The Bonnie Ref

A Hyperlink Junkie's Illustrated Field Guide

1969 T120R Ser# NC00125

Manual/Tech Bulletin Parts Illustration Special Tool Photograph World Wide Web YouTube Video


alpha-Numeric part# conversion
adhesive/sealer products
adjust primary chain tension
air filters
air cleaners, installing
alternator, checking
align rear wheel
anti-seize compound
axle retainers, rings, and dust covers
axle parts, front illustrated
axle parts, rear illustrated
battery carrier, reassembling
brake light, switch
brake light, switch harness routing
Brake, front
Brake, rear
brake pedal, D.S. engine mount, torque stay
Brake shoe illustrations
cables, lubricating
cable, speedometer
cable, speedometer - lubrication
cable, tach
cable, tach - lubrication
cables, throttle
camshafts, degreeing-in
carburetor cables,air slide,spring
carburetor choke
carburetors, cleaning idle jets
carburetors, flooding
carburetors, high speed tuning
carburetors, jet/needle/cut away
carburetors, low speed tuning & sync
carburetors, mid '69 BSA modification
carburetors, removing as a unit
center stand
chain, rear
clutch assembly, removing
clutch assembly, replacing
clutch cable
clutch thrust washer
clutch operating mechanism "pops"
compression Tests
connecting rods
contact breaker points gap
crankcase breather pipe
crankcase oil, changing
"crush", head and PRTs
cylinder Block & Tappet Blocks
cylinder block, honing and replacing
cylinder block, removing old gasket
Cylinder Head
cylinder head "crush" and PRTs
cylinder head, removing old gasket
cylinder head bolts, leaking
cylinder head bolts, torquing
Electrical system wiring diagrams
electrical, misc.
electrical, Pazon ignition schematic
electrical, Podtronics schematic & instructions
engine, top end
exhaust pipes
footpegs and brackets, passenger
Front Forks
front fork alignment
front fork seals
front fork oil
front wheel bearings
front wheel brakes
front wheel brake shoes
front wheel fender brackets/stays
fuel lines
fuel lines, plastic and safety
fuel lines, removing carbs with
fuel lines, removing connectors from gas taps
gaskets, removing old
Gas Tank
Gas taps, removing & replacing
Gas taps, sealing
gear cluster, installing into gearbox
gears, illustrated
gearbox assembly: three methods
gearbox illustration
gearbox, indexing camplate & quadrant
gearbox, inner cover
gearbox, jumping out of gear
gearbox, outer cover
gearbox, oil change
gearbox, power transmission illustrated
gearbox, removing bearings from casing
gearbox, remove/replace outer cover
gear shifter
General Shop Info
grease gun, mini
handlebars, shock absorber mounting
handlebars, removing bonded bushes
Head bolts, see Cylinder head bolts
headlight bulbs, breaking
headlight bulb LED/Halogen replacements headlight reflector/lense fixing wires
headlight shell wiring diagram
horn/dimmer switch harness routing
ignition coils, installing
ignition coils, replaced (Bonnie)
ignition coils, testing
ignition coil wiring connections
ignition switch connections
Ignition Timing
indexing gearbox camplate & quadrant
Issues, history of
layshaft end play, measuring
layshaft thrust washer locating pegs
Lubrication Schedule
oil & zinc content
oil breather line
oil, changing crankcase
oil filter
oil leaks, drain bolts
oil lines
oil pump
oil pressure switch
oil pressure relief valve
oil seal, D.S. crankshaft
Oil tank
Parts lists, factory
Parts lists, proprietary
Pazon Sure-Fire PDF
Pazon, schematic diagram
Pazon, setting timing with
Pazon, troubleshooting
piston rings, gapping
piston rings, installing
piston rings, orientation
Points Ignition
points, contact breaker gap
powder coating
pressure plate, adjusting
Primary Chaincase
primary chain adjustment
primary chain wear (photos)
primary chaincase oil, changing
pushrods & rockerboxes, replacing
Pushrod Tubes (PRT)
pushrod tube o-rings
pushrod tube seals
pushrod tube o-ring & seal dimensions
pushrod tube seal "crush"
pushrod tube installation
Rings, gapping
Rings, installing
Rings, orientation
Rear frame
rear wheel alignment
rear wheel bearings
rear wheel brakes
rear wheel brake shoes
rear wheel fender
rear Wheel fender brackets
rear wheel, removing
removing old gaskets
rings, removing/replacing
rocker arm spindles
rocker arm spindle o-rings
Rocker Boxes
rocker box gaskets
rocker boxes, remove
rocker boxes, replace
roller bearing conversion for steering neck
rotor installation guide
rotor nut, torqueing
selenium rectifier connections
service bulletins
shock absorbers, rear
side panel
Speedometer and Tachometer
speedometer cable
speedometer gearbox
speedometer gearbox lube
stanchion tubes, replacing
stator installation guide
steering head
switch, lighting - wiring diagram
switch, ignition
switch, brake light (rear)
tach cable, lubrication
tach drive gearbox, removing
tach drive gear, lubrication
Tappet guide blocks
thackary spring washers
tires, Dunlop technical reference (PDF)
tire, front
tire, rear
valve clearance, adjusting
valves, replace in head
Wiring diagrams, electrical system
wiring diagram, headlight shell
wiring harness, horn and dimmer switch
wiring harness, rear brake switch
wiring harness, removing (stock)
wiring harness, replacement in 2006
wiring harness, routing
Workshop manuals, factory

Hermit's Proprietary Lists

Hyperlinked Illustrated Parts Lists

Torque Settings

Special Tools

Other Lists

Links, Articles & Features

Hermit's Classic British MC Links

Hermit's 650 Tech Articles

Bonnie's Back Pages


Parts Sources


Workshop Manuals

Downloads/Other Manuals

Factory Parts Lists

Vintage Fastener Specs

Triumph Service Bulletins

General Shop Info


  • BA - British Association (see Threads, below)
  • BSF - British Standard Fine (see Threads, below)
  • BSC - British Standard Cycle(see Threads, below)
  • BSW - British Standard Whitworth (see Threads, below)
  • CEI - Cycle Engineering Institute - same as British Standard Cycle (BSC)
  • D.S. - Drive Side
  • O.A. - Overall Length
  • L.S. - Left Side
  • L.H. - Left-Hand thread
  • MES - Miniature Edison Socket (Bulb 3W-MES bulb 643)
  • PRT - Pushrod Tube
  • R.S. - Right Side
  • TP - Thread Profile
  • TPI - Threads Per Inch (see Threads, below)
  • T.S. - Timing Side
  • TSB - Triumph Service Bulletin
  • U.H. - Under Head
  • UNC - Unified National Coarse (see Threads, below)
  • UNF - Unified National Fine (see Threads, below)
  • UNEF - Unified National Extra Fine (see Threads, below)

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Alpha-Numeric Part Number Conversion

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Understanding Whitworth BSF AF BA & metric tools (eBay).

SAE threads


  • Unified National Fine
  • Same as American National Fine
  • 60 degree thread angle
  • Unified bolts may/may not have a circular depression on the bolt head, or three interlocked rings on one of the flats


  • Unified Coarse
  • Same as American National Coarse
  • 60 degree thread angle
  • Unified bolts may/may not have a circular depression on the bolt head, or three interlocked rings on one of the flats

British Standard threads


  • British Association
  • Diameters less than 1/4 inch
  • Prefix number (e.g. 12BA) indicates size (lower number=larger)


  • British Standard Cycle/Cycle Engineers Institute/Cycle
  • Three names for the same thread
  • 60 degree thread angle
  • Used mostly in steel fasteners


  • British Standard Fine
  • British automotive industry
  • Finer than UNC, coarser than UNF and BSC
  • 55 degree thread angle
  • Used mostly in aluminum/alloy castings


  • British Standard Whitworth
  • Coarse thread used in aluminum
  • Compatible (same tpi) w American coarse (60 degrees) from 1/4" to 7/16"
  • 55 degree thread angle

English wrenches are stamped with the diameter of the bolt, while American wrenches are stamped with measurement across the flats.

Some charts (like one abovet) list 1/2" and up as 26 TPI, while others list 1/2" and up as 20 TPI, and still others list both 20 and 26 TPI.

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Adhesive/Sealer Products

  • Hylomar (Newman Tools)
  • Loctite blue thread locker
  • Loctite thread sealant
  • Loctite anti-seize Lubricant - head bolts, sparkplugs
  • Permatiex Ultra-Black gasket
  • Right Stuff gasket (sealing chaincase exit of alternator wires)
  • Wirth caulking (? untried)

Mini Grease Gun

Loading instructions.

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Crankcase Oil

Percentage of Zinc Content for Popular Oils
"Tech 101: Zinc in oil and its effects on older engines"

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 convertors. When used in older (classic) car and motorcycle engines, the low-zinc products fail to provide sufficient protection against start-up engine wear.

I used a list showing the percentage of zinc content for popular oils to help select an oil with a higher zinc level for Bonnie. I've been using Shell Rotella 15W-40 since around 2014.

Oil-change at 1,000 mile intervals.

  • Capacity: 6 Imp pints - 7 1/4 US pints - 3 Liters
  • Oil tank filter nut is 1" wrench (remove once a year)
  • I progressively lean bike over on center stand and front wheel while the hot oil drains from the oil tank.
  • Drain bolt beneath crankcase -13/64" is perhaps tighter than 1/2BS (7/16W).

Oil Filter

Colorado Norton Works oil filter adaptor

I fitted Bonnie with a Norton oil filter head in 2011 (43,000 miles). I change the filter and crankcase oil (and primary chaincase oil) at 1,000 mile intervals. Filters I've used with satisfactory results include:

  • Norton 06-3371 (/E, /G, /ER) ($9-16.00Cdn)
  • Wix 57013 (CarQuest, Magog $15.02Cdn) (Amazon, $11.55US)
  • HD 63810-80A/63782-80
  • Fram PH6019 (Amazon, $10.70-$14.53US)

Although the following filters are said to be the same size and have the same thread and general characteristics as the Norton filter, most of them are not easy to find.
  • Crosland 631 or 673 (No listing found)
  • Mann W7 12/70 (No listing found)
  • Jones Filtration 264
  • Fram PH2839 (No listing found)
  • Simca 29932 M
  • Unipart GFE 212
  • AC 5 W
  • NAPA 1352, made by Crosland (No listing found)
  • CarQuest 85352 (white in colour) (No listing found)
  • Champion H101 (No listing found)
  • Wipac CA101 (No listing found)
  • Delco X5 (No listing found)
  • TJ FB2094

In May 2017 I purchased an oil filter adaptor from Colorado Norton Works. The adaptor permits use of filters which are both less expensive and more commonly available. The list of possible replacement filters for use with the adaptor includes:

  • CarQuest 85348 (CarQuest, $8.44Cdn)
  • Wix 51348 (Amazon, 12/$57.70US) )
  • Fram PH3614 (Amazon, $4.26US or 2/$16.99US)
  • Purolator 10241 (Amazon, $8.80-11.80US)
  • NAPA 1348 (Amazon, $8.99US or 12/$73US)
  • AC Delco PF53 (Amazon, $4.47US)

Primary Chaincase Lube

  • Change at 1,000 mile intervals with crankcase oil
  • 350cc 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.

Warning! Tighten the drain bolt very carefully to avoid stripping threads in the soft aluminum case

Gearbox Lube

  • Change annually or at 5,000 mile interval
  • 500cc of 90W GL-4 gearlube (not EP or 'Hypoid' which is bad for bronze bushes)

Draining the Gearbox Oil

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

If the index plunger holder is removed, so is the plunger. The plunger holds the gearchange camplate in position, and if the camplate moves, it may become necessary to re-index the camplate and quadrant.

The small 7/16" plug is at the bottom of a level tube. When replenishing the gearbox oil, the proper level is acheived when oil overflows with the plug removed.

To drain the oil, remove the drain bolt using a 7/16BS (or 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.

Oil Leaking from Drain Bolts

Ideas on preventing oil leaks from crankcase, primary chaincase, and gearbox drain bolts "
How to stop oil and gear box drain plug leaks?".

Front Forks

  • Change annually
  • 200cc 20-30w fork oil.

Speedometer Gearbox

  • Grease fitting on gearbox annually

Swinging Arm Bushing

  • Grease swinging arm fitting annually

The Oil Tank

Fig.23 Oil tank
Battery Carrier/Oil Tank Mounting

Remove 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 waterpump 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.

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The Engine

Fig.2 Crankcase
Fig.14 Engine Mounting Plates, Footrests
Overhaul Manual, Unit 650s '63-'67
TR7RVMan's complete engine teardown advice on TriumphRat forum
Torque wrench settings ->Rods ->Tappets & Cams

Engine Removal and Installation

Engine Removal

Removing engine using chain hoist
Removing engine using floor jack & muscle

The workshop manual says before removing the engine to remove the two bottom bolts holding the front and rear frames together on the left-hand side. The first time I removed the engine, I removed the forward bolt's nut, which faces out and sticks out a bit, and pushed the bolt in and out of the way. I left the rear bolt that threads into the frame because it didn't seem to stick out much. After the engine was removed from the left side as per the manual, I couldn't see why removing either one was necessary, unless it's to drain water out of the frame: later when I removed the left, rear bolt, about a quarter of a cup of water came out.

The first two times I removed the engine (complete except for the rocker boxes) I used a rope sling to attach the engine to the chain hoist to assist in pulling the engine out of the frame. It worked better the first time than the second, when I raised the engine too high and got it hung up on the bracket on the frame. The ropes have to run on both sides of the frame otherwise the engine will be tilted while being guided into position. This can be seen in these photos: Removing engine using rope and chain hoist.

In 2018 I removed/installed the engine (twice!) using a floor jack to support the engine while I lifted it out manually, but only after all the transmission and clutch parts had been removed. Makes a good case for assembling the transmission and gearbox in the frame and not on the bench. Removing engine using floor jack & muscle

However the engine is pulled, it's probably better removing/reinstalling the rear/bottom engine mount stud first because the front/top stud has better access for fiddling around. Before inserting the studs through the frame I put a good dab of grease on their ends. Can't hurt.

Engine Reinstallation

  • T.S. engine mounting plate
    • 2 long slender bolts with nuts go through castings on transmission casing
    • 1 thicker, shorter bolt goes through the frame at the bottom
    • 1 shorty bolt with lock washer and nut
    • Large stud nut
  • D.S. engine mounting plate
    • Easier to put on the driver's footpeg without the chain on.
    • Nuts and bolts are the same as for right side except the two bolts that go through castings in the chaincase are a bit shorter.

    ** Note that the bottom bolts on both sides are supposed to have spacers (#7 page 5/ref 38). They are missing on Bonnie.

  • Forward engine mount (** these fasteners need plating)
    • 2 nuts (3/8W)
    • 2 washers
    • Stud
  • Bottom engine mount
    • 2 nuts (3/8W)
    • 2 washers
    • Stud


I introduced the engine rear end first from the left side. Inserted the front engine mount stud first and then the bottom one. Went up and down a couple of times on the come-along. I drove the stud through from the left-hand side and then used the kickstand as a lever to move the engine to line up the other end.

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Oil lines

Fig.23 Oil Tank & Oil Lines

Removing Oil Lines

The oil pipes at the oil junction block (70-6930) are 5/16".

The first time I removed the oil lines from the oil junction block I found the job difficult - partly because the outer and inner gearbox covers weren't removed, but mostly because I lacked technique.

After loosening the clamps and sliding them out of the way, try these:

  • Gently lock vicegrips onto hose and twist and push and pull
  • With hose in left palm, twist and pull while pushing the hose with fingers of right hand.
  • Place spread tips of locked needlenose vicegrips against the ends of hoses and push using the pliers handle and thumb and fingers of other hand. Be careful not to scrape oil tubes.

    In desperation the first time I used the plastic mallet to rap against the pliers in order to loosen the flexible line. Not a good technique as the WS manual specifically warns against stressing the metal tubes.

Replacing Oil Lines

** The following instructions pertain SPECIFICALLY to Bonnie NC00125.

Correct installation of oil lines is crucial. On Bonnie, connect back (oil tank) to front (oil junction block and front (oil tank) to back (oil junction block).

Or simply, 'Back to front and front to back.' Works either way.

Feed Oil Line

  • The rear oil line (union nut) on oil tank is the feed line
  • It connects to the forward pipe on the oil junction block (Haynes, p.38)
  • So, FF for Forward=Feed

Return Oil Line

  • The front oil line on the oil tank is the return line
  • It connects to the rear pipe on the oil junction block
  • So, RR for Rear=Return

Crankcase Breather

  • Breather Extension Pipe (70-5375 Ref# 39 Fig.2 #7)
  • Attaches to pipe stub (70-2724 Ref# 7 Fig.2 #7) forward of drive sprocket
  • Use 3/8" diameter hose

Breather Tube

  • Passes on 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.

Oil Pump

Fig.3 Oil Pump

Although Triumph made several changes to 650/750 oil pumps, all the pumps are interchangeable (John Healy).

  • 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/ 70-9421 (Scavenge 0.487"/ Feed enlarged to 0.406")
  • 1980 and on: 71-7317 'double check-valve' pump (same 0.487"/ 0.406").

Source: thread "Oil Pump Confusion Unit 650cc SOLVED!":

Oil Pressure Relief Valve

Fig.3 Pressure Relief Valve

Dome nut - 15/16" wrench. Nut behind it - __?__.

Oil Pressure Switch

Fig.6 Timing Cover
TriumphRat forum oil switch thread discussion excerpt.

I have on hand a custom made blanking plug from Walridge for the oil pressure switch that I'm not using on Bonnie. I have never installed it because of concern about whether or not its threads match those in the timing cover. I've read that the casing threads were, at one time, tapered. Putting an untapered plug into a tapered thread hole is said to possibly split the casing. See discussion above.

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Cylinder Block & Tappet Blocks

Fig.5 Cylinder Block
Fig.3 Tappet Guide Blocks

Replacing Tappet Guide Blocks


On his DVD, Hancox says to line up the hole in the blocks with the locator screw hole in the cylinder block, but doing it this way does not guarantee that the holes for the tappets will be parallel to the camshaft. It is a better idea to make the holes square to the camshaft - the screw holes will be lined up if the block is square to the camshaft.

Due to the closeness of the tappet holes it is difficult to get them lined up perfectly - next time place a straight edge on the edge of the holes and it will be easier to get them properly lined up.

I had to have the guide blocks honed by a machinist before the exhaust tappts would ride up and down freely. Only did this after buying another exhaust guide block, so I have a spare.

Replacing Tappets

Important: When replacing the tappets in the exhaust tappet guide block, it is essential that the flats on the exhaust tappets face outward as shown at right in order for them to be lubricated properly.

As per above, new guide blocks may need honing to obtain a proper fit for the tappets.

Replacing Cylinder Block

Removing old gasket material is an annoying job. Using a gasket remover product is probably a much 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.

Before having a shop hone the cylinders, see these links for John Healey's tips on honing and 'dry' ring assembly. It's about getting a good break-in. "Re: L F Harris Pistons/Rings" (honing cylinders) "Dry ring installation"

After cylinders have been honed, wash them with detergent and hot water to remove all abrasive materials left behind. Dry with clean cloth and apply light coat of oil.

  • Dave helped me install the barrels over new rings the first time. Even with four hands it was not easy!
  • The second time (after replacing the tappet guide blocks) I used ring compressors and it was much easier.
  • In 2014 Paul helped me and we just fiddled around until the barrels dropped on.
  • In 2016, again with Paul's help, I went back to using the ring compressors and they worked very well. I tightened the compressors right down until the rings were closed. Then, with the pistons blocked up with wooden rails, we slipped the cylinder block on. The weight of the block easily overcomes the resistance offered by the tightness of the compressors on the rings.

Tightening 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.

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Connecting Rods

Fig.1 Connecting Rods
Triumph Service Bulletin #317 "Self-locking nuts on big ends" (as shown in #7).

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Fig.1 Pistons
Top End Teardown Photos

Removing Pistons

To remove grudgeon pins, heat pistons to around 100C. In 2006 I used way too much heat, so in 2016 I monitered the temperature using the digital laser thermometer. Also in 2016, I first packed snow in plastic bags around the pistons to chill the grudgeon pins before heating the pistons.

In 2016 I was able to push the first pin most of the way out but it wouldn't quite make it all the way. I fashioned a little extractor tool out of a threaded rod, a 3/4" pipe nipple, a short piece of 1/2" copper pipe, and a couple of nuts. (Below, right).

Replacing Pistons

Chill grudgeon pins and, if necessary, heat the pistons. In 2016 I only chilled the grudgeon pins and they slid quite easily through the pistons and the small ends. I thought this was too easy, but the WS-Manual says that's how they should go in.

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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Fig.1 Rings
Triumph Service Bulletin "Piston Ring Replacement"
Triumph Service Bulletin #323 "Piston Ring Gaps"

Gapping Rings

  • WS-Manual says .010-.015"
  • Triumph Service Bulletin #323 "Piston Ring Gaps" updates the manual and calls for .015-.020"
  • Stephan said .012" - 'little more ok but no less'

Installing Rings

Installing rings is pretty straight forward - always from the top and be sure to 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.

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Cylinder Head

Fig.5 Cylinder Head

I think Bonnie's head has been very lightly skimmed, but I'm not sure. I have no way to measure its height, and anyway, published specs for that vary, as probably did the heads themselves.

Annealling and Installing Head Gasket

With only a propane stove or propane torch for heating, I can't heat the entire gasket cherry red to plunge vertically in deep water. Instead, I anneal it section by section. This creates more surface oxidation.

John Healy says that removing surface oxidation left behind by annealing makes for a more professional-looking job. In 2016, the first time I annealed the head gasket, I scrubbed off the oxidation with copper cleaner (lots of work). After the second time I annealed the gasket I let it sit in vinegar overnight. Nearly all the oxidation turned to a brown 'fluff' that rinsed off easily, leaving the gasket 95% bright.

Before installing a head gasket, remove any burring from the headgasket. Burrs, it's said, can become hot spots and cause pre-detonition (pinging).

Apply either grease or Permatex copper to both sides of head gasket before installing. I used the Permatex copper during both head assemblies in 2016. Using a sealing agent will help prevent a) oil leaks, and b) compression leakage between the cylinders.

Oil Leak, 2014/15/16

During 2014/2015 oil was leaking from somewhere on the top end and flowing down the rear of the cylinders, especially the drive side, until it wound up pooling on top of the gearbox.

When I re-assembled after Jan-Mar 2016 top end refresh that leak was gone, but it was replaced by an oil leak from the cylinder base. My last gasket had a bit of a tear on one side, and rather than wait for a new one, I'd used it anyway.

In June (69,575 mi.) I removed the head and cylinders a second time and used Coventry Spares gaskets (from Baxter) for the cylinder head and the rocker boxes (with wire).

Should also note that during first 2016 assembly I used Hypolar on base and rockerbox gaskets. I wouldn't do that again. On the second assembly I used grease as I always had. Another option would be a sealant like Loctite 515.

Note: 3,000 miles later and no leaks to date - May 2017 (72,500).

Anti-Seize Compound

For head bolts and spark plugs I think the anti-seize compound is a good idea. However, when it has been used, it's extremely important to thoroughly clean all threads before reassembly.

A method that works well is to first swab out the bolt holes with Q-tips and then fill them with kerosene. Then run bolts in and out, using a rag to mop up the kero and all the crud as they squeeze out. Repeat using brake cleaner.

Installing Cylinder Head & PRTs

Installing Pushrod Tubes & Cylinder head below.

Torquing Cylinder Head Bolts

Put new head bolts on Bonnie in 2016.

Torque Settings

  • Head bolt #1- 15 pounds - ?
  • Head bolts #2-9 - 18 pounds - 5/16W
  • Rocker box 1/4" bolts - 5 pounds - 3/16W socket
  • Rocker box nuts - 5 pounds - 3/16W or 7/16" box end

Torque figures given are for dry threads. One recommendation is reduce by 20% when wet. On Bonnie this would mean using 15lbs instead of 18, but I confess I do 18 (but not more) even when using anti-seize compound.

Hancox's method is to start with #1 and take them all right down to the end torque. I did that in 2006 and it worked ok, but I feel more confident doing an incremental 'round robin'. That is, tighten bolts 2-9 to 10 pounds, then to 15, and finally to 18 pounds.

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

In 9-8-7-6-5-4-3-2-1 order, back off head bolts by one flat one at a time and re-torque to specs. And always remember to re-adjust valve tappet clearances after re-torquing head bolts.

Cleaning Cylinder Head

If you're ever tempted to try cleaning up a Triumph cylinder head with oven cleaner, think twice lest the head winds up looking this way. It took bead-blasting to remove the resulting corrosion.

There's no substitute for rags and q-tips and kerosene and brake cleaner and elbow grease.

Return to Index

Rocker Boxes

Fig.5 Rocker Boxes

(See page B2 in workshop manual)

Replacing Rocker Arm 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 set of washers (flat and spring) hanging up on the shoulder at that end. Move them around and tap lightly on the end of the spindle with plastic mallet. When everything is lined up it takes only a very light tap.

Thackary Spring Washers

Triumph Service Bulletin #25 "Lubrication - Rocker End, Ball Arm"
BritBike Forum threads: November 2013 and November 2010 and March 2017.

Because the Thackary spring washers could become fowled in the rocker arm notches and therefore block oil flow, Triumph reversed the position of the Thackary spring washers and the flat thrust washers .

Putting the Thackarys against the rocker box cases instead of the rockers is supposed to allow for a greater oil flow. However, the swap should only be made when using rocker shafts that have a lengthwise groove (my Bonnie's don't).

When placing the Thackary washers against the rocker box (the updated parts order) as opposed to against the rockers (the original order), the 3/8" flat washer has to be replaced by a 1/2" flat washer so it will clear the shoulder on the rocker shaft.

I tried the new assembly order once or twice and had trouble fitting the spindles so I went back to the #7 layout, as illustrated here. This ends well because Bonnie's shafts are not grooved.

Starting from TS, the original #7 layout as used by Bonnie:

  • Rockerbox
  • Flat 3/8" thrust washer
  • Thackary spring washer
  • Rocker
  • Flat 1/2" thrust washer
  • Rockerbox center
  • Flat 1/2" thrust washer
  • Rocker
  • Thackary spring washer
  • Flat 1/2" thrust washer
  • Rockerbox

The updated layout (NOT used by Bonnie):

  • Rockerbox
  • Thackary spring washer
  • Flat 1/2" thrust washer
  • Rocker
  • Flat 1/2" thrust washer
  • Rockerbox center
  • Flat 1/2" thrust washer
  • rocker
  • Flat 1/2" thrust washer
  • Thackary spring washer
  • Rockerbox

Rocker Arm Spindle O-Rings

Ed Holin
"What is the correct O ring for the rocker spindles on a '71 Triumph T100R and similar bikes?".
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 - special tool Z111, rocker spindle oil seal compressor, is available. I've never found it effective or helpful.

Rocker Box Gaskets

I've used wire-reinforced (BCS and Walridge) and plain paper (MAPCycle). Now, 2nd assembly 2016, I'm using Coventry Spares wire gaskets (Baxter) for rocker boxes and base gasket. Not sure, but these may be the 'Covseal' gaskets that garner high ratings from many.

Many swear by gaskets which are stainless steel sandwiched between two sheets of paper. Supposed to eliminate leaks: Vintage Triumph Supply, stainless rocker gaskets.

Removing Rocker Boxes

Not strictly necessary to remove the ignition coils, but man, do they ever shine with metal polish and elbow grease! After removing gas tank, torque stays, and the domed nuts and copper washers from the oil lines, gradually release the torque from and remove:

  • (2) 3/8" head bolts and plain washers (5/16W).
  • (3) stud nuts with flat washers (7/16" box-end)
  • (2) 1/4" rocker box bolts and flat washers (7/16 box-end)


Return to Index

Pushrod Tubes (PRT)

Fig.5 Pushrod Tubes

PRT O-Rings

Triumph Service Bulletin #18-69
"PRT O-rings leaking oil - 1969 'B' & 'C' Range"

The table below shows push tube o-rings used between 1969 and 1971. In 1971 the red, high-temperature 71-1283 o-ring was introduced for use on top. Red ones I installed seemed to quickly crumble.

Later, 71-1283 became available in Viton, and that is definitively the way to go. Bonnie uses Viton 71-1283 o-rings top and bottom and, generally speaking, leakage is not a problem.

  #7 '70 USA '71 USA
Bottom o-ring 70-7310 70-7310 7310
Top o-ring 70-7310 70-7310 71-1283
Sealing ring 70-4752

PRT Seals

Triumph Service Bulletin 324
"Sealing the pushrod tubes"

Note that two PRT designs were used between 1968 and 1973 on "B" range 650 machines: 70-9349 ("fabricated"), and 71-2575 ("one piece"). My Bonnie (1969 model year built in Oct 68) has the one-piece part.

Bonnie has been upgraded for PRT seals as shown in the '71 USA parts book and Triumph Service Bulletin 324 Pushrod Tube Oil Seals

The upgrade uses a square-sectioned sealing ring retained by a metal band, the so-called 'wedding band', to seal between the bottoms of the pushrod tubes and the tops of the tappet blocks.

The square-sectioned sealing rings are commonly silicon and available in different thicknesses for adjusting 'crush' (see 'crush' below).

Getting Proper Amount of "Crush" on PRT seals

John Healy, Vintage Bike Magazine "Push Rod Tubes" thread Discussion of PRT 'crush' thread Discussion of PRT sealing rubber protruding

When the head is sitting freely (loose bolts) on top of the cylinders and pushrod tubes with seals and gaskets in place, there should be between .030" and .040" gap - called the 'crush' - between the cylinder head and the head gasket.

Too much crush results in a poor seal and oil leaks, too little risks distorting the head when head bolts are torqued down.

The crush is adjusted by substituting different thicknesses of sealing rings. A thicker sealing ring holds the PRTs and the head higher and increases the crush. A thinner seal decreases 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 tighly 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.

PRT O-Ring & Seal Dimensions

The following dimensions could help in adjusting for proper sealing ring crush.

Head 2.755"
2.785 (Internet forum)
Head Gasket .045-.050
Round O-rings 70-7310 (Buna-n)
71-1283 (Viton)
.987" I.D.(Nom 1") - .103" thick
Square-sectioned sealing rings 71-1190 0.033 (Rabers' spec)
70-3547 0.093" (3/32") (.091 Rabers' spec)
70-4752 0.125" (1/8") (.123 Rabers' spec)
70-1496 0.1875" (3/16") (.177 Rabers' spec)
Pushrod Tubes 70-9349/71-2575

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

Replacing Push Rods and Rocker Boxes

Put dab of grease on bottoms of pushrods. When they are properly seated at bottom you can feel them lifting the tappets as you lift them gently.

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.

Return to Index


Fig.5 Valves
John Healey, Vintage Bike Magazine Where is your valve seat? What you need to know when installing valve seats
Lunmad's Valve Clearance Adjustment Video, YouTube.

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 When checking or adjusting valves with the gas tank on the bike, Lunmad's method makes it much easier to adjust the TS exhaust valve.

Replacing Valves in Head

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.

Adjusting Valve/Tappet Clearance

I tend to err slightly towards extra clearance because it is better to have a bit too much than not quite enough. Too little clearance and the valve may not fully close (and therefore burn) when the engine is hot. Too much leads to 'hammering'.

Sound is an important guide while setting clearance (see 'clicks' below) and when evaluating results, engine running.

Far easier to adjust valves before reinstalling carburetors when they were previously removed. Otherwise, just remove gas tank and air filters.

Coarse adjustment by position

Run adjustors in until they contact the valve stems and then back them off, 1/8 turn for exhaust , and 1/16 turn (1/2 of 1/8) for intake.

Fine adjusting by feel

  • .004" - easy to feel movement and hear somewhat sharp clicking
  • .002" - Can just feel the movement (half of .004") and hear gentle, very muffled clicking is just audible

A two-piece tappet adjuster tool makes it a little easier to control the stock square-headed adjusters, but allen head adjusters proved to be the ultimate improvement. I get the best control using an allen key for the adjusters, and a particular smallish box-end wrench on the locking nuts.

Positioning Valves for Clearance Adjustment

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

  • To adjust DS exhaust tappet (tappet in up position, valve closed), open the TS exhaust valve by positioning the tappet all the way down.
  • To adjust TS exhaust tappet (tappet in up position, valve closed), open the DS exhaust valve by positioning the tappet all the way down.
  • Likewise for the intake tappets.


  • To adjust DS exhaust tappet (tappet in up position, valve closed), open the DS intake valve by positioning the tappet all the way down.
  • To adjust TS exhaust tappet (tappet in up position, valve closed), open the TS intake valve by positioning the tappet all the way down.
  • Likewise for the intake tappets.

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 tappet 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

    Safety Alert
    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 sticking your finger 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:

  • Best to coordinate movement of allen key and wrench to 'drift' towards a new clearance setting rather than loosen the lock nut and try to hold the allen key at the desired position while tightening the nut

  • When loosening and tightening the lock nut and while 'drifting' towards new setting, make all movements in 'slow motion' to obtain the most accuracy

  • The lock nuts don't have to (shouldn't) be torqued down very hard - should be able to loosen them with a smart thump on the wrench handle with a couple of fingers

Adjustment after Retorqueing

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

  1. After running the engine stationary for several minutes in shop
  2. Again after a short ride of several miles
  3. Again after retorqueing the headbolts

Return to Index

Testing Compression

Lunmad's Compression Test Video, YouTube


  • Warm engine
  • Throttle wide open
  • Five or six kicks

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

  • If compression improves significantly the cylinder isn't sealing properly: suspect rings/cylinder bore. 

  • If compression doesn't improve, suspect leaking valves/valve guides.

If valves are suspected, check to ensure no tappets are too tight, preventing valves from closing fully.

Year / Mileage Cylinder Opp Plug In Opp Plug Out
2016 / 68,500mi Left   120
Three heat cycles after top-end job Right   120
    Opp Plug In With Oil
2015 / 68,500mi Left (250F) 60 90
  Right (205F) 90 80
    Opp Plug In Opp Plug Out
2014 / 60,500mi Left na 135
  Right na 145-50
2010 / 43,500mi Left 145 150
  Right 120 150
2006 / (Frank's) Left 165-170 na
  Right 165-170 na
2006 / 28,600mi (fresh after top-end rebuild) Left 135 na
  Right 135 na

Return to Index

Cam Timing

"How to Degree In Your Camshaft" PDF.

Ignition timing

Lunmad's Ignition Timing Video, YouTube.

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

Hermit's Illustrated Ignition Timing with Points.
TR7RVMan's excellent Triumphrat post

Contact Breaker Points Gap: .014-.015-.016"

Setting Ignition Timing with Pazon

Pazon installation, timing, and trouble-shooting

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.

  • Use the Clockwise timing hole in the Pazon circuit board
  • Rotate circuit board until the red dot is under the Clockwise timing hole

Dynamic Timing

Use strobe on either cylinder for dynamic timing

  • Rotating the Pazon plate clockwise causes the strobed timing mark to move counterclockwise (retards timing)

  • Rotating the Pazon plate counterclockwise causes the strobed timing mark to move clockwise (advances timing)

Removing magnetic rotor center

Use Metric M8 bolt threaded into rotor.

Spark Plugs

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

Gap plugs to .025".

Interpretting 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

Return to Index

Exhaust Pipes and Mufflers

Fig.15 Exhaust System

I have Bonnie's original headers with crossover pipe in inventory, but I replaced them with non-crossover types on the bike.

When removing the exhaust header pipes and mufflers, remove them as a unit on each side. Simply remove or loosen the exhaust pipe clamps, the exhaust pipe engine bracket Phillips heads screws, and the muffler hanger bracket bolts.

  • The nuts on the exhaust pipe clamps are 7/16"
  • The nuts on the Phillps head screws holding the exhaust pipes to the chrome brackets are 7/16"
  • The nuts and bolds holding the muffler hanger strap to the muffler brackes are 1/2"
  • The nuts holding the chrome exhaust brackets to the engine are 5/16" BS (removal unnecessary to pull exhaust pipes)

When removing or replacing the exhaust pipes over the exhaust pipe adaptors (spiggots), it's ok to hit them with a plastic mallet as long as you place a thick, folded rag over the pipes and don't go crazy.

Return to Index

The Transmission

Clutch, figure and part listing
Primary Chaincase, figure and part listing 'Unit 650 clutch thrust washer' Clutch thrust washer discussion, inc. types & changes in size. 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

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 Primary chain tension adjuster D2108 into the drain hole.
  3. Hold engine against compression with kickstart lever (Service 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 for (3/8") (1/2").

Note that excess tightness could wreak havoc with crankshaft bearing and/or clutch and/or mainshaft. Too loose and you'll begin hearing strange noises from the primary chaincase, with possibility of damage to stator or casing.

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

Dismantling the Transmission

The clutch assembly, engine sprocket, and primary chain are removed simultaneously after removing the stator and rotor.
Fig 10 (Clutch) and Fig 11 (Primary Chaincase).


  1. Drain chaincase oil and slacken primary chain Primary chain tension adjuster D2108
  2. Slack off the left side footpeg (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 Wheel Puller
  9. (Store rotor AWAY from metal/magnets)
  10. Loosen engine sprocket ( 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 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 clutch locking tool & a 7/8 socket and breaker bar.
    If difficult to remove, use air wrench
  16. Loosen clutch center from mainshaft ( Clutch center extractor) See notes below on removing clutch center xxximage
  17. Remove clutch center, chainwheel, primary chain, and engine sprocket all together

Notes on Dismantling the Transmission


Rotor nut torque was about right, rotor pulled right off by hand. Once again, the 'self-locking' clutch nut not very tight. Will put the blue to it this time. Kickstart ratchet nut was good and tight, not excessively. Engine sprocket, clutch wheel/center all popped off easily with their respective tools.


Things looked pretty good this January when I tore apart the transmission and gearbox. The primary chaincase and clutch assembly were still quite clean. There was some gray (metal) in the gearbox.

Possibly some wear evident:

  • thick washer on DS crankshaft in front of engine sprocket
  • Thrust washer - some 'rings' evident

Things that were kind of loose:

  • Rotor nut - not very tight - (reinstalled with Blue Loc-tite)
  • Rotor stud - finger loose - (reinstalled with Blue Loc-tite torqued to 35lb)
  • Clutch nut - came off fairly easily - (torqued to 50+lb)

Notes on Removing the Clutch Center


In 2016 I began carefully tightenting down the extractor tool and just as I was getting ready to stop and give it a whack with the brass hammer, the center popped off the () mainshaft. Not surprising as the taper on that shaft was very pitted.


The extractor tool only engages the clutch center threads by about a half-inch and in 2015 I stripped its threads.

When the replacement tool from MAPCycle arrived, I applied WD-40 to the clutch center and 'pre-stressed' it with the new extractor for a couple of days.

When it still wouldn't release, I tapped against the inside of the clutch center with an aluminum drift. Then I tried striking the "loaded" extractor tool with a brass hammer. Still nothing moved.

Finally, after researching BritBike Forum, I tried the air wrench. After about 20-30 seconds of gentle hammering at the wrench's lowest setting, the center released from the mainshaft.

That's when I saw that the main shaft/clutch hub key had sheared off length-wise. I also noted that the clutch hub had spun on the mainshaft.

Reassembling the Transmission

Reassemble the Clutch Center

  1. Lay the clutch center flat
  2. Slather it with grease
  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

  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 sprockets so the keyway in the clutch center is at 12 o'clock
  5. Offer the sprockets to the crank and main shafts
  6. It's possible/helpful to tip slightly forward the duplex sprocket and peer down to align the keyway with the key
  7. Tap with plastic mallet if necessary
  8. Install self-locking clutch nut and thick washer to end of mainshaft with blue loctite
  9. Use deep-well socket and plastic mallet to seat the engine sprocket
  10. Torque clutch nut to 50lbs
  11. Install distance piece over crankshaft, chamfer towards sprocket
  12. Install 71-0082 woodruff key and rotor
  13. Install 70-3975 tab washer and 70-3977 shouldered rotor nut
  1. Apply blue loctite and tighten the rotor nut to 30lbs(+)
    When torqueing the rotor nut, be sure to use clutch locking plates to hold the crankshaft and not 4th gear and brake.

    When using 4th gear and the rear brake, part of the applied torque is absorbed by the clutch shock absorber rubbers, resulting in improper rotor nut torque (John Healy,

  2. Continue with installation of clutch plates and pressure plates

A Few Notes

[Bonnie Replacements in 2015]

  • Entire clutch center assembly (center, covers, spyder, rubbers)
  • Clutch hub (old one had turned on mainshft)
  • Gearbox sprocket
  • 58T duplex clutch sprocket
  • Engine sprocket
  • Primary chain
  • Drive chain
  • Clutch plates, steel and friction
  • Thrust washer
  • Crankcase oil seal

Adjusting the Pressure Plate

Triumphrat Forum
Peg's clutch adjustment method.

The pressure plate should be adjusted so that it applies pressure evenly to the clutch plates and also so that it lifts evenly. Using a clutch pressure plate spring adjustment tool, adjust the three pressure plate spring adjustment nuts until the pressure plate is 'wobble-free' as it turns while depressing the kickstarter with the clutch handle held in. Also check to see that the pressure plate is lifting evenly all the way around as the clutch handle is pulled in.

Hope to make a standard with a pointer to assist in this operation the next time.

Pretty sure I over-tightened the clutch adjustment screws in 2014 and probably under-tightened them in 2015 (slipping?).

Clutch Rod Mechanism "Popping"

If the 3-ball clutch rod operation mechanism develops a "pop" when pulling in the clutch lever it means the mechanism is out of its adjustment range. To correct, do this:

  1. Back off cable adjusters until clutch cable is completely slack and the clutch lever (57-2191) inside the outer gearbox cover is at rest
  2. Adjust the clutch rod adjustment pin (57-2159) by turning it out 1/2 turn from contact between it and the clutch rod (57-1736) (not 1 turn as per WS manual)
  3. Re-adjust clutch cable adjusters
  4. Important to leave some slack at the hand lever end of the clutch cable. I think 1/8" would be minimum, I leave Bonnie's quite slack.

Return to Index

The Gearbox

Fig.9 Gearbox outer cover  /  Fig.7 Gearbox inner cover  /  Fig.8 Gearbox, gears and shafts
Triumph Service Bulletin #329 "Third gear ratio and selector forks modifications"
Engine Base for pressing in gearbox DS needle bearing

Shifting and Power Transmission Animated

Stills, Rear View
Gear Animation, Rear View
Stills, Front View
Gear Animation, Front View

Gearbox Lubrication

See Lubrication Schedule

Gear shifter lever

2003, 2006

Twice I failed to tighten the gear shift lever bolt sufficiently and lost the gear shifter in 2003 and in 2008.

In 2003 the lever fell off about a week after being back on the road. I heard it hit the road and went back for it.

In 2006 if fell off about 75 miles into the new season. When I realized it was gone I backtracked and found it about two miles up the road.

Jumping out of Gear

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

When I finally replaced the gear shift quadrant in June of 2016, it fixed the problem straight away. The old quadrant didn't travel 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 old one.

Gearbox Problem Resources

Triumph Service Bulletin #329 "Third gear ratio and selector forks modifications"
Triumph Service Bulletin #8-59 "1969 650s jumping out of 2nd/3rd gears"
Triumph Service Bulletin Troubleshooting excerpt: "Improper Upshift, Third Gear" thread "1969 Bonnie jumping out of second gear" (John Healy)
John Healy, article on 4/5-speed gearbox conversion. Includes photos comparing 4- and 5-speed gearbox components
Lunmad's Gearbox Video

Outer Gearbox Cover

Fig.9 Gearbox outer cover
Outer gearbox cover gasket available from LowBrow Some say a 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.

Removing Outer Gearbox Cover

WS Man Section D1, page D3

  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

    In 2015 I gently tapped long thin knife blade to crack open the outer cover - then tapped cover and wiggled - pried? Bad Boy!

  8. WSMan: "Gearchange pedal should be carefully raised then depressed, to control the release of the plungers and springs from the gearchange quadrant"

Replacing Outer Gearbox Cover

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

Inner Gearbox Cover

Fig.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 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 (1 11/16" socket)

Inspecting the Gearbox & Replacing Bearings

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.

Can't see myself using either of these, but just in case, for future reference: two possible methods to guage end play.

  • Place soft lead solder or Plastiguage (TM) inside of closed end and assemble as usual. After bolting on inner cover, disassemble and measure thickness of solder. Subtract .003-.005" and insert suitable shim behind thrust washer.

  • Assemble and bolt on inner cover. Grasp end of layshaft with pliers, presumably using a protective covering. Move the shaft in and out to measure end play with a dial guage. Reassemble using suitable shim.

Gear Cluster Illustration ('69 T120R)

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

Removing/Replacing Bearings in Gearbox Casing

The inner gearbox casing holds two bearings:

  • Layshaft bearing (57-1606 needle roller 1 1/6" x 7/8" x 3/4")
  • Mainshaft bearing (57-0448 ball journal 1 1/4" x 2 1/2" x 5/8")


I've read that these bearings can be difficult to remove, but in 2016 they both came out very easily without even heating the case.

From the primary chaincase side, I 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 I used the extension to tap on the bearing's top, left, and right hand sides. The bearing moved a little with each blow and it took less than a dozen shots before the bearing exited into the gearbox (and across the shop).

The mainshaft high gear bearing (50-0448) is driven out from the inside of the gearbox. I used a 1/2" drive extension and a 1 1/16" deep well socket. Again, the bearing moved easily with each solid blow and it took about ten hits to remove it entirely.


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

An indespensible trick was to use the old mainshaft as a "stick" to line up the large mainshaft bearing (57-0448) squarly with it's housing in the gearbox casing ( Photo). Once it was started squarly I used a large, heavy drift against the outer race to drive home the bearing ( mainshaft bearing housing and drifts).

The specially shouldered drift I had made for layshaft needle bearing 57-1606 wasn't exactly right to automatically ensure the bearing's correct protrusion (.073-.078") above the gearbox casing, but I went slowly a little bit at a time and it worked out.

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.

The first two times I replaced gearbox bearings I did it 'Hughie Hancox style': a torch and a hammer with drift. In 2018 this method wasn't working for me at all, and after scrapping the DS needle bearing I enlisted the help of Bob St-Cyr. After watching Bob press them in using a 50-ton industrial hydraulic press I am converted - no more bludgeoning bearings for me!

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

Reinstalling Gear Cluster

Side-by-Side Comparison of WSManual, Hughie Hancox, and Haynes gearbox assembly procedures

The first time I reinstalled the gear cluster (2015) I left out the inboard layshaft thrust washer, so I had to take everything out and do it over.

But that was just a start. Altogether I reinstalled the gear cluster five times (and the transmission twice). The first time I put in the cluster, it took just under two hours. The last time it actually took about two minutes.

In 2015 I tried three different techniques for installing the gear cluster. Eventually, I found the WS Manual method (see below) of installing the gear cluster as a unit to be very satisfactory, but I indexed the quadrant with the camplate in 1st gear and not in the neutral between 2nd and 3rd as suggested by the WS Manual (see Indexing Camplate & Quadrant below.

In 2016, after making a dry run of the method Hughie Hancox shows on his DVD, and seeing how easy it could be, I went with that choice. I did not pre-install the mainshaft and kickstarter assy in the inner cover the way Hancox does on the CD. Instead I inserted the mainshaft by itself before putting on the inner cover and then the kickstarter parts.

I can see some advantage to pre-installing mainshaft/inner cover, and I'd be inclined to try it that way next time if for no other reason than to avoid having to torque the kickstarter nut to 45lbs from the right side of the bike while trying to hold the brake on the left side. With pre- assembly, the nut can be torqued while the shaft is held in a vise. (Hoping my old wood-working vise with wood jaws could immobilize the shaft while torquing to 45lbs)!


Juggling, Method One

  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
  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
  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

Juggling, Method Two

  1. Hold layshaft thrustwasher 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 screwdrive 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

Workshop Manual variation, Method Three

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 acheived 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.

Hughie Hancox, Method 4

Hancox first installs the mainshaft and the kick start parts into the inner cover before he inserts the mainshaft through the gear cluster, which he previously assembles according to the steps below. As far as I can see, there's no reason why the mainshaft has to be installed in the inner cover before introducing it through the cluster.

Hancox assembles the gearbox as follows:

  1. Install inner thrust washer, camplate plunger, and camplate (in 1st gear position)
  2. Assemble gears (not low gear yet) on the layshaft and install it into the gearbox and the closed-end needle roller bearing
  3. Put into place the layshaft gear shifter with its roller in the camplate groove
  4. Rest the mainshaft gears in place and put in place the mainshaft's gear shifting fork with its roller engaging the camplate's groove.
  5. Place layshaft low gear in place
  6. Stick thrust washer on the inside cover using grease
  7. Insert the mainshaft, previously installed in inner cover (or not), through mainshaft gears and high gear bearing
  8. Index the quadrant in 1st gear

    This was my only hiccup in 2016. I thought I remembered HH indexing the camplate/quadrant by letting the quadrant drop. Actually, in first gear the camplate is raised slightly from the full-down position, just as I did last year. Once I reviewed the DVD I saw my error and things went smoothly from there. So, remember:
    1. 1st gear (camplate pointing out gearcase opening)
    2. Raise the quadrant to engage camplate teeth

  9. Push on the inner cover

Inportant Note: Before replacing the gearbox inner cover be sure you've installed the lower forward engine mounting bolt in the cover from the back. Otherwise you'll have to install the bolt with head to the outside, leaving the nut and bolt protruding on the inside where it will interfere with the oil lines.

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.

Indexing the Camplate & Quadrant & Replacing the Inner Cover

The Camplate and Quadrant can be indexed in a variety of positions:

  • When indexing with the camplate in 1st gear position, the quadrant is raised from the down position to mesh with teeth on camplate
  • When indexing with the camplate in 4th gear position, the quadrant is dropped from the up position to mesh with teeth on camplate
  • When indexing with the camplate between 2nd and 3rd gears, the quadrant is held 'level' to mesh with teeth on camplate

For more details, including photos and illustrations, see "Gear Selection Quadrant & Camplate Indexing"

Gearbox Tear-down Notes

Tear-down 2018

Never thought I'd be back here so soon, but here I am going through the gearbox again after finding a significant quantity of bronze'paste' inside.