove the ignition coils, but we want to polish them up anyway, right? After removing gas tank, torque stays, and the domed nuts and copper washers from the oil lines, gradually release the torque from and remove:

Assembling & Replacing Rocker Arms & Rocker Spindles

As per WS and Hanyes manuals, I used a 5/16" bolt ground to a taper at one end to help line up the flat and spring washers before inserting the spindles. With enough fiddling around they eventually go on.

If a spindle doesn't go quite all the way in it is probably due to the last washer (DS) hanging up on the rocker spindle's shoulder. Play with the washers and tap very lightly on the end of the spindle with plastic mallet. When everything is lined up it takes only a light tap.

Rocker Arm Spindle O-Rings


WWW icon Ed Holin "What is the correct O ring for the rocker spindles on a '71 Triumph T100R and similar bikes?".

WWW icon TriumphRat Tips on installing and sealing the spindle o-rings.

When replacing the rocker shaft o-rings (ref#29 Fig.5 #7), don't use the 70-3253 listed in #7. Use updated, better fitting part 60-3548. And be sure it's Viton.

For what it's worth - Tool icon special tool Z111, rocker spindle oil seal compressor, is available. I've never found it effective or helpful.

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Pushrod Tubes (PRTs)


Parts iconFig.5 Pushrod Tubes

WWW icon  J.R. Engineering "Understanding Triumph Tappet Blocks and Pushrod Tubes" Complete rundown of tappet blocks & PRTs on Triumph models from 1945-1982

Pushrod Tube Styles

Between 1965 and 1972 three different pushrod tubes, each with its own type of seal were used on "B" range 650s. The earlier PRT (70-6000) has a different length than both the later 70-9349 and 71-2575 and as well so they are incompatible with the later cylinder heads and tappet guide blocks.

On the other hand, while the later 70-9349 (fabricated) and 71-2575 (one-piece) PRTs used different seal methods, their lengths were the same, they used the same tappet guide blocks and compatible cylinder heads, so they are interchangeable during those years.

Compatiblity The following table is a simplified summary of the PRTs, cylinder heads, and tappet guide blocks used from 1967 to 1972. For a complete rundown, including the tappet variations, see the JRC Engineering link just above.

  1967 - 1968 1969 - 1970 1971 - 1972
Pushrod tube 70-6000 70-9349 71-2575
Cylinder head 70-7031 70-9418 71-2354
Tappet guide blocks 70-4676 / 70-5861 70-9352 / 70-9353 70-9352 / 70-9353

Pushrod Tube O-Rings


Manual iconTriumph Service Bulletin #18-69 "PRT o-rings leaking oil - 1969 'B' & 'C' Range"

Oil leaks from the pushrod tubes (PRT's) have been a perennial problem for many Triumph owners.

In 1969 Triumph replaced the rubber sealing washers used by earlier models at the top and bottom of the PRTs with o-rings. The new o-rings fit into newly designed PRTs (70-9349) and inlet and exhaust tappet guide blocks (70-9352 / 70-9353). O-rings at the top of the PRTs stood up poorly to the high temperatures there so beginning in 1971 Triumph substituted a different upper o-ring. The new high temperature red 71-1283 o-rings were somewhat a disaster. I used them twice and both times they quickly crumbled to pieces. Later, the 71-1283 o-ring became available in Viton and the Viton units proved to be far more durable.

Meanwhile, in 1971 Triumph introduced a new PRT, the 71-2575. The new PRT continued using o-rings top and bottom, but added a compression seal at the bottom, along with a metal sleeve (aka the "wedding band") to prevent the new seal from squeezing out when compressed by bolting down the cylinder head.

CompatiblityThe following table details the different PRT o-rings specified between 1969 and 1971. Note that the 70-7310 and 71-1283 o-rings are the same size and differ only in their material, therefore Viton 71-1283 o-rings are the logical choice for both PRT's, top and bottom on all the 1969-1972 650 models.

Part/Year #7 ('69) '70 USA '71 USA '72 USA
Bottom o-ring 70-7310 70-7310 70-7310 70-7310
Top o-ring 70-7310 70-7310 71-1283 71-1283
PRT (pushrod tube) 70-9349 70-9349 71-2575 71-2575
Sealing ring 70-4752 70-4752
"Wedding Band" sleeve 71-1707 71-1707

Pushrod Tube Sealing Ring & Wedding Band


Manual iconTriumph Service Bulletin 324 Pushrod tube oil seals

In 1971 Triumph added another oil seal in addition to the o-rings found on the 1969-1970 models. The new "sealing ring" (70-4752) sits between the PRTs and the tappet guide blocks and has a square-section to improve sealing. The "wedding band" metal sleeve fits over the sealing ring and keeps it from being squeezed out of place by the pressure of the cylinder head being tightened down on the PRTs.

The square-sectioned sealing rings are commonly, but not always, white silicon. I've had black, sponge-like seals and they worked fine. These seals come in different thicknesses to enable adjustment of "the crush". (See section below).

Compatiblity The 1971-1972 setup is an easy and highly desirable upgrade for the 1969-1970 650 models. It involves upgrading to the 71-2575 PRTs (completely compatible with 1969-1970 tappet guide blocks and cylinder heads) and adding the sealing ring (70-4752) and metal sleeve (71-1707)

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Pushrod Tubes and "Crush"


WWW icon John Healy, Vintage Bike Magazine "Push Rod Tubes"

WWW icon thread Discussion of PRT 'crush'

WWW icon thread Discussion of PRT sealing rubber protruding

Video icon YouTube Raber's Tech Tips, Episode #3 - Triumph 1967 T120 Bonneville Pushrod Tube Seals

'Crush' refers to the amount of compression of the seals and o-rings at the bottoms and tops of the PRTs respectively when the head bolts are tightened down. Too little crush means the seals are compressed insufficiently to create a good seal, resulting in oil leaks. Too much crush results in the seals holding the cylinders and the head apart and further tightening of the head bolts can cause the alloy head to warp.

When the head is sitting freely (loose bolts) on top of the cylinders with the head gasket and PRT seals and o-rings in place, there should be between .030" and .040" gap between the cylinder head and the head gasket.

If the gap is too wide there will be insufficient crush, resulting in a poor seal and oil leaks. If the gap is too narrow there will be too much crush, risking distortion of the head when head bolts are torqued down.

The gap, and therefore the crush, are adjusted by substituting different thicknesses of sealing rings. A thicker sealing ring holds the PRTs and the head higher, increasing the gap and reducing crush. A thinner seal makes the gap smaller, increasing the crush.

For dimensions of sealing rings & o-rings see table below.

Install head with bolts 6,7,8,and 9 fitted evenly and lightly enough that the bottom seals and top o-rings are not being compressed. Then check for a suitable gap that is even all the way around.

Installing Pushrod Tubes & Cylinder Head

Although one of Bonnie's pushrod tubes seats very tightly at the bottom and the other is relatively loose, they both seem to seal well to the tappet block once the head is bolted down and the sealing ring squashes out to the wedding ring.

Be sure to oil the top and bottom o-rings before assembly (sharp edges ahead). It's also ok and good to grease the top o-rings to help hold in place as well as lubricate.

In 2016, I used 'Right Stuff' on the top o-rings during first assembly. Upon disassembly 450 miles later, I picked the Right Stuff 'slime' out of the o-ring groove. No more 'Right Stuff' for me. Back to oil and grease.

When installing the head, it may go better to maneuver it into place from the rear, as opposed to from one side or the other.

Slight in & out adjustments (punch and ball peen) to the tabs at the top of the PRTs can sometimes ease installation or removal of the PRTs. Just be sure the tabs don't foul the pushrods when they are installed.

PRT O-Ring & Seal Dimensions

When adjusting for proper sealing ring crush, the following dimensions could be helpful.

Component Height
Cylinder Head 2.755"
2.785 (Internet forum)
Head Gaskets .045-.050
Round o-rings 70-7310 (Buna-n) / 71-1283 (Viton)
ID=.987"/Nom 1" CS=.103"/Nom 3/32" OD=1.193"/Nom 1 3/16" Dash#120
Square-sectioned sealing rings 70-3547 Thick= .093"/nominal 3/32" (.095 Raber's)
70-4752 Thick= .125"/nominal 1/8") (.125 Raber's)
70-1496 Thick=.1875"/nominal 3/16" (.177 Raber's)
Pushrod Tubes 70-9349/71-2575

Source: unless otherwise noted, dimensions are from John Healy's article 'Push Rod Tubes' in Vintage Bike Magazine.

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Rocker Box Gaskets


WWW icon "Gasket sealer for top end "

I've used wire-reinforced (BCS and Walridge), plain paper (MAPCycle), and paper & metal sandwich Covseals (Baxter) for rocker boxes. Covseals made the best seal, followed by MAPCycle's plain paper. Wire-reinforced gaskets were my least favorite.

I used the Covseals dry as per included instructions and I noticed some weeping. After reading the post just above I coated the Covseals with Hylomar the next time and the rocker box joints were completely leak-proof.

Replacing Push Rods and Rocker Boxes


Icon for manual Workshop Manual (1969 650cc Twins) Section B2: Removing and Replacing the Rocker Boxes

Manual icon Workshop Manual (1969 650cc Twins) Section B3: Inspecting Pushrods

Manual icon Workshop Manual (1969 650cc Twins) Section B4: Strip/Reassemble Rocker Boxes

WWW icon " Pushrod alignment"

I label the pushrods with a marker when I remove them & replace in their same position. If I remember, else not. As I replace the pushrods I examine them and, ideally, make note of anything special, such as wear to the cups.

  1. With a good dab of grease filling the bottom pushrod cups, lower the pushrods down the pushrod tubes until you feel them contact their respective tappet. When properly seated, the tappets 'stick' in the greased pushrod cups and you can feel the tappets being pulled and pushed up and down by the pushrod.
  2. Without lifting the pushrods off their tappets, fit the rocker box gasket holes over the pushrods, line up all the gasket bolt holes, and press the greased gasket flat.
  3. Last year I used the Covseals 'dry'. Removal this winter was arduous. This year I greased both sides, let them sit an hour, and wiped off excess before putting them on with a couple extra small grease dabs to hold things in place while installing the rocker box.
  4. Double-check the pushrods for engagement with the tappets and have the pushrods standing straight, and parallel with each other.
  5. Before installing the rocker boxes, give a few squirts of oil to moving parts.
  6. Introduce the rocker box from the middle, and, looking up from below, manoeuvre it into place without touching the pushrods. When the three studs are lined up on their holes, gently let the rocker box down onto them.
  7. Fit the two large engine bolts first. They won't quite clear the frame so put the washer on the hole and then insert the bolt through it until the nut just touches the frame on one of its flats. With both hands on the rocker box, gently rock it side to side, barely lifting it, and the bolt will drop down past the frame with a snappy retort.
  8. Finger-tighten the head bolts loosely, and then put the three nuts/washers on the studs before finger-tightening the small rocker box bolts.
  9. I go back and forth between the head bolts (70-1596, BS 3/8-26TPI X 5 7/8 U.H. Tool-3/8BS-5/16W Torque: 18 LBS), rocker box bolts (21-1875, UNC 1/4-20TPI X 2 5/32 U.H. Tool-3/16W Torque: 5 LBS), and rocker box stud nuts (82-0879 BS 1/4-26TPI Torque 5 LBS). I tighten gently, then loosen, then tighten a little more then loosen a little, etc, until all the nuts and bolts are snug and evenly tightened.

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Lightweight Pushrods & Rocker Box Gasket Modification

When I tried using lightweight pushrods it was necessary to modify the rocker box gaskets to accommodate their larger diameter. After modification the gaskets no longer served to guide the pushrods to the rockers when fitting the rocker boxes, so I made a template to guide the pushrods, split it in two, taped it back together for assembly, and removed in two pieces when the rods were placed.

Photo of Triumph pushrod installation

Replacing Rocker Oil Feed Pipe

CompatiblityThe banjo fittings on the rocker oil feed pipe connect to the rocker spindles with domed nuts. Prior to 1973 the domed nuts were 3/8-26TPI, but they were changed to 24TPI UNF in 1973. If you're having trouble threading on replacement domed nuts, suspect a thread mismatch between the nuts and the spindles.

The WS Manual gives a torque spec of 22 lbs for these nuts, but see below.

Always anneal the four copper washers before replacing them, even if you seal them:

Tip! A recipe for a non-leaking rocker oil feed pipe from the TRV7R - Man with the touch, on

"I don't go 22 lb on torque on these. It just seems too tight. I do it by feel. I've had practice though." "Not a bad plan to put some sealant on washers also. Loctite 518 is my sealant of choice, however Hylomar universal blue or any of that family of Hylomar will work good also. Put a thin smear both sides. Wipe hole of washer clean. Hang washer on wire 10 min to flash of solvents in sealer. Handle washer from outside. Assemble & tighten acorn nut. Make sure you don't smear sealant on threads or shaft sliding washer on. Clean box surface, banjo sides, nut face well & dry. Sealant doesn't stick well on oily surface. Wipe off excess quickly."

"If banjo fittings want to spin when tightening nuts, counter hold them on the flats. Don't let them spin & bend tube."

Replacing Engine Torque Stays


Parts iconFig.14 Engine Torque Stays

Photo icon Engine Torque Stay Fasteners.

WWW icon StuartMac on assembling the engine torque stays

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Parts iconFig.5 Valves

WWW icon Vintage Bike Magazine John Healy: "Where is your valve seat?"

WWW icon "Oversized valves fix deep seats?" A very educational thread!

Video icon YouTube  Lunmad: Valve Clearance Adjustment

Note that in the video above, Lunmad uses a slightly unorthodox method to open valves for adjustment.

For example, instead of, as per the WS Manual, opening the DS exhaust valve (pushrod up, rocker down) to adjust the TS exhaust valve clearance, Lunmad closes the TS intake valve.

Tip! Lunmad's method may be the only way to adjust the TS exhaust valve clearance without removing the gas tank.

Replacing Valves in Head


Icon for manual Workshop Manual (1969 650cc Twins) Section B15: Remove/Replace Valves

Icon for manual Workshop Manual (1969 650cc Twins) Section B16: Renewing Valve Guides

Icon for manual Workshop Manual (1969 650cc Twins) Section B17: Decarbonizing

Icon for manual Workshop Manual (1969 650cc Twins) Section B18: Reseating the Valves

Illustration of Triumph valves, valve springs, and collets

Install valves, springs, and retainers as per figure at right. Use red valve spring compressor and grease the split collets to help hold the first in place while inserting the second one.

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Adjusting Valve/Rocker Clearance


Icon for manual Workshop Manual (1969 650cc Twins) Section B5: Adjusting the Valve Rocker Clearances

Looking at the valve clearance specs for the T120 and for the T140 it may appear as though there is an error, but that is not the case. What accounts for the difference? According to Mr. Pete, "Different cams, with different ramps. No quietening ramp at all on the 3134 cam in the T120."

Valve Clearances
Inlet Exhaust
T120 0.002 0.004
T140 0.008 0.006

Mr. Pete also made these interesting comments regarding valve clearance:

And these:

So, when adjusting valve clearances it's better to have a wee bit too much clearance than not quite enough, especially for the exhaust valves, where a lack of clearance may result in the valve burning. On the other hand, too much clearance means the rockers will 'hammer' the valve stem tips.

Note that when a rocker box and/or cylinder head has been removed and replaced, or when the head bolts are re-torqued, it's important to re-check valve clearances after a very brief run-in due to compression of the gaskets. Symptoms of too little exhaust valve clearance include high engine temperature, loss of engine power, and low compression due to the exhaust valves remaining slightly open.

Sound can be a useful guide to setting valve rocker clearance (see 'Adjustment by sound and feel', just below), as well as when evaluating correctness of settings with the engine running.

It's much easier to adjust valve clearance while the carburettors are removed, but adjustment can also be done with just the gas tank and air filters off. And by the way, if you got carried away tightening the valve inspection caps the last time and are having trouble getting them off, gently heating the rocker box cover around them will make them loosen right up.

Valve adjustment tools

The stock Triumph adjustment pins have square heads which make adjustment quite vague. If you're using the square-headed adjustment pins you may want to check out the two-piece valve adjuster tools that are available. In theory these should make adjustment a snap because they allow you to control adjustment with thumb and finger while simultaneously tightening or loosening the locking nut. In practice, the fit between the adjustor and the square pin is too sloppy to give good control.

I find the readily available adjustment pins with hex heads are a big improvement as they make it easier and more accurate to gauge the degree of change in adjustment. With these pins you get good control with an allen head wrench handle as you tighten or loosen the adjuster pin locknut with a short 7/16" box-end wrench.

Coarse adjustment by position

Valve clearances should be set to .004" for exhaust and .002" for the intakes. A common method of obtaining 'ballpark' settings is to run the adjustors in until they just contact the valve stems by feel, and then back them off 1/8 of a turn for exhaust, and 1/16 turn for intake.

Adjustment by sound and feel

Another common adjustment method is to grasp the rockers with thumb and index finger and rock them up and down:

Positioning Valves for Clearance Adjustment

In order to adjust a valve's clearance, the valve must be closed. To position a valve in its closed position (rocker up), make the opposite valve fully open (rocker down).


Formally, I had difficulty getting consistent valve clearance measurements, probably due to inaccurate positioning of the valves. I've improved this in two ways: using the rear wheel instead of the kickstart lever to do the fine positioning, and by using a finger to gauge when a rocker has reached to lower limit of its travel.

So, to adjust the DS exhaust valve, make it closed by opening the TS exhaust valve as follows:

  1. Place fingertip on TOP of the adjuster screw of the TS exhaust valve rocker

    Traps!Do NOT place finger anywhere but on TOP of the rocker - getting a finger caught between the rocker and the rocker box would be like having it in a guillotine!

  2. Put the bike in second gear and rotate the rear wheel forward, making the TS rocker move downwards
  3. Continue rotating the rear wheel forward until the TS rocker just begins to rise again
  4. Now rock the rear wheel back and forth until the TS rocker is positioned all the way down
  5. The TS valve is now open and the DS valve is fully closed and ready for adjustment

On adjusting the clearances:

Adjustment after Re-torquing

When the cylinder head has been removed and replaced, valve clearance needs to be re-adjusted several times due to gasket 'crush'. Adjust:

  1. After running the engine stationary for several minutes in shop
  2. Again after a short ride
  3. Again after re-torquing the head bolts

Finally, pro mechanic TR7RVMan points out something that can go wrong while adjusting valve clearance. Removing the spark plugs can cause a fragment of carbon to break off the plug threads and get trapped in the valve seat, holding the valve open slightly. After adjustment is made, starting the engine blows out the carbon leaving no clearance. Don says Triumphs are not terribly prone to this, but it can happen. To avoid the possiblity he says leave the plugs in, or start and blip the engine after loosening the plugs one turn and then remove them. Of course the engine has to cool before adjustment is made.

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Engine Compression


Video icon YouTube Lunmad: Compression Test

Compression Test

Testing engine compression is a quick and easy way to determine an engine's general health with regards to valves, rings, and cylinders.

Five easy steps:

If compression is low, add small amount of oil to the cylinders and retest.

If valves are suspected, check to ensure there is adequate valve clearance to prevent valves from closing fully.

Sudden Loss of Compression


WWW icon "1969 T120R magically loses compression"

A sudden loss of engine compression can result from gas washing the pistons.

Once, after sitting unused (very rare) for ten days, the Bonnie seemed to give up all compression after the first kick. TR7RVMan on correctly diagnosed the problem and offered a solution which consisted of pouring a couple of tablespoons of oil down the plug holes, kicking over the engine several times with the plugs out to remove excess oil, replacing the plugs, and starting as usual. The method worked perfectly and normal compression was restored as soon as the bike started.

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Ignition Timing


WWW icon Hermit's Illustrated Ignition Timing with Points Complete instructions for static and dynamic timing using points.

Manual icon Workshop Manual (1969 650cc Twins) Section B28: Removing & Replacing the Contact Breaker

Manual icon Workshop Manual (1969 650cc Twins) Section B29: Ignition Timing - Initial Procedure

Manual icon Workshop Manual (1969 650cc Twins) Section B30: Static Timing Where No Stroboscope is Available

Manual icon Workshop Manual (1969 650cc Twins) Section B31: Ignition Timing by Stroboscope

Video icon Lunmad: Ignition Timing

Note that the timing mark on Lunmad's 650 rotor corresponds to TDC. On Bonnie the timing mark corresponds to 38 degrees BTDC. As mentioned by Lunmad in the comments section, use the flywheel locator tool to determine which location the timing mark on your bike's rotor represents.

Setting Ignition Timing with Points


WWW icon Hermit's Illustrated Ignition Timing with Points Complete instructions for static and dynamic timing using points.

WWW icon TR7RVMan: Ignition Timing w. Points Don details many finer points about setting up points... Definitely a must read!

WWW icon "Anyone still running points ignition?" Lots of love for points here, but only a couple of good pointers.

The contact breaker points gap for late-60s 650 Triumphs is .014-.015-.016".

For clearly illustrated instructions on setting ignition timing with points see "Hermit's Illustrated Ignition Timing with Points". Also be sure to read TR&RVMan's superb post on points ignition timing.

Determining When Points Open

Setting points accurately requires knowing exactly when the points open - that's when the coil produces a spark. There are many ways to achieve this, including:

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Setting Ignition Timing with Pazon


Manual icon Pazon installation, timing, and trouble-shooting

Photo showing Pazon electronic ignition installation

Static Timing

Use a flywheel locator tool (OR timing pointer and rotor timing mark if the one on your rotor points to 38 degrees BTDC and not TDC) to locate 38 deg advance.

Dynamic Timing

Use strobe on either cylinder for dynamic timing

It would probably be helpful to establish corresponding reference marks on the Pazon disk and the timing cover.

Primary Cover Timing Pointer

The timing pointer in the primary chaincase cover on later model 650s is basically a short nail - a flat head on one end a pointer on the other. It is a press fit in the primary cover.

Traps!If you need to remove or replace the pointer you can drive it out from the inside, but be sure to back up the cover and use great care to avoid cracking the primary chaincase cover.

Replacing rotor cover after timing

If the cover is installed on the chaincase before screws are inserted, mating the first screw to the threads in chaincase can be annoying. Easier to find the hole by inserting the top screw in the cover and fitting both together dangling from a Phillips screwdriver.

Removing magnetic rotor center

Use Metric M8 bolt threaded into rotor.

Spark Plugs


Icon for manual Workshop Manual (1969 650cc Twins) Section H3: Sparking Plugs

Manual iconTriumph Service Bulletin #12-68 "Spark Plug Cross Reference Chart"

WWW icon NGK-spark plugs.jpg Trouble-shooting Dry & Wet Fouling of Spark Plugs

WWW icon How to Read Your Spark Plugs

Used NGK for quite a while, but have returned to using Champion N3C (new Champion designation 801).

Plug gap: .025". Chart showing NGK sparkplug heat ranges

Interpreting NGK plug designations:
B= 14mm plug thread
7 = Temperature range
E = 19mm plug thread reach
S = Standard super copper core electrode

The higher the NGK number, the colder the plug
The lower the Champion number, the colder the plug

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The Exhaust System


Icon for manual Workshop Manual (1969 650cc Twins) Section B13: Removing and Replacing the Exhaust System

Parts iconFig.15 Exhaust System

WWW icon "Exhaust Leak?" Sealing the exhaust pipe crossover

Removing Exhaust System

If you don't have a crossover pipe and you don't fit the muffler strap, you can remove the exhaust pipes and mufflers as a unit: remove or loosen the exhaust pipe clamps (7/16"), the exhaust pipe engine bracket (Phillips screws and 7/16" nuts), and the muffler hanger bracket nuts/bolts (1/2").

The nuts holding the chrome exhaust brackets to the engine are 5/16" BS, but it's not necessary to remove them.

When removing and replacing the exhaust pipes on the exhaust pipe adaptors, I find it's ok to hit them with a plastic mallet using a thick, folded rag as padding.

Sealing Exhaust Leaks

I have Bonnie's original headers with crossover pipe in inventory, but I replaced them (several times - I've seen the gravel and the damage done) with separated headers.

Not running headers with a crossover, I don't have the problem of sealing exhaust leaks there, but apparently this can be a problem, especially with reproduction parts. Don's method takes the guesswork out of centering the crossover pipe to cover the slots in the stubs on the headers, this and other good tips. See link above.

Loose Baffles

Loose lips sink ships and loose baffles rattle. A loose baffle can be re-welded, but it requires drilling an access hole on the inside of the muffler where the baffle begins or ends, depending upon which end is rattling. A fter welding the baffle they welded the hole shut - No rattle, no visible repair.

Mike James once suggested that the cause of that loose baffle might have been the fact that I don't install the muffler brace ((70-5676, Ref.27 Fig.15 Page 41 #7). He makes an excellent point, but I wonder how many people actually fit this part?

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The Transmission


Icon for manual Workshop Manual (1969 650cc Twins) Section C: Transmission (TOC)

manual icon Triumph Overhaul Manual Transmission, Remove & Inspect

manual icon Triumph Overhaul Manual Transmission Assembly

Parts iconClutch, figure and part listing

Parts iconPrimary Chaincase, figure and part listing

WWW icon 'Unit 650 clutch thrust washer' Clutch thrust washer discussion, inc. types & changes in size.

WWW icon TR7RVman's clutch tips Restoring & maintaining the Triumph clutch.

Primary Chaincase

The primary chaincase houses the transmission, which consists of the engine sprocket, the primary chain, and the clutch assembly. The transmission's job is to transfer energy from the engine sprocket to the gearbox mainshaft, the gear cluster, and subsequently to the gearbox sprocket and rear wheel.

Primary Chaincase Lubrication

See Lubrication Schedule, Primary Chaincase

Primary Chaincase Cover and Gasket


WWW icon 'Primary Case removal'

If you're having difficulty removing the chaincase cover, or keeping the gasket in place while putting it back on, have a look at the thread above.

Tip! If your primary chaincase cover is good and flat, try this gasket tip: put gasket sealant on the side of the gasket that goes to the cover and grease the side that goes to the chaincase. The next time you remove the cover the gasket will stay on the cover and you can probably re-use it upon re-assembly.

Checking Primary Chain Wear & Adjusting Chain Tension


Icon for manual Workshop Manual (1969 650cc Twins) Section C2: Adjusting the Primary Chain

www icon Side-by-Side photos illustrating Primary Chain Wear When adjusting 'slipper' becomes too arched replace the chain.

www icon Primary Chain adjuster This thread relates to a T140, but includes a lot of info that also pertains to the 650s as well.

Checking Primary Chain for Wear

The WS Manual method to check wear in a primary chain:

Checking Primary Chain Tension

Excessive tightness of the primary chain can damage the DS crankshaft bearing, the chain tension slipper, clutch components, and/or the gearbox mainshaft and its bearing. Conversely, too much slack can give rise to some bad-assed noises from the primary chaincase, not to mention damage to the stator or the primary case itself due to rubbing.

The WS Manual specifies 1/2" total up-and-down slack in one place, and 3/8" in another. Although this ambiguity is often regarded as an error, it might also be interpreted to mean that the correct adjustment may vary. Like drive chains, primary chains will vary in tension from one position of the chain to another. Therefore, rotate the chain and check tension in multiple positions until you find the points of greatest and least slack.

Adjusting Primary Chain Tension

In order to adjust the primary chain tension, the oil must be drained from the primary chaincase, so it's only logical to check the tension at each oil change and adjust if necessary.

  1. Drain the primary chaincase oil..
  2. When oil has finished draining, insert Tool iconPrimary chain tension adjuster D2108 into the drain hole.
  3. Hold engine against compression with kickstart lever (Manual iconService bulletin 1-69, January 27, 1969)
  4. Use a screwdriver to turn the adjustor tool in to tighten, out to loosen
  5. Through the inspection cap on top of the chaincase, move chain up and down with finger or wire and adjust total up and down free play to 3/8" - 1/2".

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Dismantling the Transmission


Icon for manual Workshop Manual (1969 650cc Twins) Section C3: Removing and Replacing the Primary Cover

Icon for manual Workshop Manual (1969 650cc Twins) Section C4: Removing and Refitting the Clutch Plates

Icon for manual Workshop Manual (1969 650cc Twins) Section C5: Inspecting the Clutch Plates and Springs

Icon for manual Workshop Manual (1969 650cc Twins) Section C8: Removing & Replacing the Stator & Rotor

Icon for manual Workshop Manual (1969 650cc Twins) Section C9: Removing & Replacing the Clutch & Engine Sprockets

The clutch assembly, engine sprocket, and primary chain are removed simultaneously as one after slacking the chain and removing the stator and rotor.

Exploded figures with parts numbers and specs:

Step-by_Step Procedure

  1. Drain chaincase oil and slacken primary chain Tool icon Primary chain tension adjuster D2108
  2. Slack off the left side foot peg (3/4" box end) and rear brake adjustor
  3. Remove cover screws using your Posidrive screwdriver and a 1/2 wrench for the domed stator stud nuts 21-0544 (3)
  4. Remove chaincase cover
  5. Remove 70-4565 rotor nut with 9/16BS wrench or socket
  6. Remove 14-0702 locking nuts (3) from stator studs (13mm deep socket is a perfect fit)
  7. Free alternator wires and remove stator
  8. Remove Rotor Tool icon Wheel Puller
  9. (Store rotor AWAY from metal/magnets)
  10. Loosen engine sprocket (Tool icon Engine Sprocket Puller)
  11. (Remove 14-0403 locking nut (9/16) and adjusting pin from pressure plate)
  12. Remove 57-2526 clutch pressure plate adjustment nuts (3) using Tool icon clutch pressure plate spring adjustment tool
    Bit of a PITA due to 'pips' under heads - WS Manual says 'Put a knife under head of nut to facilitate removal' - never works for me until they're already part way out
  13. Remove Pressure Plate
  14. Using a hook for friction plates and a magnet for steel plates, remove clutch plates and carefully stack in same order they were installed.
  15. Remove 21-0586 (self-locking) clutch nut using Tool icon clutch locking tool & a 7/8 socket and breaker bar.
    If difficult to remove, use air wrench
  16. Loosen clutch center from mainshaft.

The clutch center makes a tapered fit to the mainshaft and therefor can and should be a very tight fit. Removal is accomplished using a Tool icon clutch center extractor tool.

Traps!Important to realize the clutch center extractor is an extractor and not a puller. The extractor's outer threads do not deeply engage those of the clutch center. It's not meant to be forcefully tightened against the mainshaft until the clutch center and mainshaft separate. Using it that way just results in stripping the extractor body's outside threads. (Ask me how I know).

Used correctly, the extractor bolt is only tightened enough to pre-load an outward stress between the clutch center and the shaft. Then, the extractor bolt is struck by light to medium blows from (ideally) a brass hammer. Under normal circumstances this works.

In stubborn cases, using an impact driver at its lowest setting on the extractor bolt will probably do the trick. When all else had failed, that method succeeded in removing a clutch center which had Photo icon sheared the key and spun on the mainshaft.

  1. Remove clutch center, chain wheel, primary chain, and engine sprocket all together
  2. Remove half-moon key from mainshaft

Tip!Use end cutters to remove stuck keys from a shaft WWW icon TR7RVMan on

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Inspecting Transmission Components


Icon for manual Workshop Manual (1969 650cc Twins) Section C10: Inspection of the Transmission Components

Icon for manual Workshop Manual (1969 650cc Twins) Section C5: Inspecting the Clutch Plates and Springs

Clutch Pack Thickness

TR7RVMan states that a genuine Triumph clutch stack will measure 'very close' to 1.400", while an Aerco 7 plate clutch with all new steels will measure 1.380".

Clutch Center

Shock Absorber Rubbers


Icon for manual Workshop Manual (1969 650cc Twins) Section C7: Renewing Shock Absorber Rubbers

Video icon YouTube Lunmad "Fitting cush-drive rubbers Triumph Bonneville T120R"

Video icon YouTube Raber's Tech Tips, Episode #4 "Triumph Unit Construction Twins Cush Rubber Installation"

Clutch Center & Thrust Washer Compatibility


WWW icon John Healy: Thrust washer/clutch center compatibility

WWW icon 'Unit 650 clutch thrust washer' Thrust washers, discussion of types & changes to size

Photo icon Early and late clutch centers/thrust washers

Triumph 650s used the 57-1734 clutch hub from 1963-69. It matches up with the 57-1735 thrust washer. These parts were superceded by clutch hub 57-3929 and thrust washer (57-3931) in 1970.

CompatiblityThese parts are not mix-and-match as the inner diameter of the thrust washers are different.

It's easy to tell if a thrust washer is made for a particular clutch hub - the ID of the thrust washer should fit the matching recess in the hub.

Both thrust washers (57-1735 and 57-3931) are, or were, available in different materials:


For thrust washers with one side copper and one side steel, place the copper side towards the clutch basket.

The spec given by the manual for thrust washer thickness is .052/.054". Some vendors supply thicker washers, but there are reports that too-thick a washer can cause the clutch pack to lock up when the clutch center locking nut is tightened.

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Reassembling the Transmission


Icon for manual Workshop Manual (1969 650cc Twins) Section C9: Removing & Replacing the Clutch & Engine Sprockets

Icon for manual Workshop Manual (1969 650cc Twins) Section C8: Removing & Replacing the Stator & Rotor

Icon for manual Workshop Manual (1969 650cc Twins) Section C4: Removing and Refitting the Clutch Plates

Icon for manual Workshop Manual (1969 650cc Twins) Section C3: Removing and Replacing the Primary Cover

Reassemble the Clutch Center

  1. Lay the clutch center flat
  2. Slather it with grease to hold the rollers in place during assembly

    Traps!On later models sharing oil between primary chaincase and crankcase, avoid wheel grease as it contains fibers that could harm the shell bearings - use lithium grease instead

  3. Position the 20 rollers
  4. Put on the thrust washer, copper/brass side up (out, to clutch plates)
  5. Place the duplex sprocket over the clutch center
  6. Put on the clutch hub assembly (shock absorbers, plates, spider) inside the sprocket
  7. Give a few taps with plastic mallet to seat everything

Reinstalling Engine Sprocket & Clutch Assembly

If you're installing the DS crankshaft oil seal now, be sure to see the DS Crankshaft Oil Seal section.

See Sprocket Alignment note just below.

  1. Install moon-shaped key to mainshaft, well-greased
  2. Position mainshaft with the key at 12 o'clock
  3. Place chain over engine sprocket (long shoulder to oil seal and bearing) and duplex sprocket
  4. Arrange the sprocket(s) so the keyway in the clutch center is at 12 o'clock
  5. Offer the engine sprocket and clutch assembly simultaneously to their respective shafts, keeping their keyways aligned with the keys on their respective shafts

    Tip!Getting the clutch center over the key can be a real pain! It helps to tip the duplex sprocket and clutch assembly slightly forward and eyeball down the clutch assembly's keyway. Kevin paints the key bright yellow and runs a trace line down the shaft. Pointing a flashlight down the keyway he can see the yellow key for alignment.

  6. Tap with plastic mallet if necessary
  7. Install self-locking clutch nut and thick washer to end of mainshaft

    The clutch nut is one of the four places to use Loctite on a Triumph

  8. Use deep-well socket and plastic mallet to seat the engine sprocket
  9. Torque clutch nut to 50lbs
  10. Check whether the engine and duplex sprockets are aligned using a Photo icon steel straight edge placed across the engine sprocket boss to see if it aligns with the duplex sprocket boss

    If the sprockets are not perfectly aligned, use shims (70-8038 .010", 70-8039 .015", 71-2660 .030") behind the engine sprocket to align it to the duplex wheel

  11. DO NOT install clutch plates & pressure plate yet

    You'll need to use the clutch locking tool in order to accurately torque the rotor nut (below)

  12. Install distance piece over crankshaft, chamfer towards sprocket
  13. Install 71-0082 woodruff key and rotor
  14. Install 70-3975 tab washer and 70-3977 shouldered rotor nut

    Exploded view of Triumph main bearing, engine sprocket, and rotor in primary chain case

  15. Torque the rotor nut to 30lbs - the rotor nut is another one of the four places on a Triumph to use blue Loctite

    Tip! When torquing the rotor nut, be sure to hold the crankshaft using clutch locking plates and not the rear brake and 4th gear. The latter cause part of the applied torque to be absorbed by the clutch shock absorber rubbers, making the torque reading inaccurate (John Healy,

  16. Now install clutch plates and pressure plate and adjust pressure plate for trueness (below)

    Compatability If you're working on a pre-unit model both the first and last clutch plates are steel, while on unit model clutches the first plate installed is friction and the last plate is steel.

  17. When replacing stator, torque the three nuts securing it to 20lb - no Loctite required

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Adjusting the Pressure Plate


Manual icon Workshop Manual (1969 650cc Twins) Section C6: Adjusting Clutch Pressure Plate

WWW iconTriumphRat Forum Clutch pressure plate adjustment: Peg's method

WWW Triumph Forum Don's take on pressure plate adjustment

Three adjustors permit adjustment of the pressure plate until it lifts and falls evenly and compresses the clutch plates evenly all around.

After initially setting the adjuster nuts flush with the ends of the adjuster screws, use a pressure plate spring adjustment tool to adjust the three pressure plate spring adjustment nuts to eliminate wobble of the pressure plate as it turns.

To check for wobble, pull in the clutch lever to raise the pressure plate and then turn the clutch using the kickstarter. Observe the outside edge of the pressure plate for wobble as it goes around and use the spring adjustors to compensate for unevenness.

Tip! You can also screw in the clutch rod pin adjuster to hold up the pressure plate for wobble adjustments - another great idea from Peg!.

Wobble can be gauged by eye, but a pointer is a great help and can be as simple as a piece of coat hanger wire and some duct tape.

After adjustment, make final check is to see that the pressure plate lifts evenly all around when pulling in the clutch lever.

Properly adjusted, clutch spring tension should be a happy medium between too loose (clutch will slip) and too tight (excessive hand pressure required to operate the clutch and possibility of damage to the clutch rod). If the coils become bound or the spring tension otherwise too high, loosen the three adjustors by small, equal amounts at a time until spring tension is eased and then re-check wobble.

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Adjusting the Clutch Operating Mechanism & Clutch Cable


Manual icon Workshop Manual (1969 650cc Twins) Section C1: Adjusting the Clutch Operating Mechanism & Cable

Video icon YouTube Raber's Tech Tips, Episode #1 - Triumph Unit Twin Clutch Pushrod Adjustment

The Rabers' video well demonstrates the standard WS method:

  1. Make cable entirely slack using the handlebar clutch cable adjustment
  2. Remove vertical inspection cap from primary chaincase cover
  3. Inside, slack off the clutch rod adjuster screw's locking nut, making sure the nut is backed off well
  4. With screwdriver, slack the adjuster screw and then carefully tighten it until the pressure plate just begins lifting
  5. At this point, double-check to see that the cable is still slack
  6. From the point of contact between the adjustor screw and the clutch rod, back off the adjuster screw to
    provide necessary clearance:
  7. Lock the adjuster screw with the lock nut
  8. Finish by adjusting the cable at the handlebars - leave at least 1/8" of free-play in the cable

Adjustment Tips & Techniques

The procedure is pretty straight forward, but there are a couple of tips and techniques for best results.

Tip!To begin with, it's essential that the clutch cable is completely slack before beginning the adjustment. If not, there's a good chance the 3-ball clutch operating mechanism in the outer gearbox cover will wind up out of its adjustment range - see "Clutch Operating Mechanism Pops or Clicks" just below under "Clutch Problems".

Tip!Stuart gives us a technique to determine exactly when the clutch rod adjustment screw contacts the clutch rod. He uses just a thumb and a finger to lightly hold the screwdriver as he turns the screw in. When the screw and the rod meet the screwdriver will stop.

Tip!Guys use different methods to hold the adjustment screw stationary while the lock nut is tightened: many use a screwdriver through a socket and tighten the nut using vice grips on the socket (but be kind to your sockets and use a rag). Those who have one use a special offset hollow-head socket wrench through which they can insert a screwdriver. DMadigan has a very simple and clever method: he simply pulls in the clutch lever to load the screw with tension while he tightens the nut!

Tip!Whichever method you use, eyeball the adjuster screw head position before and after tightening down the locknut to be sure it didn't move.

Tip!As pointed out by TR7RVMan, new clutch plates will decrease in thickness as they 'bed down', and as the thickness of the clutch pack decreases so does the clutch rod clearance. When the clutch rod clearance becomes less than zero, clutch plates get held apart resulting in the clutch slipping and possibly burning out. So, when adjusting a clutch with new plates, provide slightly additional clearance - something between 3/4 turn and the WSM full turn, and then be sure to check the adjustment regularly until the plates are broken in.

Clutch Operating Mechanism (Ball & Ramp)


Icon for manual Workshop Manual (1969 650cc Twins) Section D7: Clutch Operating Mechanism

Parts icon Fig.9 Gearbox outer cover (Showing ball & ramp parts)

See Clutch Problems, '.. Pops or Clicks' immediately below.

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Clutch Problems

Clutch Operating Mechanism Pops or Clicks

If a popping or clicking noise occurs when pulling in the clutch lever it means the 3-ball clutch operating mechanism in the outer gearbox cover is out of its adjustment range. This occurs if the clutch rod is under-adjusted (too much slack) and the cable adjustment is over-adjusted in compensation. That combination of poor adjustment advances the static position of the clutch operating mechanism until normal operation of the clutch lever/cable forces the mechanism past its designed operating range. When that happens the steel balls click and pop as they pass the ends of their ramps.

All that's necessary to correct the condition is to properly adjust the clutch operating rod and the clutch cable as described above.

Clutch Drags & Neutral Hard to Get

Possible causes:

Clutch Pull Very Stiff

Kickstart Lever Won't Turn Engine/Gearbox Won't Engage with Engine

Gears Crunch When Selecting First from Neutral

It's been said that the crunching sound made when selecting first gear from neutral has a Triumph part number. Not quite, but it is very common. Usually the problem is clutch, not gearbox. Some common causes of 'the crunch' and ways of reducing it:


Techniques for Reducing the "Crunch"

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The Gearbox


Icon for manual Workshop Manual (1969 650cc Twins) Section D: Gearbox (TOC)

manual icon Triumph Overhaul Manual Gearbox, Remove & Inspect

manual icon Triumph Overhaul Manual Gearbox Assembly

Parts icon Fig.9 Gearbox outer cover  /  Fig.7 Gearbox inner cover  /  Fig.8 Gearbox, gears and shafts

Tool icon Triumph Service Bulletin #329 "Third gear ratio and selector forks modifications"

WWW icon Links John Healy on 4 and 5-speed Triumph gearboxes including leaf-springs versus plungers

WWW icon Kevin Roberts' "Upgrading a 5-speed gearbox" Includes excellent photos and informed discussion of Triumph gearboxes.

Compatiblity "The Spring Report" In his deep dive into Triumph unit 650 gearbox components, Mike James provides completely new perspectives on gearbox plunger springs and runs down the raft of changes to springs, plungers, plunger holders, and gearshift camplates from 1968 to 1970. A must-read. (PDF, 8.5mb)

Video icon YouTube - Rebuilding the T160 Gearbox Nicely shot and narrated 5-speed assembly.

Hermit's Gearbox Articles, Illustrations, Photos & Animations


WWW icon Index to all of Hermit's Illustrated Gearbox Articles

Photo icon Stills, Rear View

Video icon Gear Animation, Rear View (wait for it)

Photo icon Stills, Front View

Photo icon Gearshift lever & gear shift quadrant deflection from center

Video icon Gear Animation, Front View (wait for it)

Gearbox Lubrication

See Lubrication Schedule

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Gearbox Problems


Manual icon Triumph Service Bulletin #329 "Third gear ratio and selector forks modifications"

Manual icon Triumph Service Bulletin #8-59 "1969 650s jumping out of 2nd/3rd gears"

Manual icon Triumph Service Bulletin Trouble-shooting excerpt: "Improper Upshift, Third Gear"

WWW icon "Gear selection malfunctions after gearbox overhaul" The thread I started on Bonnie's shifting problem

WWW icon "69 Bonneville jumping out of gear"

WWW icon "T120 unit gearbox problem"

WWW icon "Gear Lever movement" Faulty gear selection thread

WWW icon "Gear shifter hangs up when down shifting" Don gives us good advice on diagnosing gearbox problems

WWW icon John Healy: 4/5-speed gearbox conversion Inc. photos comparing 4- & 5-speed components

Video icon YouTube Lunmad: Gearbox Video

Jumping out of Gear

The problem of jumping out of 1st gear plagued Bonnie for over two years. Eventually I came to view the problem as being with down-shifting more than popping out of gear. That's when I began to suspect the gear change quadrant.

When I finally replaced the gear change quadrant in June of 2016, it fixed the problem straight away. The old gear change quadrant hadn't traveled far enough when down-shifting, leaving 1st (and sometimes 2nd and 3rd) gears selected incompletely. The downshift travel of the new unit from Baxter traveled about 3/32" further than the original.

With the new gear change quadrant installed in the outer cover, I fitted a degree wheel to it to observe how far the gear change quadrant deflected from center when the gearshift lever was moved to the up and down-shifting positions. The up and down-shift deflections were nearly identical: 19 degrees for upshift, and 19-1/2 degrees for downshift.

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Outer Gearbox Cover


Parts iconFig.9 Gearbox outer cover

Some say an outer gearbox cover gasket can cure certain gearbox problems, but it did nothing for Bonnie. Since fixing Bonnie's gearbox I've used no gasket because she didn't come with one and it's not necessary for sealing - Hylomar or other sealant will take care of that.

Kickstart Lever Tapered Pin


WWW icon "Stuck kickstart pin"

Removing the tapered pin holding the kickstart lever in place is not always so easy. The pin gets bent out of shape by the force of repeated kickstarts, effectively jamming itself in the bore. It sometimes helps to jam the kickstart lever forward using a plastic mallet and then whack the pin smartly against the nut threaded flush.

As noted in the thread above, some kickstart pins are made of harder material than others and they tend to distort less than softer ones.

Traps!When replacing the tapered pin, be sure to introduce it from the rear with the kickstart lever in the upright position. Installed with the nut at the rear, the pin fouls the footrest.

Removing Outer Gearbox Cover


Icon for manual Workshop Manual (1969 650cc Twins) Section D2: Removing & Replacing the Outer Gearbox Cover Assy

  1. Off the pipes/mufflers
  2. Off engine mounting plate (or footrest)
  3. Slack clutch cable, remove from hand lever, then gearbox
  4. Engage 4th gear (for loosening/tightening nuts later)
  5. Remove case screws and domed nuts
  6. Depress kickstarter lever slightly - to allow kickstart quadrant to clear inside top of gearbox
  7. Tap cover w. plastic mallet until free
  8. WSMan: "Gear change pedal should be carefully raised then depressed, to control the release of the plungers and springs from the gear change quadrant"

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Dismantling and Reassembling the Gearchange Mechanism


Icon for manual Workshop Manual (1969 650cc Twins) Section D4: Dismantling & Reassembling the Gear change Mechanism

Parts iconFig.9, Gearbox outer cover (Showing gearchange mechanism

Tip!If the quadrant return springs (57-0404) need replacing, TR7RVMan suggests using T140 springs (57-7051), which are stiffer. They center the gearshift lever better for more positive shifts and ease in finding neutral.

Kickstart Mechanism


manual icon Workshop Manual (1969 650cc Twins) Sections D3: Dismantling & Reassembling the Kickstart Mechanism

manual icon Workshop Manual (1969 650cc Twins) Sections D5: Inspecting the Gear change & Kickstart Components

manual icon Workshop Manual (1969 650cc Twins) Sections D6: Renewing Kickstart & Gear change Spindle Bushes

Photo icon Kickstarter parts Photos of 1969 T120R Kickstart parts showing part numbers and assembly order

Parts iconFig. 8, Gearbox shafts and gears (Showing kickstart mechanism)

Now pay attention because there will be a quiz later: the kickstarter nut at the end of the mainshaft is one of the four places to use Loctite on a Triumph.

Inside the gearbox, the kickstarter shaft rotates a quadrant which engages a pinion gear on the mainshaft. The pinion gear turns freely on the mainshaft, but a small spring permits it to part-time engage a ratchet which is splined to the mainshaft and therefore turns it

On the transmission side, the mainshaft connects, through clutch center and clutch plates, to the duplex sprocket, duplex chain, and engine sprocket on the DS end of the engine's crankshaft.

While the clutch lever is in and clutch plates disengaged, pumping the kickstarter lever is to no avail: the clutch center and the steel plates turn, but rotation ends there due to lack of engagement with the friction plates. This action, "freeing the clutch", is performed at the beginning of each riding day as a way to break the "stiction" between the steel plates and the friction plates.

However, supposing the engine doesn't turn over when the clutch lever is out and the kickstarter is depressed? Obviously there's a problem, but where? As we just saw, some parts to the kickstart mechanism are in the gearbox and others are in the primary chaincase so there's only a 50/50 chance of finding the problem by randomly removing one of the covers.

Peg to the rescue with this simple diagnostic:

Tip!With the bike on its center stand, engage any gear and depress the kickstarter while holding the rear wheel or applying the rear brake very lightly. If the wheel turns the problem is inside the primary chaincase - most likely a sheared woodruff key fixing the clutch center to the mainshaft. If the wheel doesn't turn, the problem is with the part of the mechanism located inside the gearbox - quadrant, pinion, spring, ratchet, etc.

Replacing Outer Gearbox Cover


Icon for manual Workshop Manual (1969 650cc Twins) Section D2: Removing & Replacing the Outer Gearbox Cover Assy

Photo icon Posidrive screw locations in outer gearbox cover

  1. Apply jointing compound
  2. Turn kickstart pedal halfway down (its operational stroke)
  3. Offer cover to gearbox
  4. Check that kickstarter returns

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Removing Inner Gearbox Cover


Icon for manual Workshop Manual (1969 650cc Twins) Section D8: Dismantling the Gearbox

Parts iconFig.9 Gearbox inner cover

Removing the Inner Cover & Dismantling the Gearbox

  1. Select 4th gear
  2. Remove gearbox outer cover (see above)
  3. Remove right engine plate
  4. Using rear brake, remove nut holding kickstart pinion ratchet
    (If transmission is already dismantled, a Tool icon clutch locking tool will work too)
    Note: alternatively, leave the kickstart nut in place and remove the mainshaft (below) and inner cover as a unit. Then you'll be all ready to reassemble the gearbox using Hugh Hancox's method.
  5. Dismantle transmission, see Dismantling Transmission above
  6. Remove gearbox inner cover
    1. Remove camplate indexing plunger and spring (3/4" socket)
    2. Remove oil lines from oil pipe junction block
    3. Remove junction block bolt (1/2" socket w extension)
    4. Remove bolt 21-1907 (Ref#20 Fig.7 #7) (7/16" socket)
    5. Remove Posidrive screw 14-6608 (Ref#22 Fig.7 Page 25 #7) (Posidrive)
    6. Remove allen head screw 14-7023 (Ref#23 Fig.7 #7 (.2335")
    7. Tap 'ear' w plastic mallet
    8. Withdraw cover slowly, using finger to keep the layshaft from coming out
  7. Remove gear selector fork spindle and then the forks (don't lose the 2 rollers)
  8. Remove main shaft, followed by
  9. layshaft and gears
  10. Thrust washers
  11. Plunger carrier & camplate
  12. Gearbox sprocket nut and sprocket Tool icon (1 11/16" socket)

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Inspecting the Gearbox Components


Icon for manual Workshop Manual (1969 650cc Twins) Section D9: Inspection of the Gearbox Components

Layshaft End Play

Although the manual doesn't give any spec, there seems to be a consensus on that layshaft end play should be around .005". By general agreement, it's not critical as long as there is some.

Two possible methods of gaging end play:

Gearbox Sprocket


Icon for manual Workshop Manual (1969 650cc Twins) Section D12: Changing the Gearbox Sprocket

Fair amount of trouble to replace the gearbox sprocket, so whenever you are already in the neighborhood it pays to give it a good inspection before putting things back together.

Sprocket wear is contagious, so to speak, as is chain wear. Wear on any one component in the final drive will result in increased wear to the others as well. Giving good care to the drive chain (cleaning, lubricating, and properly adjusting) will give the gearbox sprocket much longer life, thereby postponing its vexatious replacement.

1969 T120R Gear Cluster Illustrations

Illustration of Triumph layshaft and mainshaft gear cluster with part numbers and descriptions

Gears, Shafts, Bearings, & Bushes('69 T120R)

Exploded diagram of Triumph gearbox showing descriptions and part number of bearings, bushings, shafts, and gears for a 1969 Triumph T120R 650 motorcycle

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Replacing Gearbox Inner Cover Bearings


Icon for manual Workshop Manual (1969 650cc Twins) Section D10: Renewing Mainshaft & Layshaft Bearings

Drawing and description of replacing the layshaft bearing in the inner cover of a Triumph 650

Replacing Mainshaft Bearing in Inner Gearbox Cover

(Mainshaft ball journal bearing S35-7 - 3/4 x 1 7/8 x 9/16")
  1. Cool the mainshaft bearing
  2. Thoroughly heat inner gearbox cover
  3. Fit the mainshaft bearing (S35-7) (Tool-Z15)

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Removing/Replacing Mainshaft and Layshaft Bearings in Gearbox Casing


Icon for manual Workshop Manual (1969 650cc Twins) Section D10: Renewing Mainshaft & Layshaft Bearings

manual icon Triumph Overhaul Manual Countershaft Sprocket/Mainshaft High Gear Assembly

The gearbox casing holds two bearings:

Removing Mainshaft & Layshaft Bearings from Casing

I've read that these bearings can be difficult to remove, but I've had good luck getting them out.

From the primary chaincase side, I've used a five-inch long 3/8" drive extension to drive out the layshaft closed end needle roller bearing (57-1606). Access to the bottom portion of this bearing is blocked by the primary chaincase, but the extension can reach the bearing's top left, and right hand sides and that has proven sufficient for driving it out.

The mainshaft high gear bearing (50-0448) is driven out from the inside of the gearbox. I've used a 1/2" drive extension and a 1 1/16" deep well socket.

Replacing Mainshaft & Layshaft Bearings in Gearbox Casing

The first two times I replaced gearbox bearings I did it 'Hughie Hancox style': a torch and a hammer with drift. When this method failed the third time, I enlisted the help of a local machinist to press them in using a 50-ton industrial hydraulic press.

In order to press in the DS needle bearing I made a wooden base for engine on the primary side:

Photo icon Engine Base

Replacing High Gear Ball Journal Bearing (57-0448)

When heating up the gearbox casing I use a non-contact infrared thermometer to take the guesswork out of attaining a 200 degree temperature evenly.

Tip!An indispensable trick is to use an old mainshaft as a "stick" to line up the large mainshaft bearing (57-0448) squarely with its housing in the gearbox casing. (Photo icon Photo). Once it was started squarely I used a large, heavy drift against the outer race to drive home the bearing (Photo icon mainshaft bearing housing and drifts).

Don't forget to fit the circlip.

High gear bearing oil seal, open side to the bearing - tap it all around (like 25-30 times) with a ball peen hammer (beat the sucker in!).

Replacing Layshaft closed-end needle roller bearing

The specially shouldered drift I had fabricated to install the layshaft needle bearing 57-1606 was supposed to ensure the bearing's correct protrusion (.073-.078") above the gearbox casing, but it turned out to have not been made correctly. Nevertheless, the correct installation was acheived by going slowly a little bit at a time.

I marked the position of the thrust washer locating peg on the casing with a permanent marker to make it easier to align the matching hole in the thrust washer while installing the mainshaft.

Insure that the bearing lip is below the face of the bronze thrust washer.

Replacing High gear and drive sprocket

  1. From the inside of the gearbox, insert high gear through the bearing and oil seal
  2. Push on sprocket with drop of oil where the flange runs in the oil seal
  3. Place the case over an open vice, sprocket down, and use a 'suitable drift' (think big) to drive the sprocket all the way onto the high gear.
  4. Fit tab washer and large sprocket nut.
  5. Tighten the nut

    Note: In Hancox's video the case is not in the frame so I'm not sure how he tightens this nut without using the chain and rear brake.

  6. Replace and tighten camplate plunger holder
  7. Replace and tighten gearbox drain bolt

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Gear Ratios & Tooth Count for 4/5-Speed Gearboxes


Icon for manual "5-speed gears - teeth" In addition to most of the info in the table below, this thread includes a gear ratio calculation spreadsheet posted by John Healey .

The following table summarizes the gear ratios and tooth count for Triumph 4/5-speed gearboxes.

Table showing gear ratios & number of teeth for Triumph 4&5-speed gearboxes

Installing Gear Cluster


Icon for manual Workshop Manual (1969 650cc Twins) Section D11: Reassembling the Gearbox

WWW icon Hughie Hancox Method: The Best! Easy Step-by-Step with Photos

WWW icon Side-by-Side Comparisons of Three Methods: WS Manual, Hughie Hancox, & Haynes

Illustration of Triumph 650 gearbox assembly with descriptions of parts

I've used several methods to assemble and install the gear cluster and in my experience Hughie Hancox's method is hands down the easiest, surest, and fastest way to do the job.

However you assemble, don't forget to seal the shifter fork shaft and the gearbox sprocket if you expect to not have oil leaks. Seal the shifter fork shaft because its drilling goes all the way through the casing. Permatex and Hylomar have both worked well for me. And keep in mind that after the gear box sprocket is installed, the shifter fork shaft drilling cannot be reached.

The layshaft thrust washers are another potential problem area. For starters, don't forget to include them in your assembly. During my first gearbox reassembly I left out the drive side thrust washer and had to take everything out and start over. I know others who have done the same.

The other important thing about the layshaft thrust washers is to be sure they are well installed over their locating pegs and that they don't fall off during assembly. A good smear of heavy grease helps.

During my first gearbox adventure I ended up reinstalling the gear cluster five times, and the transmission twice. The first time I put the cluster in it took just under two hours. The fifth time it took less than three minutes.

At that time I tried three different ways to install the gear cluster. Of the three, I found the WS Manual method (see Method 3, below) of installing the gear cluster as a unit to be the easiest. The only way I deviated from the WS Manual was to index the quadrant and camplate in 1st gear instead of using neutral between 2nd and 3rd as shown by the WS Manual (see Indexing Camplate & Quadrant below.

The next time I reassembled the gears I used the method shown by Hughie Hancox on his DVD, in which he puts the gears in place one at a time. I made several dry runs and could hardly believe how easy this method is.

The one thing I did differently from Hancox was that I did not pre-install the mainshaft and kickstarter assembly in the inner cover the way he does in his video. Instead I inserted the mainshaft by itself before putting on the inner cover and then the kickstarter parts. Next time I'll be inclined to pre-assemble the way Hancox did simply because that way the kickstarter nut can be tightened (45lbs) while the shaft is held in a vise.

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Four Variations on Gear Cluster Installation

Method 1: Juggling

  1. Install inside layshaft thrust washer using heavy grease
  2. Install camplate and orient as shown opposite
  3. Insert mainshaft
  4. Install mainshaft gears
  5. Install rollers on selector forks using heavy grease
  6. Install mainshaft selector fork (the longer of the two selector forks)
  7. Push mainshaft selector fork to rear until roller drops into camplate
  8. Possibly, use selector fork rod to manipulate/position/hold mainshaft selector fork
  9. Install layshaft
  10. Install layshaft gears
  11. Install layshaft selector fork (shorter of the two selector forks)
  12. To allow it to fit in and for its roller to enter the camplate channel, back out the mainshaft/gears/fork selector components to provide sufficient clearance

Illustration of Triumph gearbox camplate positioned in neutral between 2nd and 3rd gears

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Method 2: Juggling

  1. Hold layshaft thrust washer in place with grease
  2. Install the camplate and position as shown in Service Bulletin
  3. Install mainshaft into gearbox
  4. Slide gears onto mainshaft
  5. From the bottom, put mainshaft gear selector (inc. roller) into its position on top
  6. Temporarily hold mainshaft gear selector in place with the gear selector rod
  7. Assemble layshaft with gears and gear selector outside gearbox
  8. Place the assembly on the bottom of the gearbox
  9. Gently work the layshaft assembly forward until the gear selector rod blocks further progress
  10. Hold mainshaft gear selector in place with a finger while removing the rod and replacing it with a very long, slender screwdriver
  11. Now work the layshaft and layshaft gear selector (with roller) into place
  12. Lift the layshaft and introduce it into the Torrington bearing at the far end
  13. Holding gear selectors in place with fingers, remove the screwdriver and re-insert the rod
  14. Insure that outboard layshaft thrust washer is in place
  15. Put low gear into place
  16. Put on inner cover while positioning the quadrant as shown in Service Bulletin

Illustration of Triumph gearbox camplate positioned in neutral between 2nd and 3rd gears

Method 3: Workshop Manual Variation

When I re-assembled the gears for the fourth and final time I used the method shown in the WS Manual, i.e. introducing both mainshaft and layshaft with all their parts and the shifting arms as a unit. With enough patience it does work. While the WS Manual shows the mechanic inserting the entire assembly without the rod upon which the shifter arms travel, I achieved assembly with the rod inserted through both shifting arms.

When inserting the cluster, first tip the cluster clockwise a bit to get the roller on the mainshaft gear shifter into the camplate. Then, going in further, tip the cluster counter-clockwise to get the layshaft gear shifter's roller into the camplate. The last time I did it the whole thing took less than three minutes.

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Method 4: Hughie Hancox

I saved the best for last! Hancox assembles the layshaft, layshaft gears, and mainshaft gears in situ before inserting the mainshaft, already installed in the inner cover, through the mainshaft gears.

Nearly everyone who tries this method agrees that it is the easiest and fastest of all. For photo-illustrated step-by-step instructions, follow this link:

WWW icon Hughie Hancox Method: Step-by-Step with Photos

Thrust Washer Locating Pegs

The thrust washers at either end of the layshaft are held stationary by hardened steel locator pegs in the casing that match holes in the thrust washers. Stuff happens and the pegs get ground down. Here are some descriptions of the problem with details on replacing damaged pegs.

WWW icon "Layshaft thrust washer guide pin 76 T140"

WWW icon "57-1607 Thrust Washer Missing on 66 T100SR"

WWW icon "Gearbox problem"

WWW icon "T140-gearbox-thrust-washer-problems"

When the Bonnie's locating peg for the DS thrust washer became damaged, I took the engine to my favorite machinist and he fabricated a jig which he used to drill a new hole for a replacement peg. Photo icon "Locating peg repair"

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Indexing the Camplate & Quadrant


WWW icon "Camplate & Quadrant Indexing" Step-by-step descriptions & photo illustrations for three indexing methods

Indexing the gearbox camplate and quadrant ensures that when the gearbox inner cover is pushed on, the camplate and quadrant end up correctly positioned relative to each other as the teeth of their gears are meshed. Being one or more teeth off either way results in faulty gear shifting.

Camplate Positioning

Indexing can be accomplished with the camplate set in any one of three positions: 1st gear or 4th gear (both shown below), or in neutral between 2nd & 3rd (straight up and down, not shown below).

Photo of gearshift camplate in all 5 positions

Quadrant Positioning

For complete details and photo illustrations, follow the "Camplate & Quadrant Indexing" link just above.

Note on Replacing Gearbox Inner Cover

If an oil filter head is installed on the down tube, be sure to install the lower forward engine mounting bolt through the back of the inner cover before putting the cover in place. Once the inner cover is in place, the filter mounting bracket prevents inserting the bolt from the back. If the bolt is installed head out, it interferes with the oil lines on the inside.

Bonnie Notes

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The Fuel System

Gas tank


Icon for manual Workshop Manual (1969 650cc Twins) Section E1: Removing and Replacing the Fuel Tank

Parts iconFig.22 Gas tank

WWW icon "Bruce Hamilton: "FAQ: Automotive Gasoline" (inc. bibliography)

WWW icon "How to protect the petrol tank"

WWW icon "Best Tank Sealer"

WWW icon "Triumph paint thread" R Moulding's excellent paint thread, illustrations and discussion

WWW icon "Triumph Bonneville Paint Schemes 1959-1970" John Healy via Rask Cycle

WWW icon Tips on installing knee pads on gas tank

WWW icon "Stepless Ear Gas Line Clamps"

When securing the gas tank, always begin by tightening the rear mount first. If the front nuts are started first it makes the gas tank lift up in back. I think that's why on so many bikes the threads in the frame for the rear tank mount are stripped. That happened to my brand new 1966 Bonneville, and both of the used Bonnies I've bought came with stripped threads.

Now I use a large tie-wrap over the tank's rear mounting tab (bolt and all rubber parts in place) and through the sidecar mounting hole. Again, I begin with the tie-wrap in back and then proceed to tighten the front mounts.

The front tank mounting stud on Bonnie's timing side came loose once. The great Leon Goldick of Montreal, who painted Bonnie's gas tank, made a repair and touch-up.

The question often comes up, what to do with the gas tank over the winter season? I confess that I usually get around to draining the tank by February and then leave it empty, but this is not the greatest strategy, especially with ethanol fuel which attracts moisture - the better to rust the inside of the tank. See the link "How to protect the petrol tank" just above for a discussion of what guys do with their tanks in the winter.

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Gas Line

After reading through this WWW iconTriumphRat fuel line thread I decided, for safety reasons, to switch from classic look reinforced plastic lines to rubber hose. Not only are plastic lines more prone to leaking, in case of a fire they will melt and add gas to the flames.

Tip!When removing carburettors it is only necessary to disconnect the fuel lines from the gas taps. The carbs can then both be removed as a unit without disturbing the rest of the fuel line connections. Likewise, when tearing down the carbs, one can simply unscrew both banjo bolts and remove them and the fuel lines as a unit.

Gas Taps


The brass gas tap fuel line connectors shouldn't be so tight that they can can't be loosened by a few light raps with two or three fingers on a wrench. Avoiding over-tightening prevents the gas tap from turning and possibly breaking the seal to the tank.

Sealing Gas Taps

WWW icon BritBike Forum Discussion: "Sealing Gas Taps", Discussion of various sealing washers and methods of making leak-free connection between gas tank and gas taps. In addition to some good insights, this thread includes some funny ripost, some blowing off of steam, and, briefly, some party-line-like communication.

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Icon for manual Workshop Manual (1969 650cc Twins) Section B7: Concentric Carburettor Type 900 (Illustration)

Icon for manual Workshop Manual (1969 650cc Twins) Section B8: Removing and Replacing Carburettors

Icon for manual Workshop Manual (1969 650cc Twins) Section B9: Stripping and Reassembling the Carburettor

Icon for manual Workshop Manual (1969 650cc Twins) Section B10: Inspecting the Carburettor Components

Icon for manual Workshop Manual (1969 650cc Twins) Section B11: Carburetter Adjustments

Icon for manual Workshop Manual (1969 650cc Twins) Section B12: Twin Carburetter Arrangement

Manual icon Amal "Hints & Tips for Amal Mk1 Carburettor"

Manual icon Triumph Service Bulletin #2/73 "Checking & Adjusting the Amal Concentric Float"

Parts icon Fig.31 Concentric 930

WWW icon John Healy: "Amal Concentric Carburettors" (2017)

WWW icon John Healy: "Tuning Your Carburettor" (2013)

WWW icon Jim Bush: "Bushman's Carb Tuning Secrets"

WWW icon "Bonnie carb jetting help needed" (reading spark plugs w. illustrations)

WWW icon "Amal manuals for Monobloc & Concentric (inc. Premier) carbs"

WWW icon Jeffery Diamond: "Super-Tuning Amal Concentric" (Advertisement for booklet)

WWW icon "Notes on Rebuilding the Mark-1 Concentric Carburettor"

WWW icon Richard Whatley: "Leaking Amal Carburettors"

WWW icon "Amal Concentrics, How they Work and Tuning"

WWW icon "Motor dies just as I take up throttle cable slack" Electrical or Carb? Informative thread

WWW icon "Pin gauges for needle jets" Long, informative thread on needle jets

WWW icon "Variations within the 930 Amal Concentrics" TR7RVMan describes Amal Mk1 & Premier differences

WWW icon TR7RVMan offers some good tips on cleaning carbs

Video icon YouTube Raber's Tech Tips, Episode 6: Triumph 1971 T120 Bonneville Amal Carb O-ring Installation

Random Notes

Tip!The stiffness of these small o-rings makes getting them on difficult. Make the job a little easier by warming the o-rings in hot water and then rolling them on.

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Carburettor to Adaptor O-Rings


WWW icon YouTube Raber's Episode #6 Video

WWW icon Triumph 650 Carburettor Mounting Methods 1966-1970+

Compatiblity The Triumph parts manuals show several different o-ring set-ups for use between the Concentric carb body and the T120R carb adapters. The #6 1968 parts book lists a thick o-ring (Amal 244/1048) used in conjunction with an insulating block and joint washer. The #7 parts book for 1969 shows a skinny o-ring (622/101 99-0552). The 1970 parts book deletes the insulating block and joint washer and introduces a new thick o-ring (70-9711).

Although the 70-9711 o-ring doesn't appear in Triumph's parts books until 1970, it was actually introduced sometime in late 1968. My Bonnie, an early 1969 model, was fitted with the 70-9711 thick o-ring, and not the thin 622/101 shown in #7. The 'Mounting Methods' table (link just above) summarizes the parts book listings for Triumphs between 1954 and 1970.

While the thin Amal o-ring was used most often in conjunction with an insulating block (E2968) and a joint washer (NA43A), the thicker 70-9711l o-ring is used solo, without joint washer or insulating block. The thin o-ring relies on the insulating block to reduce heat transfer between the engine and the carburetter, while the thick ring reduces heat transfer by creating an air gap between the engine and the carb.

In addition to being a more efficient heat insulator, the thicker 70-9711 o-ring reduces the chance of warping the carburetter flanges caused by uneven or over-torquing the carburetter's mounting bolts.

A dab of grease helps keep the o-rings in place while you carefully fit the carburetter to the mounting studs. Next it's finger yoga putting on the rubber insulating rings, cupped washers, and lock nuts, all the while holding the carb ever so slightly off the adapter so the nuts will clear the casting around the ticklers as they are started. Once the self-locking nuts are started, tighten them evenly from side-to-side until there is a .040" to .060" gap between the carb flanges and the adapters.

Amal Concentric 930 Cross-Section

Cross section drawing of an Amal Concentric 930 Carburetter

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Amal Concentric Carburettor Parts


Manual icon Amal "Parts to Tune Up - Amal Mk1 Carburettor"

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Summary of Carb Specs & Settings

Main jet size220190
Needle position Up = richer22 (middle)
Needle jet size.106.106
Idle speed adjustment screw 1 1/2 out
Idle air adjustment
Screw out for leaner, in for richer
2 1/4 - 2 1/21 1/4 - 1 1/2

Choke Assembly

If your Amals are fitted with chokes and you decide to remove them, Amal makes a blanking screw: Amal part number 4/137. Otherwise the small hole can be filled with epoxy.

Float Bowl Flooding


WWW icon StuartMac's easy method to pinpoint float bowl problem

Tool icon Triumph Service Bulletin #2/73: "Checking & Adjusting the Amal Concentric Float"

If a carburetter is flooding frequently or, worst case, overflowing fuel, it is likely due to either the float not rising (float holed and filled with gas or hung up on the float bowl gasket) or the float needle not seating well (needle worn out or dirt lodged beneath it).

Another possibility is that the fuel level is simply adjusted too high. That adjustment can theoretically be made by lowering the float needle seat. Tricky, but the Triumph Service Bulletin #2/73 (link just above) is there to guide you:

Tip! An easier way to adjust the fuel level in the float bowl is to replace plastic bowls with Amal 'stay-up' floats. In addition to being impervious to the effects of ethenol, 'Stay-ups' have adjustable tangs holding the float needle.

Float Bowl Leaking

Fuel leaks from the float bowl are sometimes the result of over-tightening the float bowl screws which causes the bowl to warp. If the leak occurs after changing the gasket, or after the bike has been sitting for a period of time with no fuel in the bowl, the leak may cure itself after the gasket has soaked and swelled up sufficiently to make a good seal. I have also stemmed this kind of leak with some Hylomar smeared on both sides of the gasket.

The official remedy is supposedly to flatten the float bowl by gently rubbing it on a sheet of very fine abrasive paper over a completely flat surface. Be aware, though, that removing an excessive amount of metal will affect the height of the float and float needle.

Assembling Cable, Spring, Air Slide, & Needle Jet/Clip

When refitting cable to air slide, don't try to compress the spring against the carb cover, away from the cable end. Instead, pinch the exposed (slack) wire cable with finger and thumb and push the cable (and spring) towards the bottom of the air slide until the cable pokes through the other side. So, compress the spring against the air slide, not the cover.

When installing the needle jet and its clip - that's when to scrunch the spring up against the carb cover, gently hanging the bottom end over and outside the carb body while you drop in the needle and clip.

Cleaning the Pilot Jet

I've been using a guitar string to clear the idle jets, but some say this just pokes the dirt back upstream where gas will eventually wash it back down to the jets. John Healy says to use a#78 drill through the pilot air screw hole to pull the dirt out of the jet and downstream:

"Use a #78 (.016") drill mounted in a piece of hobby brass tubing works the best. If you twirl it between your thumb and fore finger as you offer it, it pulls the swarf downstream of the jet to be washed away by the flow of fuel."

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Tuning the Mk1 Concentric Carburettor


Icon for manual Workshop Manual (1969 650cc Twins) Section B11: Carburetter Adjustments

Manual icon Amal "Parts to Tune Up - Amal Mk1 Carburettor"

Manual icon Amal "How to Tune - Amal Mk1 Carburettor"

Manual icon Amal "Tuning Twin Carburettors - Amal Mk1 Carburettor"

WWW icon Getting a base setting for carbs Peg's excellent carb tuning method, start to finish

Adjusting Low Speed Mixture & Idle Speed & Synchronizing Carburettors

The Workshop manual explains how to sync carburettors in Section B12: Setting Twin Carbs but forgets to mention final adjustment of cable adjusters.

Here is the basic routine for adjusting low speed mixture, idle, and synchronizing. For more details be sure to read Peg's post above!

  1. Slack cable adjustors off completely
  2. With one plug off, start and adjust air and idle screws for good idle
  3. Perform same adjustment on opposite cylinder, matching idle RPM of first
  4. Start on 2 cylinders and adjust both idle screws out the same amount
  5. Open cable adjusters, one at a time, until idle just starts to rise
  6. Back off one turn
  7. Using chopsticks, check to see that both slides lift at the same time

It's a good idea to open the twist grip and then let it snap shut once or twice in between checking new synchronization settings for the cables.

Initial Synchronization of carburettors (no Low-speed adjustment)

See Amal Mk1 tuning links.

  1. Remove air cleaners
  2. Back idle adjustment screws all the way off
  3. Turn idle screws back in until they just touch throttle slides
  4. From there, screw them in 1.5 turns
  5. Adjust cables for synchronization

Mid-Range Tuning

See Amal Mk1 tuning links.

The next two sections talk about "8-stroking". If you're not familiar with the term, John Healy WWW icon describes it well on

WWW icon Gavin Eisler offers this sage tuning tip on "At half throttle, if acceleration could be better, no 8-stroking, clean running but slow to pick up maybe spits back as the throttle is opened, that's lean at the needle jet or needle position, try lifting the needle one notch..."

High Speed Tuning

See Amal Mk1 tuning links.

A plug chop is one way to determine the correct main jet size, but there is an alternative. If engine power is flat above 3/4 throttle in top gear, begin increasing the main jet by two sizes at a time until the engine '8-strokes', then go down two sizes. So, to check if installed main jet is correct size, put in a jet two sizes up. If the engine '8-strokes' above 3/4 throttle, the smaller jet is the correct size.

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Trouble-Shooting Carburation - Reading the Signs


Manual icon Amal "How to Trace Faults - Amal Mk1 Carburettor"

World Wide Web icon Follow the links below to discussions of trouble-shooting.

When diagnosing carburetter problems, it can be extremely time-saving to first fully determine whether the problem is actually carburation or actually electrical. This is not always easy as they can seemingly mimic each other.

Tip!StuartMac, on, offers us this clever method of finding out - Carburation? or Electrical?:

Then, go for a ride; if/when the misfire develops, note the rpm and twist grip position; change gear; if the misfire persists, note the new rpm and twist grip position.

Once you're sure the problem is not electrical (but always keeping an open mind!) you can move ahead to carburation. But this is a good time to note that if you haven't yet marked your throttle positions the way StuartMac described, that essential step should probably be your first move in diagnosing or tuning the carb.

Whether you're diagnosing or tuning, observations and advice from veterans like these below will help turn you into a carburetter connoisseur!

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Air Cleaners


Icon for manual Workshop Manual (1969 650cc Twins) Section B6: Removing and Replacing the Air Cleaners

Installing Air Cleaners

When using paper air filters, both air cleaners can be screwed on/off intact, but when using wire and gauze filters (thicker than the paper ones) the right-hand unit must assembled/disassembled in place due to interference from the foreword edge of the oil tank.

  1. Install the assembled air cleaner, cover, and retaining clip/screw (or assemble in place if necessary)
  2. Before threading the assembly on all the way, loosen the securing screw for the clip
  3. Now thread the filter onto the carburetter until it just stops
  4. Holding the adapter there, rotate the (loose) cover and clip until the cover is aligned properly
  5. Now back off the adaptor along with the cover and clips until you can tighten the securing screw
  6. Screw the entire assembly back on all the way and give a gentle twist to tighten it to the carburetter

Air Filters

I prefer the wire gauze units because they are reusable. At first I washed them in kerosene, but now I just wash them with hot water and dish washing detergent. A water-based degreaser would probably work well also.

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Control Cables


Parts iconFig.28, Cables

WWW icon Mike Partridge: Control Cable Tips

WWW icon Tri-Cor Cables, England Cable Chart

Lubricating Cables

Good cables last a long time if they are kept well-lubricated. Bonnie's throttle cables have been in service for seven years at the time of this writing and they are still completely serviceable.

My lubrication method is to disconnect a cable at the handlebars, tape its loose end into a funnel, fasten the funnel overhead, and pour in a couple thimbles of 10w or 20w oil to make its way down the cable overnight. Given this treatment once per riding season the cables only need an occasional few drops of oil to ferrules, nipples, and adjustors. And, of course, after exposure to rain.

Throttle Cables

Standard throttle cables for US bars are 43" - 45" depending on how they're measured.

A throttle cable routing that has worked well is for the TS cable to cross through frame beneath the gas tank to join the DS cable before they both pass between the front forks and up to the twist grip. I'm not sure what the hole in the TS headlight bracket is for, but it doesn't seem to work for the throttle cables.

When I got my Bonnie the throttle cables crossed over between the carbs and the twist grip. That is to say that the TS carb cable was connected to the inboard side of the twist grip and the DS cable went to the outboard side of the twist grip. That makes sense in terms of cable length and the routes taken, but I found balancing the carbs was more intuitive after I reversed the cables so their input and output ends were, so to speak, parallel.

Throttle Twist Grip

Use oil and not grease to lubricate the twist grip. Grease is too thick and the throttle will 'hang'.

Clutch Cable


I have successfully routed the clutch cable from the TS abutment on the outside gearbox cover through the frame beneath the gas tank to the DS and then through the front forks. However, I feel there is less friction when the cable arcs forward from the abutment and passes through the space between the gas tank and the forward gas tank bracket on the TS before passing through the front forks. A small cable-tie loosely securing the cable to the forward rocker oil feed pipe keeps everything tidy and in place.

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Speedometer and Tachometer



Icon for manual Workshop Manual (1969 650cc Twins) Section B42: Removing & Replacing the Tachometer Drive

Parts icon Fig.33 Speedometer and Tach 

WWW icon Smith's Instrument Repair Resources

Disassembly & Removal of Tachometer Drive Gearbox

Parts Reference: #7, Fig.33 Page 73 (link just above).

  1. Remove tachometer cable
  2. Remove the end cap (70-5759, Ref.#21)
  3. Remove the driving gear (70-5157, Ref.#20) by depressing the kickstarter smartly
  4. Remove securing screw (70-9332, Ref.#17) using a (7/16") (13mm) (3/16W) thin-walled socket

    Icon for left-handed threadSecuring screw 70-9332 has a Left-hand thread (Ref#17 Fig.33 P.73 #7)

  5. Tach gearbox will now separate from crankcase

After removing the gearbox from the crankcase always replace Sealing washer (70-7351, Ref.# 33 - same part used for gas taps) as well as o-rings as required.

O-rings used in the tach gearbox are as follows:

Icon for left-handed thread Note that if the tachometer drive has been replaced with a tachometer drive plug (21-1871 Ref.25 Fig.2 P.15 #7) on the DS crankcase, it has a left-hand thread also.

Lubricating Tachometer Drive Gear

Unscrew tach drive plug and add grease after cleaning out as much old grease as possible. When plug is screwed in, excess grease will be expelled at cable connection to drive unit.

Tachometer Cable Lubrication

See "Tach & Speedometer Cable Lubrication" below.

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Icon for manual Workshop Manual (1969 650cc Twins) Section A19: Speedometer Cable Lubrication

Parts icon Fig.33 Speedometer and Tach 

WWW icon Smith's Instrument Repair Resources

WWW icon - Crankbuster's "Smiths Magnetic Speedo". Crankbusters Animated assembly of Smiths Magnetic Speedo.

Speedometer Cable

The speedometer cable follows the swinging arm frame and then the main frame all the way to the speedometer head. It is held in place by three cable ties: one in front of the speedometer gearbox on the swinging arm frame, another on the main frame beneath the engine, and one on the frame near the front engine mount.

Tach & Speedometer Cable Lubrication

Tip!Because oil can "corkscrew" its way up the inner cable and into the instrument, Andy Hansen of Vintage British Cables recommends only using grease for lubrication of the tachometer and speedometer cables. And to ensure that no lubrication enters the instrument head, Andy advises us to not put lubrication on the 6 inches closest to the instrument.

After inspecting a new speedo cable I purchased from Andy I wasn't sure if it was adequately pre-lubricated as I could just barely detect a light coat of grease. I emailed Andy and he replied that his cables are indeed pre-lubricated and ready to install. That's when I realized that I'd been over-greasing the cables!

So, apply a very light coat of grease after unscrewing the collet beneath the speedo/tach head and withdrawing the inner cable. When replacing the cable, be sure to verify that the ends are properly seated in the receptors of the speedo gearbox and speedo head.

Speedo Gearbox

If you're looking for a replacement speedometer gearbox and find yourself confused as to whether you need a 1.25:1 ratio or a 15:12 ratio, chill out: do the math and you'll realize that they are the same.

Tip!Curiously, the WS Manual makes no mention of greasing the speedo gearbox, so don't overlook this crucial periodic maintenance.

Speedo gearboxes are a slip fit on the rear axle. If you have difficulty removing one, it's possible that repeated tightening of the TS axle nut has swaged the gearbox casing, causing it to bind on the axle. In such a case it may help to "unscrew" the gearbox off the axle and then file the hole to its original size. According to Don this problem is more common on OIF models.

Speedometer Problems


WWW icon - Don's informative post on trouble-shooting & fixing speedometer cable problems

A common problem with Smith's speedometers is a wavering or bouncing needle. Most frequent causes are poor cable routing, too much/too little lubrication, or use of too heavy a grease (see cable lubrication, above). An incorrect inner cable length (too short or too long) can also manifest itself this way.

If the speedo is inoperative, an electric drill (very low speed only!) to drive the cable or the speedometer head can be of help in isolating the problem.

Another common problem with Smith's speedometers is extreme stiffness in resetting the trip meter. These may help:

Some say removing the handle and spraying with lubricant or WD40 can fix this problem, but this sounds a little shakey to me As previously mentioned, oil or grease finding its way into the head is to be avoided.

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Icon for manual Workshop Manual (1969 650cc Twins) Section G1: Removing the Telescopic Fork Unit (Covers Handlebars)

Image of Triumph service bulletin #306, Triumph Service Bulletin #306: flexible handlebar mounting "Flexible Handlebar Mountings on 650s".

Parts iconFig.18 Handlebar mounting, steering damper

Parts iconFig.27 Handlebars, control levers, steering damper

WWW icon (BCS) BCS's Handlebar Chart with Dimensions

Handlebar Styles

Follow link above for the extensive British motorcycle handlebar reference, with photos and dimensions.

Late '60s Triumph handlebars are 7/8" in diameter. Handlebar styles I've tried on my Bonnie are:

The Commando bars beautifully compliment Bonnie's lines, the wider USA bars inspire confidence on the gravel, and the UK bars are at home on the concourse.

Handlebar Shock-Absorber Mounting

For the handlebar shock-absorbing mounting to work properly, the parts must be installed in the correct order and with the hemispherical washers in the correct orientation (hemispherical sides facing each other).

It is also important that the hemispherical washers have indents around their inner hole. The indents match the shoulders on the shanks of the eye bolts and if they are not present the eye bolts can be stressed to the point of breaking. (John Healy). Illustration of correct assembly of a Triumph shock-mounted handlebars

The correct order of the parts is listed below and shown in the figure to the right.

  1. Hemispherical washer (flat side up)
  2. Distance piece
  3. Steady rubber
  4. Cup
  5. Bonded bush in upper steering yoke
  6. Hemispherical washer (flat side down)
  7. Nylock nut

Traps! If an eyebolt makes contact with the head lug it can create a safety issue. For details, follow link to "Triumph Service Bulletin #306" in the Resources section just above.

Removing Handlebar Mounting Bonded Bushes from Upper Steering Yoke

  1. (Remove upper steering yoke - but not if it can be avoided)
  2. Slip 1/2BS socket over 4 1/2" x 5/16" hex head bolt with drive end of socket towards bolt head
  3. Insert the bolt through the center of the bonded bush from either top or bottom of upper steering yoke.
  4. Slip 5/16BS socket over end of bolt with drive end of socket facing away from the upper steering yoke
  5. Install a nut onto the bolt (if required, use washers as spacers)
  6. Secure the bolt's hex head in a vise
  7. Align the 5/16 BS socket with bonded bushing's outer sleeve
  8. Tighten the nut until the bushing slides out

Use similar method to install new bushings.

Handlebar Grips

Traps!It's been suggested on forums that hair spray can be used to keep handlebar grips in place. I know from experience what a dangerous idea that is. During dry weather the hair spray works fine, but even the tiniest rain shower turns it super-slippery! My grips were sliding off the bars like the proverbial greased pig - steer clear of this solution!

The old school method is friction tape - not plastic electricians' tape, but cloth friction tape. Hockey tape might work also. Wrap the tape on the bars and then give the grip a good smack to propel it over the tape.

Another solution would be Three Bond Griplock #1501C, but this is very pricey stuff!

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Rear Suspension

Shock Absorbers


Icon for manual Workshop Manual (1969 650cc Twins) Section E5: Adjusting Rear Suspension

Icon for manual Workshop Manual (1969 650cc Twins) Section E6: Removing & Refitting the Rear Suspension Units

Icon for manual Workshop Manual (1969 650cc Twins) Section E7: Stripping & Reassembling Suspension Units

Parts iconFig.13 Swing arm, rear shocks

WWW icon "Shock absorber replacements" inc. comments on Emgo, Ago, Ikon, Fournales

Disassembling Shocks

Dealing with the split ring clips at the top is much easier with two sets of hands.

Installing Shocks

When replacing the shock absorbers, don't force the mounting bushings into place from the rear of the frame bracket or from directly beneath the shock mounting holes. Instead, insert the bushings from beneath the spare hole in frame bracket and then slide them to the rear and into place. Using this technique may require a few plastic mallet taps, but it shouldn't be necessary to beat on the shocks.

At the bottom the shocks are fastened with a bolt with a plain flat washer beneath the head, and a spring lock washer and plain nut at the other end. At the top #7 shows the same bolt with no washer beneath the head and a different plain washer beneath the nut.

Top and bottom bolts are shown in #7 with the heads at the outside, but on the DS anyway the bottom bolt should be head inside or the bolt will scrape on the brake drum cover.

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Front Fork

Front Fork


Icon for manual Workshop Manual (1969 650cc Twins) Section A16: Telescopic Forks Lubrication

Icon for manual Workshop Manual (1969 650cc Twins) Section G: Front Fork Table of Contents

Icon for manual Workshop Manual (1969 650cc Twins) Section G9: Changing the Front Fork Main Springs

Parts icon Fig.17 Front Fork

Photo icon  Front Fork Components

Video icon YouTube Raber's Tech Tips, Episode #2 - Triumph 500 / 650 Front Axle Widths

Video icon YouTube Raber's Tech Tips, Episode #5 - 1967 Triumph TR6 Front Fork Disassembled

Compatiblity Mike James'  Triumph T120 Fork Changes During 1968 & 1969 Model Years (PDF)

Compatiblity Peg describes & illustrates T140 fork seals, 1973-1982. (Scroll down to 2nd post for photos).

Front Fork Gaiters

The gaiters can be removed and replaced by removing the front wheel and fender. When installing new gaiters this way the 'sticking point' can be getting the tops of the gaiters past the dust excluder sleeve nuts. A method that works well is to dig the tips of both thumbs right into the gaiter just below the "collar" at the top and push them right on.

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Removing Front Fork As a Unit


Icon for manual Workshop Manual (1969 650cc Twins) Section G1: Removing the Telescopic Fork Unit

Remove as a unit to maintain steering head bearings.

  1. Drain fork oil (see "Draining Fork Oil")
  2. Remove front brake cable
  3. Remove split clamps and front wheel
  4. Fender and fender braces can remain in place
  5. Disconnect battery
  6. Remove headlamp shell and bungee to frame
  7. Remove throttle grip and clutch cable
  8. Remove handlebars
  9. Remove steering damper
  10. Slacken seated nut on top steering yoke pinch bolt
  11. Remove fork stem sleeve nut
  12. Remove left and right stanchion tube cap nuts
  13. Support front fork... it's coming off!
  14. Use plastic mallet to tap underside of upper yoke
  15. Catch steering head ball bearings - especially the bottom ones

Removing Front Fork Legs Separately

Remove separately to maintain fork - oil seals, etc.

  1. Disconnect battery
  2. Drain fork oil (see "Draining Fork Oil")
  3. Remove steering damper
  4. Remove front brake cable
  5. Remove split clamps and front wheel
  6. Remove front fender and braces
  7. Remove headlamp shell (bungee to frame)
  8. Remove throttle grip and clutch cable
  9. Remove handlebars
  10. Remove left and right stanchion tube cap nuts (Tool icon Stanchion cap nuts wrench))
  11. Slacken lower yoke pinch bolts
  12. Spread lower yoke slots with chisel or screwdriver
  13. Thread service tool Z161 stanchion tube puller into stanchions and drive them free
  14. Remove left and right top fork covers

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Dismantling Front Fork


Icon for manual Workshop Manual (1969 650cc Twins) Section G2: Dismantling the Telescopic Fork

Icon for manual Workshop Manual (1969 650cc Twins) Section G3: Inspection & Repair of Fork Components

  1. Remove cork washer and gaiter
  2. Remove spring abutment and spring
  3. Remove dust excluder sleeve with Tool icon Dust excluder sleeve nut wrench
  4. With lower leg in vise use a sharp pull to withdraw stanchion
  5. Remove bearing nut and withdraw shuttle valve
  6. Remove lower bearing
  7. Remove pvc damping sleeve (note built-up end is down)
  8. Remove circlip to separate shuttle valve from bearing nut

  9. Remove plain washer from top of dust excluder sleeve
  10. Turn sleeve upside down and drive oil seal out with drift
    (have replacements on hand, seals are ruined)
  11. Place sleeve in (wood-faced) vice upside up and clamp loosely
  12. Use drift to drive out upper bearing and plain washer
  13. Remove "o-ring" from groove inside sleeve (renew)

  14. Manuals say the hex-base of restrictors are recessed into bottom of lower fork legs - not on Bonnie
  15. Use speed wrench and extension with 5/8" socket to hold restrictor while using 1/4"drive 5/16" socket to remove flanged screw and aluminum (copper) washer

Replacing Front Fork Seals


Icon for manual Workshop Manual (1969 650cc Twins) Section G3: Renewing the Front Fork Seals

Notes on front fork oil seal replacement:

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Stanchion Tubes


Icon for manual Workshop Manual (1969 650cc Twins) Section G6: Reassembling and Refitting the Telescopic Fork Unit

Compatiblity Triumph made several modifications to the stanchion tubes and none of them are compatible with each other. For more details, follow link above to Mike James' illustrated guide above.

Refitting Stanchion Tubes

Tool icon Use service tool Z161, stanchion tube puller to draw stanchion tubes into top lug.

Refitting Fork Assembly to Frame

To refit the complete front fork assembly (including the upper and lower yokes).

  1. Hold ball bearings in place with grease
  2. Fit lower yoke and stem through frame and top yoke
  3. Use a short bungee cord over the frame and through the stanchion tube holes in lower yoke to keep the stem from dropping
  4. Place cupped dust cover over ball bearings on top
  5. Use stiff wire to hold down the cupped dust cover and prevent top ball bearings from escaping - over the cover and around the frame
  6. Fit top yoke over the stem, screw on fork stem sleeve nut (The new fork stem sleeve nut used with the steering damper was difficult to rotate inside the upper yoke so I tapped it into the yoke and then rotated the yoke to get the sleeve nut started threading on the stem and then used the 1/2" drive ratchet drive with a socket to tighten it down)
  7. When stem nut contacts the wire, back-off, remove wire, and then continue to adjust the sleeve nut
  8. Tighten sleeve nut ONLY enough to remove fork play
    (Check by pulling and pushing on ends of lower legs)

Aligning Front Fork


Icon for manual Workshop Manual (1969 650cc Twins) Section G7: Telescopic Fork Alignment

When replacing front wheel and axle, the front fork should be aligned as follows.

  1. With wheel and axle and axle caps in place, finger tighten the axle cap bolts on both sides
  2. Using 1/2" wrench or socket, tighten the axle cap bolts on one of the axles
  3. Compress the front fork as much as possible (tie-downs work well)
  4. Tighten the axle cap bolts on the side where they are finger tight

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Steering Head


Icon for manual Workshop Manual (1969 650cc Twins) Section A14: Greasing the Steering Head Ball Races

Icon for manual Workshop Manual (1969 650cc Twins) Section G4: Renewing the Steering Head Races

Icon for manual Workshop Manual (1969 650cc Twins) Section G8: Adjusting the Steering Head Races

WWW icon Part numbers for cones & cups to replace loose bearings

WWW icon Lowbrow Customs Tapered roller bearing conversion kit

WWW icon CBS description of 2-piece drift for installing steering head bearings

Refitting Upper & Lower Yokes

These steps are for installing the upper and lower yokes separately from the fork assembly - for refitting as part of fork assembly, see Refitting Fork Assembly to Frame just above)

  1. Hold ball bearings (20 top and 20 bottom) in place with grease
  2. Fit lower yoke and stem through frame and top yoke
  3. Use a short bungee cord over the frame and through the stanchion tube holes in lower yoke to keep the stem from dropping
  4. Place cupped dust cover over top ball bearings
  5. Use stiff wire to hold down the cupped dust cover and prevent top ball bearings from escaping - over the cover and around the frame
  6. Fit top yoke over the stem, screw on fork stem sleeve nut

    (The new fork stem sleeve nut used with the steering damper was difficult to rotate inside the upper yoke so I tapped it into the yoke and then rotated the yoke to get the sleeve nut started threading on the stem before using 1/2" drive and socket to tighten the nut)
  7. When upper yoke contacts the wire, back-off, remove wire, and then continue adjusting the sleeve nut
  8. Tighten sleeve nut ONLY enough to remove fork play
    (Check by pulling and pushing on ends of lower legs)

Steering Damper


Parts icon Fig.18 Steering Damper

Parts icon Steering Damper Fitment by Years

WWW icon Steering damper

In 1969, only the TR6C came equipped with a steering damper. I found the dampers on my '66 Bonnevilles so useful that I retro-fitted one on Bonnie. Very good on bad roads and windy days, just be sure to loosen it when you get into town!

My theory is that wind affects down-road trajectory not so much by its action on the bike, but on the upper body of the rider. The wind pushes the rider, whose shoulders move, and the motion is transmitted to the handlebars. The steering damper virtually eliminates the effect.

When I retro-fitted a damper to Bonnie I neglected to fit 'locating pin' 97-2107, which, I learned recently from TriumphDave's post, prevents the sleeve nut from falling off.

Steering lock

The steering lock cylinder is held in place by a counter-sunk set-screw. The set-screw hole is covered over by a plug which must be dug out before removing the set-screw and lock cylinder.

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Axles, Wheels & Brakes



Parts icon All Front & Rear Axle Retainers, Support Rings, and Dust Covers Illustrated
This photo shows the top and bottom sides of all grease retainers, dust covers, support rings, backing rings, and retaining rings on the front and rear wheel axles. It also includes dimensions, part numbers, and reference numbers.

Parts icon Front Axle bearings, covers, rings, and retainers
This photo shows the orientation of all parts on the front axle, including the dust cover, retaining ring, support ring, grease retainer, bearings, and circlip.

Parts icon Rear Axle bearings, grease retainers, and retaining and backing rings illustrated
This photo shows the assembly order of the rear axle bearings, grease retainers, retaining ring, backing ring, and speedometer gearbox.

Parts icon Rear Axle nuts and distance pieces
A photo showing the assembly order of the rear axle inner and outer nuts and distance pieces.

Compatiblity Mike James'  Triumph T120 Fork Changes During 1968 & 1969 Model Years (PDF)

Front Axles

CompatiblityTriumph 650s used three different width axles: pre-unit, unit through 1968, and 1969 and on.

Don't miss Mike James' detailed reference to fork and axle changes during 1968-1969-1970. Link just above.

Front Wheel


Icon for manual Workshop Manual (1969 650cc Twins) Section F1: Removing & Refitting Front Wheel

Parts icon Fig.19 Front Wheel

Icon for manual Workshop Manual (1969 650cc Twins) Section F: Wheels, Brakes, and Tires Table of Contents

Icon for manual Workshop Manual (1969 650cc Twins) Section F9: Wheel Building

Icon for manual Workshop Manual (1969 650cc Twins) Section F10: Wheel Balancing

Icon for manual Workshop Manual (1969 650cc Twins) Section F14: Sidecar Alignment

WWW icon Replacing Rims - Devon vs Central

Tool icon Wheel Bearing Locking Ring Wrench

The Nave Plate

Nave (knot knave) is a British term for a metal cover of a wheel hub, especially one which is chrome, stainless steel, or otherwise decorative. So, a hubcap.

To remove it, some say have at it with a couple of screwdrivers on the three tabbed spots. But removing the Triumph nave without permanant disfiguration may require at least a bit more finesse than that.

One proposed technique, that I've not tried, but sounds good, is to pry all three tabs simultaneously using hardwood sticks. The tips of the sticks must be whittled down a bit so they engage the tabs positively and either an assistent is required or elbows and knees must be pressed into service.

Front Wheel Bearings


Icon for manual Workshop Manual (1969 650cc Twins) Section F8: Removing & Refitting Wheel Bearings

Photo icon Photo & Drawing: Front Wheel Axle Parts

Icon for left-handed thread Front wheel bearing TS retaining ring 37-0582 has a left-handed thread. (Ref.15 Fig.19 P.49 #7)

Tip! Special tool Z76 (61-3694) can be used to remove the retaining ring.

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Front Wheel Brakes


Icon for manual Workshop Manual (1969 650cc Twins) Section F5: Brake Adjustments

Icon for manual Workshop Manual (1969 650cc Twins) Section F6: Stripping & Reassembling Brakes

Icon for manual Workshop Manual (1969 650cc Twins) Section F7: Renewing Brake Linings

Parts icon Front Brake Shoe Illustrated

WWW icon Tips on renewing and tuning vintage motorcycle brakes

WWW icon Stuart provides many details on various Triumph hub, anchor plate, & axle setups

WWW icon The Village Idiot, RPW, and others divulge their best brake tuning secrets!

Removing Front Brake

  1. Apply front brake using a tie wrap
  2. Use a 1 1/8 deep socket to unscrew the backing plate nut (RH)
  3. Pull out the backing plate assembly and note the position of the twin leading shoes (TLS)


When reassembling the brake, note that:

Replacing Front Brake

  1. When replacing the backing plate assembly, don't tighten the nut fully
  2. Center the shoes by lightly tapping the backing plate with a plastic mallet with the brakes slightly on
  3. If necessary, adjust the brake lever as the shoes become centered
  4. Undo the pin on the brake arm and pull the front shoe's lever until both shoes are snug
  5. If adjustment is required, loosen the locknut on the clevis joint and turn the clevis until both shoes are contact the drum equally
  6. Keep the shoes centered as you tighten the backing plate nut by applying the brake firmly

Adjusting Front Brake

From the WS Manual evidently:

  1. Slack off the brake cable at the handlebars to remove all tension on the linkage
  2. Remove the locking pin connecting the two cam levers together
  3. Apply both cam levers stiffly
  4. Adjust the link rod length until the loose end just fits into the other cam lever
  5. Re-insert the locking pin and tighten the locking nuts on the lever
  6. Make an adjustment at the hand lever for a slight slack in the cable
  7. When adjustment is complete, rotate the wheel rapidly in its normal direction
  8. With the wheel spinning rapidly, apply the brake hard to stop the wheel abruptly

But as always, there's more to it than that. Be sure to see "brake tuning secrets" link above under Resources.

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Front Wheel Fender Brackets/Stays


WWW icon StuartMac's tips on fitting the front fender stays to fork

Tip! To remove the front wheel without disturbing the fender and fender braces, deflate the tire.

The front fender brackets (Ref.5 in Fig.26 Fenders ) fit on the lower fork legs pointing forward with the bottom angle projecting upwards.

The bolts (Ref.23) which fix the stays to the brackets face nuts out (Ref.24).

Figure 26 (#7) doesn't show how the forward and center stays (Ref.2 and Ref.3) fit onto the fender brackets (Ref.5). They should both be fixed to the outside of the fender brackets Photo icon as shown here.

If the fixing bolts are hard to get through the stays and bracket, slacken the bolts holding the stays to the fender and then give the bolts a rap with the plastic mallet.

[The mounting hole for the bottom stay (Ref.4) in Bonnie's used replacement lower fork leg is threaded, so the bolt must be threaded in and out.]

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Rear Wheel


Icon for manual Workshop Manual (1969 650cc Twins) Section F: Wheels, Brakes, and Tires Table of Contents

Icon for manual Workshop Manual (1969 650cc Twins) Section F4: Front & Rear Wheel Alignment

Parts iconFig.20 Rear Wheel

WWW icon Replacing Rims - Devon vs Central

Rear Wheel and Chain Guard

Removing Rear Wheel (& Chain guard)


Icon for manual Workshop Manual (1969 650cc Twins) Section F2: Removing & Refitting Rear Wheel

Icon for manual Workshop Manual (1969 650cc Twins) Section F3: Removing & Refitting Quickly Detachable Wheel

Either the wheel can be removed by lowering it through a specially-designed service table, or the back of the bike can be hoisted up to provide the required clearance between wheel and fender.

Procedure to remove rear wheel:

  1. Remove rear brake adjuster and disconnect brake rod
  2. Disconnect wires to stoplight switch
  3. Remove spring between brake rod and stoplight switch
  4. Remove master link and disconnect chain
  5. Remove speedometer cable
  6. Remove nut holding rear brake torque stay to anchor plate
  7. Slacken bolt holding rear brake torque stay to swing arm
  8. Disengage rear brake torque stay from rear wheel
  9. Loosen rear chain guard bolt
  10. Slacken wheel axle nuts
  11. Raise rear of chain guard
  12. Remove the rear wheel
  13. Remove bolt holding front of chain guard
  14. Withdraw the chain guard

Replacing Chainguard


Parts iconFig.13 Chain guard

A nut and bolt fasten the front of the chainguard to a tab on the swinging arm frame. Replacement Parts Catalogue (RPC) #7 show the bolt inserted from inside the tab and outwards through the chaingaurd ((Ref.28,Fig.13,P.37 #7)). Some think this is an error.

For starters, oriented that way, the bolt can't be installed or removed while the fender is in place. Even more importantly, the bolt's head should be installed inside the chainguard, where otherwise any protrusion beyond the nut will snag the chain.

If you choose to install the bolt through the chainguard, though, you'll have to deal with the hastle of holding the thin Philidas self-locking nut in place while you start the bolt. Peter has a solution for us:

Tip!Peter's Trick #15: "The swing arm has a welded tab to affix the chain guard. I placed a nut at the back permanently, so as not to have to use a wrench to hold it while removing the bolt that holds the guard at that point. Press fit with Loctite."

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Replacing Rear Wheel

When re-installing the rear wheel, one must properly align the speedometer gearbox and then activate the rear brake somewhat forcefully (see "centering brakes below") while tightening the inner axle nuts. To do this the easy way, with the wheel mounted on the bike, you need a very thin 1-5/16" wrench for the TS inner nut. If you don't have a suitable wrench, save lots of trouble and get one.

Before I had the right wrench, I did all the above with the tire in a bench vise. But the problem was to get the speedo gearbox correctly aligned - a very trial-and-error affair. It's so easy on the bike - get the wrench!

Off the bike:

  1. Place the wheel in position on the bike
  2. With the torque stay in place, position the speedo gearbox by eye and then take note of its position relative to the torque stay stud on the brake anchor plate opposite
  3. Remove the wheel from the bike and hold the tire upright with a bench vise
  4. Position the speedo gearbox as previously noted
  5. Tighten the inner nuts while holding the brake on
  6. Reinstall the rear wheel and torque stay and check position of speedo gearbox and cable
  7. Repeat until the proper orientation is achieved

Centering Rear Wheel Brake Shoes

The rear wheel brake shoes should be centered to the axle to prevent the brakes from 'pulsing'. To center the brake shoes, apply the brakes while tightening the inner axle nuts.

This is most easily done with the wheel on the bike because that facilitates aligning the speedo gearbox perfectly, and provides the use of the brake pedal for applying the brakes. But key to performing the work this way is the thin 1-5/16" wrench to tighten that TS inner axle nut.

Brake Torque Stay

Brake torque stay (ref 11 page 37) should go on before the plate for passenger foot peg and muffler bracket.

Both ends of torque stay are supposed to use the same nuts (14-0304)(3/8W) and spring washers (PCW73A), but on Bonnie one is thicker front) and one is thinner (rear).

The "C"-clamp on the torque stay adjusts the bottom of the chainguard with respect to the tire and the chain. It must be fit so that it rests ON TOP of the chainguard bracket to allow for adjustment. Bit of a PITA, but fitting the nut and bolt with the passenger peg and mounting plate removed is much easier.

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Rear Wheel Bearings


Icon for manual Workshop Manual (1969 650cc Twins) Section F8: Removing & Refitting Wheel Bearings

Photo icon Photo & Drawing of Rear Wheel Axle Parts

Tools icon Wheel Bearing Locking Ring Wrench

Sealed bearings are the way to go.

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Rear Wheel Brakes


Icon for manual Workshop Manual (1969 650cc Twins) Section F5: Brake Adjustments

Icon for manual Workshop Manual (1969 650cc Twins) Section F6: Stripping & Reassembling Brakes

Icon for manual Workshop Manual (1969 650cc Twins) Section F7: Renewing Brake Linings

Parts iconRear Brake Shoes Illustrated


Shouldered end of the rear wheel spindle goes to T.S. Seerear axle photo and illustration. Photo icon

Tip!If removing the brake cam lever (Ref 32 Figure 20) from the brake cam post is difficult, try this:

  1. Remove S1-52 nut and S25-6 plain washer
  2. Replace the nut, leaving it somewhat loose
  3. Apply a bit of heat to the actuation arm
  4. Place a socket over the end of the grease nipple so that it rests on the nut
  5. Gently bash on socket


Traps!When reassembling the brake, note that:

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Rear Wheel Brake Pedal, Brake Rod

Brake Pedal Wear

Over time, a Triumph rear brake pedal pivot becomes a loose fit. This would be an easy fix if Triumph had used a bushing there, but they didn't. Here's how one listee fixed the problem:

WWW icon WOL: Sloppy Brake Pedal


Brake rod cotter pin

With everything assembled, it's nearly impossible to splay the cotter pin that fastens the rear brake rod to the brake pedal lever: therefore, do it at one of these stages of disassembly:

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Rear Wheel Fender Bracket


Icon for manual Workshop Manual (1969 650cc Twins) Section E4: Removing & Replacing Rear Mudguard

Parts icon Fig.26 Fenders


Bracket fits inside the rear frame loop. See TBA photo.

Rear fender bracket on frame 1/2" bolts (same bolt used for oil bottle bracket).

Rear Wheel Fender


Parts icon Fig.26 Fenders

WWW icon ""Fender Drill Pattern Templates", Good tips on fitting a new rear fender


  1. Nut from bolt that fixes front of fender
  2. Nuts from bolts through fender bracket at shocks
  3. Nuts that clamp fender to frame loop
  4. Tail light


Note that the two rear fender bracket mounting bolts (14-0113) Parts icon(Ref 32 Figure 26) must be installed before putting on the fender.

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Rear Chain


Icon for manual Workshop Manual (1969 650cc Twins) Section C11: Rear Chain Alterations & Repairs

Icon for manual Workshop Manual (1969 650cc Twins) Section A13: Rear Chain Lubrication & Maintenance

WWW icon  Drive chain lubrication Opinions on chain lubrication - take your pick

WWW icon  New rear chain Long thread on chain specs/brands with an emphasis on Renold chains

WWW icon Final drive chain Regular vs sealed (o-ring) chain and more Renold comments

Removing Rear Chain

Tip!When lubricating or working on the chain, use a short piece of rain gutter to contain the mess.

Tip!If the chain happens to fall off the rear sprocket, it can be replaced by inserting the tapered end of a chopstick through the spokes and into the hole at the end of the chain and using it to drag the chain far enough back to engage the sprocket and be pulled around using the wheel.

Replacing Rear Chain

Traps!The orientation of the master link clip is critical - the closed end of the clip must always be at the front as it travels around in the direction the chain is moving. You can think of the clip as a spawning fish that's swimming up the back of the rear sprocket - but with the flow, not against it.

Tip!Replacing a master link on the side away from you is awkward. Instead, insert a spare master link from your side of the wheel - it keeps the ends aligned perfectly and gives tactile reference for installing the actual master link from the opposite side.

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Checking Rear Chain for Wear


WWW icon ""Measuring Chain Wear", Greg Burns

As Burns points out in his article "Measuring Chain Wear", chains do not stretch, they become longer due to the pins wearing an oblong pattern in the bushes.

When wear progresses to the point the chain is no longer a perfect match with sprocket teeth, wear to both sprockets quickly accelerates.

The workshop manual describes a standard method for checking wear:

How much wear is acceptable? Opinions differ. Extrapolating from 20 links to 100, the manual sets out 1.25" (1-1/4) as the maximum acceptable increase in length over 100 links.

However, Burns claims that "Most chain manufacturers limit chain wear to approximately .006" per link". That works out to .6" max wear per 100 links, or just under half what the manual considers maximum acceptable wear.

Which is right? I incline toward the figure suggested by Burns for the simple reason that a new chain costs less than a new chain and two new sprockets. And a lot less trouble to change!

Cleaning the Rear Chain

For asphalt riding I clean and lubricate the chain at each oil change, or every 1,000 miles for Bonnie. When I'm mostly riding the gravel I clean the chain every 500 miles.

Tip!Kerosene used in chain cleaning can be reused many times. Simply allow the suspended particles to settle and then gently pour off the clear kerosene into a clean container, ready for the next cleaning.

Lubricating the Rear Chain

Off the bike, after a cleaning

In an old pan, immerse the clean chain in heavy (summer) chain saw bar oil for 20 minutes or more. Next, hang the chain overnight to drain excess oil. Next day, wipe the chain lightly with a clean rag before reinstalling.

Pull the clean, lubricated chain back on with the old chain.

On the bike, after a ride

Always lube a mounted chain when it's warm after a ride! Oiling a cold chain just makes a mess on the floor. Applied to a warm chain, oil will penetrate inside the rollers where it's needed instead of dripping off.

Using the tapered tip of a gear oil container, I apply heavy chain saw bar oil to the chain while I spin the rear wheel. It's surprising how much oil a warm chain will "absorb", but don't carried away! If oil drips off a warm chain the application was excessive and the excess will be flung off directly during the next ride. Performed regularly after every ride, very little oil is needed with each application.

Traps!Do not over-lube! An excess of oil can seep into the rear wheel brake drum and spoil the brake shoes.

Checking & Adjusting Rear Chain Slack

With the bike on the center stand, check rear chain slack half-way between front and rear sprockets on the lower run. With the chain in its slackest position, use a finger to push it up and then down. The distance between those two points is the chain slack and should normally be 1-3/4".

When properly adjusted (1-3/4" slack on center stand), the chain will look to be too slack, but when a rider compresses the rear springs the swing arm raises, tightening the chain.

Tip!To learn a cool way to find the slackest place in the chain (hint: a little dab'll do ya!), and a way to get an accurate measurement of the slack, click this link (eye-roll) to TR7RVMan's complete description of rear chain adjustment on As always, Don has the good stuff!

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Icon for manual Workshop Manual (1969 650cc Twins) Section F11: Removing & Repairing Tires

Icon for manual Workshop Manual (1969 650cc Twins) Section F12: Security Bolts

Icon for manual Workshop Manual (1969 650cc Twins) Section F13: Tire Maintenance

Manual icon Dunlop Tire Tips and Technical Specifications (PDF).

WWW icon "Best tyres for nervous handling 1969 TR6C...." (tires & tire pressure)

WWW icon "Tyres!!" (tire preference thread)

Tire Pressure

Traps!The 1969 Triumph Workshop Manual gives an incorrect tire pressure for today's tires.

Although the General Data section of the Triumph Workshop Manual for 1969 Unit Construction 650 Twins states a tire pressure of 24 lbs for front and rear, it must be understood that the modern versions of even vintage tires are made with far superior materials and technology than the originals, and they are not only capable of higher inflation pressures, they require them.

The first few years I had Bonnie I used the WS manual's recommendation of 24/24. Eventually I took notice of the weird wear pattern on my front tires: they were cupping badly. The tire guy said raise the air pressure so I did, to 30/30. End of cupping problem.

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Front Tire and Tube

Dunlop K-70, 3.25 x 19

Rear Tire

Dunlop K-70, 4.00 x 18

Tubes for Dunlops

Put valve stem to yellow dot.

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Frame - Stands - Tin - Pegs


Icon for manual Workshop Manual (1969 650cc Twins) Section E: Frame and Attachments Table of Contents

Icon for manual Workshop Manual (1969 650cc Twins) Section E11: Frame Alignment

Icon for manual Workshop Manual (1969 650cc Twins) Section E12: Repairs (Frame)

Icon for manual Workshop Manual (1969 650cc Twins) Section E13: Paintwork Refinishing

Swinging Arm


Icon for manual Workshop Manual (1969 650cc Twins) Section E8: Removing and Replacing the Swinging Fork

Icon for manual Workshop Manual (1969 650cc Twins) Section E9: Renewing the Swinging Fork Bushes

Parts iconFig.13 Swinging Arm, Rear Shocks

WWW icon John Healey gives some sage advice on removing & replacing swinging arm bushing.

WWW icon And here are a few more tidbits on swinging arm frame bushes, bobbins, and bolts..

Swinging Arm Incompatibility

Compatibility icon In 1966, Triumph moved the speedometer drive from the gearbox to the rear wheel axle. To accomplish this the axle end of the swinging arm frame was widened by 1/4". This means the 1966-1970 unit 650 swinging arms are incompatible with the earlier ones.

Removing Bushes

Removing the bushes involves use of a substantial blunt force object and the proverbial "suitable drift" placed against the protruding edges of the inner ends of the bushes. A 2-lb sledge, a 1/2-inch drive extension, and a 13/16" deep socket whose end was ground to make a square edge worked admirably for me. Two or three solid blows got them moving and five or six more drove them all the way out.

Replacing Bushes

Before installing the new bushes, polish the bore of the swinging arm frame where the bushes go. I used 600 wet/dry followed by 1500. After the bores are good and smooth, give them a generous smear of grease before introducing the new bushes.

For an amateur like myself, the tricky part to putting in the new bushes is to get them to go in perfectly straight. The good news is, it's easy if you know a very simple trick. Peter knows how to home them right in with confidence:

Tip!Peter's Trick #17: "To ensure that bush goes in straight , chuck it in lathe , and turn by hand all the while placing a pencil on the tool post and up against bush. After making the first concentric pencil mark, make 4 or 5 more, each about 1/16" apart. You can do the same thing by placing a bush on edge and a pencil point against it. Turn the bush by hand to make the first mark, then add spacers under either the bush or the pencil to make the remaining marks."

Installing swinging arm bushes using all-thread and nuts and bolts

There you have it. I couldn't believe how easy it was to keep the bushes "on-course". The concentric lines took all the guess-work out of starting the bushes on their way perfectly straight and keeping them straight all the way in. Don't be tempted to skimp on penciled circles - I made just three, but another time I would make quite a few more than that just for the peace of mind they bring.

So using the first line as a guide, tap the bush in using a plastic mallet. Once the bushes are off to a good start there are several choices: continue tapping them in with the mallet, or (better) draw them in using a piece of all-thread with a nut and washer at each end; or alternatively, press them in using a twin-screw woodworking bench vise.

Once both bushes are flush with the ends of the swinging arm frame they can be driven in the final 1/8" or so using a drift or a deep socket - a 1-1/8" Harbor Freight deep socket did the trick for me.

Reassembling & Replacing Swinging Arm Frame

(Note: Don't be tempted to put the shocks on before the swinging arm because they'll just be in the way).

In the swinging arm frame, assemble the two "sleeves" (Ref.5, Fig.13), spacer (Ref.6), flanged washers (Ref.7), and new o-rings (Ref.15), packing with grease as you go.

Next, using a wooden dowel to help line things up, insert the long S620 bolt (Ref.8). Loosely thread the nut on and use a grease gun to fill the cavity with grease. This will help keep everything in place while you install the swinging arm frame to the main frame.

Now remove the long bolt and offer the swinging arm frame to the brackets on the main frame. Use a plastic mallet to insert and position the swinging arm frame in the brackets until you can insert the bolt.

Remember that the DS main frame bracket is threaded for the S620 bolt, so insert the bolt from the TS.

Getting the long bolt inserted and lined up to thread into the DS of the main frame can be a fussy job. If fidgeting around and using a plastic mallet to align the swinging arm frame doesn't work, try using an impact screwdriver with a 9/16 BS or 7/8" socket. With a plastic mallet, tap the driver while slowly turning the bolt and it should start threading on.

Peter recommends at this point raising and lowering the swinging arm frame to be sure the shock mounts line up.

Torque the long bolt's nut to 50 pounds. If the swinging arm frame binds too much, back it off very slightly until it's free.

After tightening the bolt in the frame, install the tab washer (F5944, Ref.9) and S545 nut (Ref.10, Fig.13).

Now nip down the nut and fold the tabbed washer and you're done, right? Whoa, not so fast!

Tip!Peter's Trick #23: "No torque spec is given for the S545 nut at end of the long bolt (S620). What I do is place a pinch of blue Loctite and tighten. Before bending the tab washer, I put a few miles on the bike, then I re-tighten S545 for the last time before bending the tabs to suit."

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Parts iconFig.12 Side stand


Easier to remove with stand folded against frame. Use 3/4" wrench to remove nut (faces out) and then give the bolt a rap to loosen up and start on its way out. Then open the stand and wiggle while pulling on the bolt. Slip the spring off after the bolt is removed.


Nut is up and out or it will be in the way of the spring.

Easiest way to get it on is to put the spring in place on the frame and the sidestand and then pull the sidestand into place.

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Center Stand


Parts iconFig.12 Center stand

WWW icon "Centerstand spring"

WWW icon "Centre stand spring fitting"

WWW icon "Bonneville center stand (twisting)"

WWW icon "Two Easier Ways to Install a Centerstand Spring"

Center Stand Compatibility

Compatibility issue iconOver the years Triumph made many changes to the 650 center stands and mounting hardware. Here's a chart that gives the correct part numbers for stands and hardware year-by-year from 1964 to 1985.

Replacing Center Stand Spring

Ever arm-wrestle a center stand spring? They're small but mighty! Many swear words have been uttered during center stand spring installations, but happily, there are techniques which can reduce, and possibly even eliminate the amount of brute strength required.

The easiest moment to install a center spring is before putting the stand on the frame and before putting the engine in the frame. Simply flip the frame upside-down and hold it down with your feet, using a towel to protect that new powdercoat of course. Then, hold the loose stand close enough to the frame to slip both ends of the spring into place, and then holding the stand by the legs, pull it into position and slip the bolts in. Easy-peasy! Note this technique relies on pulling instead of pushing.

The job becomes more difficult when the engine and center stand are installed in the frame, but see "Install Center Stand Spring Using String"

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Left/Right passenger footrest brackets


Parts icon Fig.29 Passenger Footrest


Remove left-hand bracket to make it easier to access the bolt holding the chainguard "C" clamp to the torque stay.

Brackets need to be slack to insert bolt for rear footpegs from behind - best to pre-assemble.

Rear Frame


Icon for manual Workshop Manual (1969 650cc Twins) Section E10: Removing & Replacing the Rear Frame

The 23/34 bolt on the bottom is 5/8" used 1/2" socket.

The 21/34 bolt head is also 5/8", but its 21/34 nut is 11/16", spanner for the former and 1/2"socket for the latter.

Powder Coating

Bonnie's frame and tinware Photo icon have been powder coated, as well as the following parts:

Not powder coated:

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Battery Carrier


Parts iconFig.24 Battery Carrier

Parts iconFig.23 Oil tank

Photo icon Battery Carrier/Oil Tank Mounting (2 photos)

Photo icon Battery Carrier (8 photos)

Reinstalling Battery Carrier and Oil Tank


Icon for manual Workshop Manual (1969 650cc Twins) Section E3: Removing & Replacing the Battery Carrier

There may be better ones, but this order of assembly works ok

  1. Insert rubber spigots (82-6673) into oil tank
  2. Place rubber grommet (82-6039) and lower oil tank mount bracket (82-6147) into the loop for the bottom oil tank mount
  3. With bottom of oil tank raised towards you, offer it to the frame, rotating it down into place with a sideways wiggle to make the froth tower clear the mounting bracket on the frame.
  4. Insert screwed peg 82-7510 from left to right for left hand tank mount
    Lubricate with Murphys soap or WD-40 and tap it in with a plastic-faced mallet or squeeze it in with water pump pliers (protecting finished surfaces with a few layers of rag)
  5. Insert screwed peg 82-7510 from right to left for right hand tank mount
    Lubricate with Murphys soap or WD-40 and tap or squeeze it in To get enough of a swing, the strap can be pulled up
  6. Put on plain washers (60-4248) and nuts (82-0879)

    Regarding the next 4 steps: it's much easier to put the rubber spigots (82-6673) inside the battery holder straps and then push them onto the frame lugs then it is to put the spigots on the lugs and push the carrier straps over them.

  7. Insert rubber spigot (82-6673) into the long (rear) battery holder strap (82-8028)
  8. Lubricate the spigot and push it and the rear battery holder strap onto the rear frame lug
  9. Insert rubber spigot (82-6673) into the short (front) battery holder strap (82-9255)
  10. Lubricate and push onto the front frame lug
  11. Connect the oil tank to the batter holder straps with bolt (14-0103), rubber washer (82-6968), plain washer (60-4248), and locking nut (14-0701).
  12. Adjust oil tank for clearances and low stress and tighten fasteners

See also: Oil Tank



Icon for manual Workshop Manual (1969 650cc Twins) Section E14: Fitting Replacement Seat Covers

Parts iconFig.25 Seat, side panel

To remove seat, first remove left side panel, then remove bolts for just one seat hinge and slip the other one off.

Installing seat latch: push latch part way through its frame, insert spring and washer, then the rest of the way through. Keep spring and washer in place with right-angle pick while inserting cotter pin.

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The Electrical System


Icon for manual Workshop Manual (1969 650cc Twins) Section H: Electrical System Table of Contents

Icon for manual Workshop Manual (1969 650cc Twins) Section H-Intro: Electrical System Introduction

WWW icon MagnetoMan: "Rewiring a Motorcycle"

WWW icon RF Whatley: "Electrical System Grounding"

Trouble-Shooting Electrical Problems


Icon for manual Workshop Manual (1969 650cc Twins) Section H2: Trouble-Shooting the Ignition System

WWW icon ""Fault-Finding Flow-Chart for Motorcycle Charging Systems"

Short Circuit

If your bike is blowing fuses, this trouble-shooting tip from John Healy will be a great help in tracking down the short: replace the fuse with a 12v light bulb and then begin disconnecting circuits one at a time. When the light goes out you're found the circuit which is shorted. Start looking for faults such as worn insulation or loose bare wires.

Lucas Wiring Color Codes

Lucas electrical wiring color code chart

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Wiring Diagrams


Icon for manual Workshop Manual (1969 650cc Twins) Section H20: Wiring Diagrams

Icon for manual Workshop Manual (1969 650cc Twins) Section HF24: Wiring Diagram (All Export Models)

Icon for manual Workshop Manual (1969 650cc Twins) Section HF25: Wiring Diagram (All Home Models)

Bonnie Electrical System 2015 (no dip switch, no horn)

Larger Image
Triumph 650 with Pazon electronic ignition wiring diagram (with no dip switch)

Bonnie Electrical System 2015 (with dip switch and horn)

Larger Image
Triumph 650 with Pazon electronic ignition wiring diagram (with dip switch)

Bonnie Electrical System Schematic 2006

Custom wiring diagram for Triumph 650 motorcycle with Pazon electronic ignition upgrade

Original Electrical System Schematic

Wiring diagram for 1969 T120R 650 Bonneville (export market)

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Icon for manual Workshop Manual (1969 650cc Twins) Section H1: Battery Inspection & Maintenance

Parts iconFig.23 Battery Carrier/Oil Tank

Photo icon Battery Carrier/Oil Tank Mounting (2 photos)

Photo icon Battery Carrier (8 photos)

WWW icon " Motobatt (Triumph 650 search)"

Battery Specs

Replacement battery should be a sealed, maintenance-free unit with a minimum 9Ah rating.

For battery carrier dimensions, see Battery Carrier just below.

Possible replacements:

Brand/Part# Height Width Depth Notes
Koyo YTX-12-BS 5-1/8" 5-7/8" 3-5/16" 5 stars, but hard to find
Motobat AGM MB9U 5.3" (13.6cm) 5.2" (13.3cm) 3" (7.6cm) 12v/11aH Popular for British bikes
PowerStar PM9A-BS AGM 5-1/2" 5-1/4" 3.0" 12v/9aH
PowerStar AGM PS-12-BS 5-1/8" 5-7/8" 3-3/8"  
Yasua 5-1/8" 5-7/8" 3-3/8" (Bonnie - June 2018)

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Icon for manual Workshop Manual (1969 650cc Twins) Section H12: Fuses

Use 35 amp British fuse, or 15-17.5 amp US fuse (continuous slow-blow).

When I fabricated my own wiring harness I fused both the positive and negative battery terminals.

Tip!Fusing both battery leads is effectively like having a spare fuse at all times because the positive battery lead can simply be shorted to ground without a fuse.

Once on a trip in the Green Mountains I turned on the ignition switch while coasting down a steep hill in fourth gear. Bang! A big pop and the negative lead fuse blew. No spare fuses with me - I'd left them on the workbench! I shorted together the positive fuse's carrier leads and put the good fuse in the negative lead.

Battery Carrier

Battery carrier inside dimensions: H x W x D.

For more info, jump to Battery Carrier section.

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Icon for manual Workshop Manual (1969 650cc Twins) Section H4: Charging System

Icon for manual Workshop Manual (1969 650cc Twins) Section H7: Alternator & Stator Details

WWW icon John Healy "Lucas Electrical Stator or Rotor Install Guidance" (PDF)

WWW icon Stator Installation

WWW icon J.R.C. Engineering "Lucas Alternator Tips and Hints" Descriptions & test procedures for Lucas alternators, rectifiers, and zenner diodes

Stator Studs

Traps!If stator holes won't line up with the stator studs in the crankcase, or the rotor is off-center in the stator, do not be tempted to adjust the alignment by hammering on the studs. Doing so risks cracking the crankcase. Do any bending with the studs removed and held in a bench vise. (See stator link above).

Rotor Integrity


Icon for manualTriumph Service Bulletin "Loose rotor center or rotor retaining nut"

The way the Lucas rotor is constructed, it's possible for the rotor center to become loose from the outer part holding the magnets. This can be checked by tightening the rotor in place with the stator removed. Gripping the rotor with both hands, turn over the engine in both directions and feel whether there is any slipping movement. Rotors that have become loose cannot be repaired ordinarily, they must be replaced.

Rotor and Stator Clearance

Note that the nuts securing the stator are to be torqued to 30lbs.

When reinstalling the rotor, important to be sure there is sufficient clearance (.008"-.012") all the way around between it and the stator.

Here's a method often cited at the Britbike Forum:

Checking Alternator for Charging

With engine running and lights on, blip the throttle. If intensity of headlight does not increase with revs there is a problem somewhere in the charging system. This can also be verified by connecting a voltmeter across the battery terminals to see if voltage rises when revs do.

The alternator can be checked by connecting either a voltmeter (AC) or a 12 volt bulb across the alternator's disconnected leads and kicking over the engine.

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Wiring Harness


Photo icon Original Wiring Harness - 2005

Photo icon New Repro Wiring Harness - 2006

Photo icon Custom Wiring Harness - 2015

Removing Main Wiring Harness

The selenium rectifier and grounding straps have already been disconnected.

  1. Pull apart bullet connectors to tail light
  2. Free tail light switch
  3. Clamp from spring to brake rod has 5/16", or better, 1/8W nut and slotted bolt head
  4. Disconnect wires (bullets) to contact breakers
  5. Disconnect ignition switch and remove
  6. Remove zenner diode and bracket
  7. If installed, remove bullet connectors to front brake light switch
  8. Remove head light bolts
  9. Pull harness forwards, through fork and out

Routing of Wiring Harnesses

(See original and repro photo sets above)

Main harness

Beneath gas tank. Tied about an inch to the rear from the "Y" (along with clutch cable) to upper tube through space in frame forward of the coils. Then tied again to upper tube just forward of the rear gas tank mount. Passes over the top of the rear loop into the battery area. Photo icon (Photo)

Horn/Dimmer harness (gray plastic)

Passes through the stanchions from the rear Photo icon (Photo)

2006: Eliminated horn and integrated dip switch wiring into the Lucas lighting switch in the headlight shell (see wiring diagram above)

Rear brake switch harness

2006: Tied just above bottom side cover mounting stud and then falls to follows the frame member before looping to the switch.

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Bullet Connectors


WWW icon Bullet connectors, crimp or solder?  High caliber posts, no hollow points.

WWW icon Electrical Work  Advice and techniques for soldering.

Bullet connectors are compact, simple, and generally quite reliable. They sometimes get a bad rap for poor connections due to corrosion, but that issue is likely encountered primarily in very humid climates or coastal areas with salty air.

I recently learned that new bullets on the market are sized for metric wire and not the larger Imperial-sized wire found in original British motorcycle wiring harnesses. Accordingly, a modern bullet will not crimp tightly enough to original wiring, even if it's made for the appropriate number of wire strands. Inserting short wire 'shims' to pad out the larger size of the bullets might be a viable work-around.

Some bullets have two crimping points, one for the wires and one for the insulation. The wire crimp makes the electrical connection and the insulation crimp provides strain relief. Bullets available for British bikes today generally have a crimping point only for the wire.

There's some debate over whether it's best to crimp or solder bullets. Crimping provides a good mechanical attachment, and soldering insures good conduction, so to me it's logical to do both. There is, however, one caveat.

Traps!Unless done with care, soldering can actually reduce reliability.

When solder flows over individual strands of wire they become effectively solid and rigid. Without the flexibility of strands, solid wire is more prone to vibration stress and eventual breakage. Avoid this by using just the smallest amount of solder at the tip of the bullet and only allowing it to flow as far as the mechanical crimp and no further: preserving the strands' ability to absorb vibrations.

Tip!To keep the bullets from falling off the wire while you crimp/solder, strip the wire a wee bit long and splay the protruding ends slightly after inserting the wire into the bullet.

When finished soldering, prevent future corrosion by thoroughly removing traces of flux with a rag and warm water.

Soldering Recommendations

If you have the nervous system of a squirrel you might succeed in using a dual-range soldering gun's low setting for soldering bullets, but something like a 35-watt pencil provides greater control over the process. Either way, use a clean, well-tinned soldering tip for best results.

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Icon for manual Workshop Manual (1969 650cc Twins) Section H17: Twintone Horns & Relay

Icon for manual Workshop Manual (1969 650cc Twins) Section H8: Electric Horn

Parts iconFigure 35 Ign coils, Horn, Rectifier, Zener diode

WWW icon Twin horn relay wiring 1970 T120R

Headlight and Headlight Shell


Icon for manual Workshop Manual (1969 650cc Twins) Section H9: Headlamp

Icon for manual Workshop Manual (1969 650cc Twins) Section H10: Removing/Refitting Headlamp

Photo showing Bonnie's headlight shell wiring:

Photo of Triumph headlight shell wiring

Headlight Reflector/Lense Fixing Clips

The headlight reflector unit (99-0686, or LUCAS 516798) is held in the headlight rim (99-0692, or LUCAS 553248) using fixing wires (99-683, or LUCAS 504665).

WWW icon Classic British Spares: "Installing & Removing Lucas Headlight Wire Clips"

Triumph 650 Lucas headlight and rim photo showing mounting clip orientation

LED/Halogen Headlight Bulb Replacement


WWW icon Head/Tail/Brake Light LED Replacements

WWW icon thread Brett: "LED headlight bulb test: Now with Pictures!"

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Tailight & Stoplight


Icon for manual Workshop Manual (1969 650cc Twins) Section H11: Tail & Stoplamp Unit

Icon for manual Workshop Manual (1969 650cc Twins) Section H16: Stop Lamp Switches

Warning Lights


Icon for manual Workshop Manual (1969 650cc Twins) Section H15: Warning Lamps

Lucas 35710 Light Switch

I've replaced this switch three times on Bonnie. After installing new repro switches I've attempted to recondition the old ones by taking them apart and re-assembling. Never had any success, maybe you're more lucky than me.

The figure below shows the internal connections of the Lucas 35710 (99-0563) light switch in all three positions. See also this chart-style pin-out for the 35710.
Diagram of Lucas 35710 Lighting Switch showing internal electrical connections

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Photo of Triumph ignition switch

Ignition switch


Icon for manual Workshop Manual (1969 650cc Twins) Section H13: Ignition Switch

Icon for manual Workshop Manual (1969 650cc Twins) Section H14: Ignition Cut-Out Button

Traps!Repro editions of the Triumph ignition switch are notoriously prone to failure and the slightest weight of a key fob attached to the key is known to exacerbate the problem - leave your ignition key naked!

An intermittent ignition issue is frequently due to a defective ignition switch. If you're having an ignition problem, one of the first things to do is install a jumper lead from the battery to the coils, thus by-passing the ignition switch.


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Zenner Diode & Selenium Rectifier


Icon for manual Workshop Manual (1969 650cc Twins) Section H5: Zenner Diode Charge Control & Testing

Icon for manual Workshop Manual (1969 650cc Twins) Section H6: Zener Diode Location

The zenner diode is the voltage regulator. When alternator output is too high, it dissipates excess voltage as heat through its heat sink), thus protecting the battery from overcharging, as well as damage to other electrical components.

The selenium rectifier converts the AC alternator output to DC.

Both the selenium rectifier and the zenner diode perform well, but if the pricey zenner diode fails many will replace both it and the rectifier with a single solid-state device, such as a Podtronics or Tympanium.

Selenium rectifier connections:

Photo of Triumph 650 selenium rectifier showing wiring connections Schematic diagram of Triumph 650 selenium rectifier wiring connections


Condensers are only used when running on a points ignition system. They are fitted in parallel with the points and they have two functions to perform.

When the points first start opening, the condenser begins taking on a charge. This draws off the current which might otherwise arc across the small opening points gap. Then, when the points close and the coil's electromagnetic field begins collapsing, the built-up potential across the condenser is discharged through the coil, adding to the energy created in the high tension circuit.

A shorted condenser will create a no-spark condition. An open condenser will cause arcing across the points, pitting them and create misfiring.

To test a condenser with a multimeter, select the thousand-ohm range, place the meter's negative meter against the body of the condenser, and then connect the red meter lead to the positive terminal of the condenser.

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Ignition coils


Icon for manual Workshop Manual (1969 650cc Twins) Section H2: Coil Ignition System

Parts iconFigure 35 Ign coils, Horn, Rectifier, Zener diode

Triumph ignition coil and custom condenser mounting

Ignition Coil Heating Up

On a bike with a points ignition setup it is normal, but not desirable, for one or the other coil to heat up if the ignition switch is left on. This is due to current from the battery energizing the coil through the closed set of points.

If you need to work on the electrical system with the battery connected and the ignition switch in the on position, remove the points cover and slip a piece of paper or plastic between the contacts of the closed points.

EI (electronic ignition) units are programmed to automatically open the coil circuits after a set amount of time if the ignition switch is left on.

Installing Ignition Coils

Note that the head steadies must be installed before installing the ignition coils.

Testing Ignition Coils

Note that just because correct resistance readings are obtained for a coil does not mean that the coil is good. It may be arcing internally or its readings may change when the coil becomes warm.

Resistance readings for 6v coils:

Resistance readings for 12v coils:

Ignition Coil Wiring Connections

With Pazon

Left Coil (DS)

Right Coil (TS) Schematic diagram for Triumph 12v ignition coil wiring connections

With Points and Original Harness

Photo Photo icon

Left coil

Right coil

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Capacitor Ignition


Icon for manual Workshop Manual (1969 650cc Twins) Section H19: Capacitor Ignition

Capacitor ignition substitutes a capacitor - usually a spring-mounted blue "can" - for the battery. This scheme will not work with most Electronic Ignition systems as they require a minimum battery voltage to power them. The capacitor will operate satisfactorily in a points ignition system, but the lighting system will be dim and flickering at idle.

Pazon Ignition


Pazon PDF Installation, timing, and trouble-shooting

Pazon Schematic Diagram

Wiring schematic for Pazon electronic ignition

Pazon - Trouble-Shooting

WWW icon Nick, posting on
  1. "With the ignition on check you have 12 volts or so between the red and white wires on the Pazon and 12 volts or so between the coil supply and the white Pazon wire.
  2. "Place a voltmeter between the Pazon black wire and the white wire, when you switch the ignition on the reading should be about 1 volt or so for a few/ maybe 10 seconds then it should go to 12 volts. (this is the unit switching the coils off under 'stall conditions' to prevent the coil burning out) It will cause a spark at the plugs if the coils are ok.
  3. "If that doesn't work the black box unit is faulty or has been damaged.
  4. "If it worked then connect one side of the sensor with the ignition on and momentarily touch the other sensor lead to its connector, this should also create a spark at the plugs. If it doesn't, check the resistance across the sensor connections, it should be between 120- 250 ohms from memory but sometimes vibration can break the track or the fine sensor winding connections on that plate.

"This will tell you if the box or the sensor is the problem."

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Boyer Ignition Trouble-Shooting


WWW icon "How to Trouble-shoot a Boyer Ignition" Includes good info relating to all EI systems

Podtronics/Tympanium Rectifier/Voltage Regulator Replacements


manual icon Podtronics: Instructions & Diagram

WWW icon Podtronics Home Page

WWW icon Podtronics vs Tympanium

Photo icon Rectifier/Voltage Regulator Installing beneath battery carrier

Both the Podtronics and the Tympanium (as well as Sparx) are solid state devices that replace and perform the functions of the selenium rectifier (rectification of AC alternator output to DC) and the zener diode (voltage regulation).

The Bonnie Ref:
A Hyperlink Junkie's Illustrated Field Guide
to the 1969 Triumph Bonneville


A    B    C    D    E    F    G    H    I    K    L    M    N    O    P    R    S    T    V    W    Y    Z

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adhesive/sealant products
adjust primary chain tension
adjust valve rocker clearance
air cleaners, install
air filters
air screw o-ring
air slide (carb)
align rear wheel
alpha-numeric part# conversion
alternator, check
Amal parts, '69 650s
annealing head gasket
anti-seize compound
applying heat
axle retainers, rings, covers
axle parts, front illus.
axle parts, rear illus.
Banjo bolts, orientation
battery carrier, dimensions
battery carrier, reassemble
battery specs & replacements
Boyer Ignition trouble-shoot
brake light, switch
brake light, switch harness routing
Brake, front
brake, front - adjust
brake, front - center shoes
brake, front - reassembly
brake, front - remove
brake, front - replace
brake pedal, D.S. engine mount, torque stay
brake pedal wear
Brake, rear
brake, rear - center shoes
brake, rear - disassembly
brake, rear - reassembly
brake shoe illus.
brake torque stay
British motorcycle forums
British standard threads
bullet connectors
bushes, replace swinging arm frame
cables, lubricating
cable, speedometer
cable, speedometer - lubrication
cable, tach
cable, tach - lubrication
cables, throttle
camshaft, timing
camshaft bushes, renewing
camplate positions (gearbox)
carburetter cables,air slide,spring
carburetter choke
carburetter, clean idle jet
carburetter, concentric cross-section
carburetter, flooding
carburetter, jet/needle/cut away
carburetter, float bowl leaks
carburetter O-rings
carburettors, specs & settings
carburettors, synchronizing
carburettors, remove as unit
carburettors, trouble-shoot
Carburettors, tune
  Amal tuning links
  high speed
  low speed & sync
Center stand
center stand spring
center stand hardware compatibility
chainguard, replace
chain, see Primary Chain
chain, see Rear Chain
clutch, adjustment
clutch assy, remove
clutch assy, replace
clutch cable
clutch center extractor
clutch center/thrust washer compatibility
clutch drag, causes of
clutch operating mechanism "pops"
clutch pack thickness, Trumph & Aerco
clutch pressure plate adjustment
clutch problems
clutch lever pull too heavy
clutch rod adjustment
coils - see ignition coils
color code, wiring
Colorado Norton Works oil filter adaptor
compatibilities, index
compression, sudden loss of
connecting rods/bolts
contact breaker points gap
crankcase breather, test for
crankcase breather pipe
crankcase oil, change
Crankshaft assy
crankshaft oil seal orientation
crush, cyl head and PRTs
cylinders, re-bore
cylinders, hone
cylinder base bolts, remove
cylinder block & tappet blocks
cylinder block, hone & replace
cylinder block, painting
cylinder block, remove old gasket
Cylinder Head
cylinder head bolts, leaking
cylinder head bolts, re-torque
cylinder head bolts, torquing
cylinder head bolts, torque error
cylinder head, remove old gasket
detonation, pre-ignition
distance pieces, rear axle
electrical, Pazon ignition
electrical, Podtronics
electrical, schematic diagrams
electric wiring color codes
engine compression
engine, installing
engine mounting plate fasteners
engine, removing
engine sprocket, align w duplex sprocket
exhaust system
exhaust pipes, removing
exhaust leaks, sealing
fastener specifications
float and float needle
flywheel, factory changes to
footpegs and brackets, passenger
forums, British motorcycles
Front Fork
front fork, alignment
front fork, dismantle
front fork gaiters
front fork oil
front fork, remove as unit
front fork, remove legs separately
front fork seals, replace
Front wheel
front wheel bearings
front wheel brake
front wheel brake shoes illus.
front wheel fender brackets/stays
fuel lines
fuel lines, plastic and safety
fuel lines, remove carbs with
fuel lines, remove from gas taps
gaiters, front fork
gaskets, remove old
Gas tank
gas tank, paint schemes
gas tank sealers/liners (link)
Gas taps, remove & replace
Gas taps, sealing
gear cluster, install into gearbox
gear oil change
gear oil & yellow metal
gear ratios, 4/5-speeds
gears clash in 1st, avoiding
gears clash in 1st, causes
gears, illus.
gears, 4/5-speed tooth counts
gearbox assy, best way
gearbox assy, 4 ways
gearbox illus.
gearbox problems - resources
gearbox, index camplate & quadrant
gearbox inner cover
gearbox inner cover, remove
gearbox inner cover, replace
gearbox jumps out of gear
gearbox outer cover
gearbox outer cover, remove
gearbox outer cover, replace
gearbox, power transmission illus.
gearbox, remove bearings from casing
gearbox, replace bearings in casing
gearbox, replace inner cover bearings
gearbox, sealing inner/outer covers
gearbox sprocket
gearbox tear-down notes
Gear change mechanism
gearshift camplate positions
General Data T120/TR6
General Shop Info
gudgeon pins, removing
Handlebar grips
handlebars, shock absorber mtg.
handlebars, remove bonded bushes
Head bolts, see Cylinder head bolts
head gasket, anneal & install
headlight bulbs, breaking
headlight bulb LED/Halogen headlight reflector fixing wires
headlight shell wiring diagram
heating cases & other parts
heat insulation, carbs
honing cylinders
horn/dimmer switch harness routing
idle screw o-ring
ignition coils, installing
ignition coils, heating up
ignition coils, testing
ignition coil wiring connections
ignition switch connections
Ignition Timing
index, compatibilities
index, tips
index, traps
indexing gearbox camplate & quadrant
kicking back
kickstart lever tapered pin
kickstart mechanism
kickstart problem, diagnosing
layshaft end play, measuring
layshaft thrust washer locating pegs
Loctite, where to use
Lucas wiring color codes
Lubrication Schedule
main bearings, replacing
main jet
mainshaft bearing, replace in inner cover
mainshaft/layshaft bearings, remove
mainshaft/layshaft bearings, replace
manuals, download
muffler baffles, rattles
nave plate, remove
needle jet
needle jet pin gages
O-Ring Sizing Chart
o-rings, carb to intake manifold
o-ring dimens., PRT seals
o-rings, front fork dust excluder sleeve
o-rings, idle, air screw
o-ring, carb mounting
o-rings, pushrod tubes
o-rings, swinging arm
o-rings, rocker spindles
o-rings, tach gear housing
oil, zinc content
oil breather line
oil change, crankcase
oil filter
oil leaks, drain bolts
oil lines
oil pump
oil pressure switch
oil pressure relief valve
oil seal, crankshaft
Oil tank
Oil tank, '66 defective
oil tank, reinstalling
online resources
paint schemes
parts lists, downloads
parts lists, Hermit's
part numbers, conversion of
parts supplier list
patent plate, replace
Pazon Sure-Fire PDF
Pazon, schem. diag./a>
Pazon, setting timing with
Pazon, trouble-shoot
pilot air screw
pilot jet
pin gage for needle jet
pinion gear removal
pistons, remove
pistons, replace
piston rings, gap
piston rings, install
piston rings, orient.
Podtronics, regulator/rectifier
points, ignition
points, contact breaker gap
powder coating
pressure plate, adjusting
primary chaincase
primary chaincase gasket
primary chaincase oil, change
primary chain. adj.
primary chain, check wear
primary chain wear, photos
pushrods & rocker boxes, replacing
pushrod tubes (PRT)
pushrod tube o-rings
pushrod tube seals
pushrod tube o-ring/seal dimen.
pushrod tube seal "crush"
pushrod tube installation
Rear frame
Rear Chain, adjust slack
rear chain, check wear
rear chain, clean
rear chain, removal
rear chain, replacement
rear chain, lubrication
rear wheel
rear wheel alignment
rear wheel bearings
rear wheel brakes
rear wheel brake shoes, illus.
rear brake shoes, center
rear wheel fender
rear wheel fender brackets
rear wheel, remove
rear wheel, replace
relief valve, oil pressure
remove old gaskets
re-torque head bolts
rings, gap
rings, install
rocker spindles, assemble
rocker spindles, types of
rocker spindle o-rings
Rocker Boxes
rocker box gaskets
rocker box gaskets, lightweight pr mod
rocker boxes, remove
rocker boxes, replace
rocker clearance, adjust
roller bearing, steering neck
rotor, loose center
rotor installation guide
rotor nut, torque
rotor to stator clearance
sealant products
selenium rectifier connections
serial numbers, 1950-1969
serial numbers, 1969-1983
service bulletins
shift linkage (illus.)
shock absorbers, rear
shocks, disassemble/install
side panel
slide (carb)
sludge trap
spark plugs
Speedometer and Tachometer
speedometer cable
speedometer gearbox
speedometer gearbox lube
speedometer gearbox ratios
speedometer problems
sprocket, gearbox - replace
stanchion tubes, compatibility
stanchion tubes, replace
stator installation guide
stator studs
stator to rotor clearance
steering damper
steering head
steering lock
Swinging arm frame
switch, Lucas 35710, connections
switch, ignition
switch, brake light (rear)
tach cable, lubrication
tach drive gearbox, remove
tach drive gear, lubrication
Tappet guide blocks
Thackary spring washers
thread locker
threads, types of
threads, list of left-handed
throttle cables, routing
thrust washer (clutch)
thrust washer (clutch) and GL5
thrust washers (gearbox)
thrust washer (rocker arms)
timing cover, remove (link)
timing, see Ignition timing
tips, index
tires, Dunlop tech ref. (PDF)
tire, front
tire, rear
tools, special
torque settings, head bolts
torque stays, engine
transmission, dismantle
traps, index
trip meter handle won't turn
trouble-shooting, carburation
trouble-shooting, electrical
upgrades (
valve clearance, adjust
valves, replace in head
voltage rectifier/regulator, Podtronics
Warning Lights
wiring, Lucas color codes
wiring diagrams, elec. system
wiring diagram, headlight shell
wiring harness
wiring harness, horn/dimmer switch
wiring harness, rear brake switch
wiring harness, remove (stock)
wiring harness, remove
wiring harness, routing
Workshop manuals, factory
wrench jaw gap sizes
yellow metals & gear oil
zenner diode
zinc, in motor oil

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