The Bonnie Ref

A Hyperlink Junkie's Field Guide to Bonnie (Illustrated)

1969 T120R Ser# NC00125


About Bonnie
Alpha-Numeric part# conversion
Adhesive/sealer products
Air filters
Air cleaners, installing
Align rear wheel
Alternator, checking
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 pedal, D.S. engine mount, torque stay
Brakes, front wheel
Brakes, rear wheel
Brake shoe illustrations
Cables, lubricating
Cable, speedometer
Cable, speedometer - lubrication
Cable, tach
Cable, tach
Cables, throttle
Camshafts, degreeing-in
Carburetors, cables,air slide,spring
Carburetors, cleaning idle jets
Carburetors, jet/needle/cut away
Carburetors, tuning low speed and synchronizing
Center stand
Chain, rear
Clutch assembly, removing
Clutch assembly, replacing
Clutch cable
Clutch operating mechanism "pops"
Compression Tests
Conecting rod big end nuts, TSB-317
Contact breaker points gap
Crankcase breather pipe
Crankcase oil, changing
Cylinder block
Cylinder head
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 and steering head
Front fork seals, replacing
Front fork oil, changing
Front wheel bearings
Front wheel brakes
Front wheel brake shoes
Front wheel fender brackets/stays
Fuel lines, removing connectors from gas taps
Gas tank
Gears, bearings, and bushes illustrated
Gears illustrated
Gearbox assy: Hancox/WSMan/Haynes
Gearbox Assy Advice, BritIron Mailing List
Gearbox, inner cover
Gearbox, outer cover
Gearbox outer cover, remove and replace
Gearbox oil, changing
Gearbox power transmission illustrations
Gearbox, removing bearings from casing
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 shell wiring diagram
Horn/dimmer switch harness routing
Ignition coils, removing
Ignition coils, wiring
Ignition switch, connections
Ignition timing
Issues, history of
Layshaft end play, measuring
Lubrification Schedule
Oil breather line
Oil, changing crankcase oil
Oil lines
Oil filter, Norton fitted
Oils and zinc content
Oil seal, D.S. crankshaft
Oil tank
Oil, pressure relief valve
Parts lists, factory
Parts lists, proprietary
Pazon Sure-Fire PDF
Pazon, schematic diagram
Pazon, setting timing with
Pazon, troubleshooting
Piston rings, removing and replacing
Piston rings, orientation
Points, contact breaker gap
Points, ignition
Powder Coating
Points, contact breaker gap
Points, ignition
Powder Coating
Primary chain adjustment
Primary chaincase oil, changing
Pushrods and pushrod tubes, replacing
Pushrod tubes, seal "crush"
Pushrod tube o-ring/seal setup (Bonnie)
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
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
Shock absorbers, rear
Side panel
Speedometer and Tachometer
Speedometer cable
Speedometer gearbox
Speedometer gearbox lube
Stanchion tubes, replacing
Stator installation guide
Switch, lighting - wiring diagram
Switch, ignition
Switch, brake light (rear)
Tach cable, lubrication
Tach drive gear, lubrication
Tappet guide blocks
Tire, Front
Tire, Rear
Valve clearance, adjusting
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

Supplementary Resources

Proprietary Parts Lists

Factory Parts Lists

Manuals/SB Downloads

WS Manuals/Bulletins

Special Tools

Other Lists

Torque Settings

Bonnie's Back Pages

Parts Sources

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)
  • 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

Return to Index


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

  • Loctite Blue
  • Loctite Anti-Seize Lubricant - head bolts, sparkplugs
  • Hylomar (Newman Tools)
  • Right Stuff (sealing chaincase exit of alternator wires)
  • Wirth caulking (? untried)

Mini Grease Gun

Loading instructions.

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Lubrification Schedule

Crankcase Oil

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 this list 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)
  • Tip the bike and empty through oil tank drain plug
  • Crankcase filter and drain is 13/64" (7/16W is looser)

Oil Filter (Norton fitted)

Change with crankcase oil at 1,000 mile intervals. Filter numbers
  • 06-3371 (/E, /G, /ER)
  • Fram PH6019
  • Wix 57013
  • HD 63810-80A/63782-80

Primary Chaincase

  • Change at 1,000 mile intervals with crankcase oil
  • 350cc 30w non-detergent oil
  • Use 7/16" offset box for primary chain case drain bolt

Gearbox Lube (1st)

  • Change annually
  • 500cc of 90W gearlube (?GP50, never EP or 'hypoid' - latter 'eat bushes')
  • Gearbox oil drain bolt 7/16", use offset boxend

Front Forks

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

Speedometer Gearbox

  • Grease fitting on gearbox annually

Swinging Arm Bushing

  • Grease swinging arm fitting annually

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The Engine

Engine Removal and Installation

Engine Removal

Fig.14 Engine Mounting Plates, Footrests

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. I removed the forward bolt's nut, which faces out and sticks out a bit, and pushed the bolt in, 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.

Used a rope sling to attach the engine to the chain hoist. It worked ok, but not quite as well as during the first time in 2003.

With a slight tension on the sling, I pushed out the front and rear engine mounting studs with a drift. Might be better to remove the bolt first because the second stud is more difficult than removing the first one, and the top stud is easier to get to than the bottom one.

After removing the mounting studs it took a few minutes to get the frame loose from the engine. At this point the bike is on the center stand and the front tire and the frame is slightly off the ground.

When the engine was loose from the mounts, I raised it to come out. Lifted a bit too high, causing the protruding portion of the bottom end casting where the front motor mount stud goes through to become hung up against the engine mtg bracket on the frame. Lowered it a bit and it finally came out.

Note: while not exactly loose, the bottom-most bolt on both sides were not very tight. Should include these in bolt check.

Note: when I removed the rear bolt on the left side, about a quarter of a cup of water came out.

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 chain case 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


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.


** 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 Pressure Relief Valve

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

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Cylinder Block

Fig.5 Cylinder Block, Head, Rocker Boxes

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

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

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.

  • 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

Connecting Rod Big End Nuts

Self-locking nuts on big ends, see Triumph Service Bulletin #317. This is as listed in #7.


Fig.1 Crankshaft, conrods, pistons, rings, camshafts, timing gears


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.


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! -

Piston 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.

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Cylinder Head and Pushrod Tubes

Cylinder head, pushrods

Pushrod tube seals

Bonnie is using Viton o-rings, top and bottom.

As depicted in the '71 USA parts book and Service Bulletin 324 - Pushrod Tube Oil Seals Bonnie's bottom pushrod tube covers are sealed to the tappet blocks using the so-called 'wedding band' with square-sectioned, circular sealing ring.

Currently, sealing rings are sold in both Viton and silicon. Silicon type are available in different thicknesses (see 'crush' below).

This table summarizes push tube o-rings from '69-'71. In 1971, the E1283 top o-ring was a red, high-temperature type. In my experience, they crumbled. Go Viton!

  #7 '70 USA '71 USA
Bottom o-ring E7310 E7310 E7310
Top o-ring E7310 E7310 E1283
Sealing ring E4752

Installing Pushrod Tubes and Cylinder Head

See Service Bulletin 324, Sealing the pushrod tubes.

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 Mr Right Stuff for me. Back to oil and grease.

When installing the head it seems to go better to manuver it into place from the back as opposed to from one side or the other.

Getting the proper amount of "crush" on the pushrod tube seals

When the head is sitting freely (no bolts) on top of the cylinders and pushrod tubes, there should be about 1/16" gap visible. Too much gap and head distortion may occur when head bolts are torqued. Check to see that gap is even all the way around in position as the head bolts 6,7,8,and 9 are installed evenly and lightly finger tight.

Annealling and installing head gasket

According to JH, any surface oxidation left behind by annealing should be removed for a more professional-looking job. It's heavy on my gaskets because I can't really heat the whole gasket cherry red and plunge vertically in deep water. In 2016, the first time I scrubbed with copper cleaner (lots of work); the second time I left the gasket sitting in vinegar overnight and after rinsing off the brown 'fluff' that formed on it, the gasket was 95% bright.

Apply either grease or Permatex copper to both sides of head gasket before installing. I used the Permatex product during both head assemblies in 2016. In the past I've often suspected leakage between the cylinders via the gasket.

Oil Leak, 2014/15/16

In 2014/2015/16 the bike suffered from oil leaks resulting in oil pooling up on the deck above the gearbox.

In 2014/2015 the problem was a leak between the head and the cylinders. I fixed that leak in 2016, but there was another leak, probably at the base of the cylinders because I used a base gasket with a little tear in it. I removed head/cylinders a second time in June and used Baxter (Coventry Spares) gaskets all around: base and rockerbox gaskets with wire.

Should also mention that druing 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.

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.

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.

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Rocker Boxes

Fig.5 Rocker Boxes

(See page B2 in workshop manual)

Replacing Rocker Arm Spindles

Triumph reversed the position of the Thackary spring washers and the thrust washers because the Thackarys could become fowled in the rocker arms. I tried that assembly order once or twice and had trouble fitting the spindles so I went back to the #7 layout. Supposedly, the benefit of putting the Thackarys against the rocker box cases and not the rockers is more oil flow.

See this BritBike Formum Thread.
And this Triumph bulletin.

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.

Rocker Arm 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 more on rocker shaft o-ring size, see this excellent article by Ed Holin.

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

It is not necessary to remove the ignition coils. 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)


Replacing Pushrod Tubes, 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 necessay 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.

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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

Much better to have a little too much clearance than not enough.

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" - feel it and hear it click softly,
  • .002" - just feel it move (half of .004") and no sound (gentle movement)

A two-piece tappet adjuster tool makes it easier to control the stock square-headed adjusters, but the allen head adjusters I installed afterwards are a huge improvement. Much easier using an allen key on the adjusters and a small box-end wrench on the locking nuts.


Things to remember when 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, re-adjust valve clearance after several miles as gaskets will 'crush' further and reduce clearance. Also re-adjust after each re-torquing of the head and re-check it after engine has been sufficiently run in.

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Testing Compression

  • Engine fully warmed up
  • Throttle wide open
  • Five or six kicks

If compression is low, add small amount of oil to the cylinder.

  • If compression improves significantly the cylinder isn't sealing properly: suspect the rings.
  • If compression doesn't improve, suspect leaking valves.
  • In latter case the problem could be a too-tight tappet (slack off tappet adjustment and re-test), but if not then probably valves or valve guides.

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

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Cam Timing

How to Degree In Your Camshaft (PDF).

Ignition timing


Procedure for
setting ignition timing with points.

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


Pazon installation, timing, and trouble-shooting document

Static Timing

Use flywheel locator OR timing pointer 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

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

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The Transmission

Clutch, figure and part listing  /  Primary Chain Case, figure and part listing

Primary Chaincase Lubrication

Oil, or transmission fluid? That is the question.
Primary Chaincase Oil Change Schedule

Primary Chain Adjustment

Remove primary chaincase oil drain bolt. Insert Adjustor D2108. Hold engine against compression with kickstart lever (Service bulletin 1-69, January 27, 1969) and adjust for 3/8" free play through inspection cap on top of primary chain case.

Removing Clutch Assembly

In order to remove the entire clutch assembly it is necessary to also remove the stator, rotor, engine sprocket, and primary chain. See Fig 10 (Clutch) and Fig 11 (Primary Chain Case).


  • Drain chaincase oil and slacken primary chain Primary chain tensioner adjuster
  • Slack off the left side footpeg (3/4" box end) and rear brake adjustor until cover can be removed
  • Remove 3 stator nuts (1/2" deep well socket) and remove stator
    (After digging and scraping out the 'Right Stuff' or whatever I used and removing the wires)
  • Remove Rotor Wheel Puller
  • Loosen engine sprocket (Engine Sprocket Puller)
  • Remove Clutch adjuster nut (9/16")
  • Remove Pressure Plate (Pressure plate adjusting tool)
    WS Manual: 'Put a knife under head of nut to facilitate removal' - well, kind of, once they're already part way out.
  • Lock clutch center and clutch basket (Clutch locking tool)
  • Remove clutch nut (7/8")
  • Loosen clutch center from mainshaft (Clutch center extractor) See below.
  • Remove clutch center, chainwheel, primary chain, and engine sprocket together


Things looked pretty good this January when I tore apart the transmission and gearbox. The primary chain case 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)

Clutch Center Removal


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 (SRM) 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.

Replacing the Clutch Assembly

Re-assemble the clutch assembly:

  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

Re-install the 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
  14. Apply blue loctite and tighten the rotor nut to 30lbs(+)

    Use clutch locking plates when torqueing the rotor nut. If 4th gear and the rear brake are used some of the torque will be absorbed by the clutch shock absorber rubbers and the correct torque will not be obtained (John Healy).

    Also, see
    Lucas Rotor and Stator Installation Guide.

  15. Continue with installation of clutch plates and pressure plates


  • The clutch nut was about the only nut I didn't use loc-tite on here in 2016. I did on the kickstarter rachet nut, inner and outer cover fasteners, the rotor nut, the trap door screws, and the oil junction block nut (from which I also removed the previously installed loc washer and replaced with the proper flat washer).
  • Trap door - in 2016, renewed countersunk screws holding on the trap door. I noticed last year that one of the screw hole's threads were stripped. It's the one at 12 o'clock. I slathered it with blue loc-tite and tightened it down as much as I dared.

  • When replacing the D.S. crankshaft oil seal, the springs face the sprocket according to the WSMan.

    Some say this is an error (Triumphrat vintage forum) and that it should be the other way around because the pressure is from the crank side. Others say WSMan is correct because it would be worse to contaminate engine oil with clutch oil than the other way around. Think I'll stay with the WS Manual.

  • After re-assembling the clutch center and replacing it, the engine sprocket, and the primary chain, be sure to check that the engine sprocket and the clutch basket's sprocket are lined up straight. If not, use shims (70-8038 .010", 70-8039 .015", 71-2660 .030") between the engine sprocket and the crankshaft bearing to align them.

  • When replacing stator, note that the three nuts holding it on should be torqued to 20lb

Replaced 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 Clutch Plates

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

Untried method:

  • Place front tire against a solid wall
  • Tighten adjusters until letting out the clutch stalls the engine is let out.

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 - 1/8" or even a bit more

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

Shifting and Power Transmission Animated

Stills, Rear View    Gear Animation, Rear View

Stills, Front View    Gear Animation, Front View


See Lubrification 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.

Some resources for gearbox problems:

Lunmad websiteGearbox video

Triumph Service Bulletin #329 Third gear ratio and selector forks modifications
John Healy, BritBike post on '69 Bonnie jumping out of second gear
John Healy, article on 4/5-speed gearbox conversion. Inc photos comparing 4- and 5-speed gearbox components.
Triumph Bulletin #8-59 regarding '69 650s jumping out of 2nd/3rd gears.
Troubleshooting Bulletin Gearbox Excerpt showing gearbox modification Third Gear, Upshift Improper
Outer gearbox cover gasket available from LowBrow Some said this would cure gearbox problem, but it didn't.

Outer Gearbox Cover

Fig.9 Gearbox outer cover


Removing outer gearbox cover (WS Man Section D1, page D3)

  • Off the pipes/mufflers
  • Off engine mounting plate (or footrest)
  • Slack clutch cable, remove from hand lever, then gearbox
  • Engage 4th gear (for loosening/tightening nuts later)
  • Remove case screws and domed nuts
  • Depress kickstarter lever slightly - to allow kickstart quadrant to clear inside top of gearbox
  • 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!

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


  • Apply jointing compound
  • Turn kickstart pedal halfway down (its operational stroke)
  • Offer cover to gearbox
  • Check that kickstarter returns

Inner Gearbox Cover

Fig.9 Gearbox inner cover

Replacing inner cover

Be sure to insert the lower forward engine mounting bolt through the inner cover before putting the cover into place. Otherwise, the bolt has to be installed with the head on the outside instead of the inside and the bolt will protrude on the inside, interfering with the oil lines.

Layshaft end play

Although the manual doesn't give any spec, layshaft endplay should be around .005" according to many on the BritBike Forum. Most also agree that it's not very critical as long as there is some endplay.

Two methods for measuring endplay:

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

  • Assemble and bolt on inner cover. Grasp end of layshaft with pliers and move in and out. Measure end play with dial guage and assemble again with suitable shim.

Inside the Gearbox

Gear Cluster Illustration ('69 T120R)

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

Removing/Replacing Bearings in the 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 chain case 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 chain case, 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 retaining pin in the casing with a permanent marker to make it easier to align the matching hole in the thrust washer while installing the mainshaft.

Re-installing Gear Cluster and Timing the Camplate/Quadrant

(Side-by-Side Comparison of WSManual, Herbie Hancox, and Haynes gearbox assembly procedures)

The first time I re-installed 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 re-installed 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.

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

  1. Hancox first assembles the mainshaft into the inner cover, including all the Kick starter parts, and tightens that nut

    As far as I can see, there's no reason why the mainshaft has to be installed in the inner cover before inserting it at the end of the following steps:

  2. Install inner thrust washer, camplate plunger, and camplate (in 1st gear position)
  3. Assemble gears (not low gear yet) on the layshaft and install it into the gearbox and the closed-end needle roller bearing
  4. Put into place the layshaft gear shifter with its roller in the camplate groove
  5. Rest the mainshaft gears in place and put in place the mainshaft's gear shifting fork with its roller engaging the camplate's groove.
  6. Place layshaft low gear in place
  7. Stick thrust washer on the inside cover using grease
  8. Insert the mainshaft (installed in inner cover) through mainshaft gears and high gear bearing
  9. 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:
    1st gear | camplate points out gearcase opening | raise the quadrant to engage camplate teeth

  10. Push on the inner cover

Indexing the Camplate and Quadrant

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

Gearbox Tear-downs

Tear-down 2016

After April and June 2016 teardowns, Bonnie is using the following gearbox components:

  • Gearchange quadrant from Baxter (fixed downshifting problem)
  • Gearchange quadrant plungers from Baxter (outer gearbox cover)
  • Gearchange quadrant plunger springs from Baxter
  • Guide plate from SRM 2015 order
  • Camplate from SRM 2015 order
  • Original camplate rollers (new ones from Baxter on hand)
  • Mainshaft from Baxter
  • Mainshaft ball journal bearing 57-0448 [Ref#15 Fig.8] from Baxter
  • Layshaft closed end needle roller bearing 57-1606 TIMKEN M11121 [Ref#11 Fig.7] from Baxter
  • Various and sundry oil seals, nuts, tab washers, etc. renewed

Tear-down, 2015

Replaced the following components:

  • Mainshaft (SRM)
  • All bushings (except kickstart shaft)
  • Mainshaft and layshaft bearings in gearbox inner cover
  • Layshaft thrust washers
  • Camplate (inner gearbox cover)
  • Camplate rollers
  • Index plunger and spring (MAPCycle yellow dot)
  • Quadrant (inner gearbox cover)
  • Gearchange quadrant plungers (outer gearbox cover)
  • Springs for above
  • Guide plate (outer gearbox cover)
  • Oil seals: mainshaft, inner cover, crankshaft, shift spindle o'ring
  • Sundry tab washers, nuts, cotter pins, keys, etc.

Machining services by North Country Engineering

Return to Index

The Fuel System

Gas tank

Fig.22 Gas tank

When replacing the gas tank, I tighten the rear mount fastener first, and then the two front ones. If the nuts in front are tightened first, it "springs" the rear of the tank upwards.

The threads in Bonnie's frame for the rear tank mount are stripped. At least one of my other two unit 650s had this problem also. A large tie-wrap over the tank's rear mounting tab (bolt and all rubber parts in place) and through the sidecar mounting hole works well, but as per above, tighten the tie-wrap before tightening the nuts on the studs in front.

Bonnie's TS front tank mounting stud came loose once. It was repaired by Leon Goldick of Montreal, who also painted Bonnie's tank.

Gas Taps

When unscrewing the brass fuel line connectors from gas taps, give a light rap on the wrench to break loose the brass connector without turning the gas tap.

When replacing the connectors, don't over-tighten - a few raps with a finger against the wrench will tighten them sufficiently.



Fig.31 Concentric 930  /   John Healy's treatise on Amal carbs - 'Tuning Your Carburetter'

Bushman's Carb Tuning Secrets  /   Amal UK: Rebuilding Mark-1 Concentrics


  • When fitting the banjo bolt and gas pipe to the carburetor, the acute angle (the open end of the 'V' made by the gas pipe) faces forward to the engine)

  • O-rings between carburetors and intake manifold come in thin and thick formats. The thick ones on hand are a little too large and the thin ones are a tiny bit too small. Both still work.

    When using thick rings DO NOT tighten the carburetor mounting nuts all the way or it will bend the carburetor flanges.

    Thick or thin, use grease to fix the o-rings in place for assembly.

  • Idle screw and air screw o-rings (Ref 10 Fig 31) should be replaced every one or two seasons

  • When carburetors are removed it's always a good opportunity to check valve clearances while the access is there

Amal Concentric 930, cross-section

Carburetor parts

  • Needle
    Usually 3 notches, but some have 4. Standard setup is middle notch. Raising the needle enrichens the mixture.

    Needle jets from MAPCycle have four grooves instead of three. When I disassembled during winter 2016 I found the needle on the left carb one groove higher than the one in right carb. I lowered it and they are now both in the second groove down from the top.

  • Needle jet
    Standard needle jet size is .106.

  • Slide (throttle valve) cutaway
    Standard cutaway is 3 1/2. Bigger number = larger cutaway = weaker mixture.

  • Low-speed adjustment screw (pilot air screw)
    When the low-speed air screw is screwed in, the mixture is enriched (Section B11 in Triumph Workshop Manual).

Specs and 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 In = richer2 1/4 - 2 1/21 1/4 - 1 1/2

Re-assembly of cable, spring, air slide, and 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 it's 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 idle 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 drill to pull the dirt out of the jet and downstream:

"Use a #78 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."

Adjusting Low Speed Mixture, Idle Speed, and Synchronizing Carburetters

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

The entire routine for adjusting low speed mixture, idle, and synchronizing:

  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.

Another take on just Synchronizing Carburetters

  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 synchronicity

This is (Jim Bush) Bushman's take:

Synchronizing twin carburetors for idle and slow speed running:

This is one area where there is a lot of misinformation on the process, even in workshop manuals. This will outline the simple methodical professional shop steps to synchronize your twin (or triple) carbs, once all the prep and rebuild work above is completed.

1. Adjust pilot screw to 1 1/2 turns out (turn all the way IN till it stops then count 1 1/2 turns OUT). This assumes that the pilot gas jet has been cleaned as above)

2. Open the throttle to full open and check that each throttle slide is up the maximum amount (i.e. disappears up into the carb body). Adjust the cable adjusters until an equal amount of throttle slide is seen, just peeking through on each carb. It is surprising the number of bikes I have seen with a major difference in the full open position.

3. Once cables are adjusted for full open, fully turn out the throttle adjusting screws (to past were it touches the throttle slide)

4. Insert two 3/16" dia drill bits (or 4" long piece of round bar) into each carb (diameter size should be adjusted to suit the throttle cut away), seating the drill bit under the throttle slide, so that they stick out the end of the carb evenly. Screw in each throttle stop screw until the drill bit "dips" a little, find the happy spot, where the screw just touches the slide. Repeat for the other carb. With a felt pen mark the screw head flat-slot position for reference on each carb body..
5. With the drill bits still in place, perform the fine cable adjustment - by gently opening the throttle and seeing that each drill bit moves at precisely the same moment. Adjust the cable adjusters on the carb or on each cable so that movement is even (should be only - turn each).

6. Start the bike, it will likely idle too high, wait for engine to warm up, then adjust each throttle stop screw down (out) by EXACTLY the same amount, i.e a turn at a time on each, using the felt pen reference mark to make sure the adjustments are same. The idle should be even and by blipping the throttle the pick-up should also be even.

7. The pilot jet air screw may be adjusted at this time, but by very little, no more than to 3/4 turn in either direction. The effective range of adjustment for the pilot jet is 1 turn to 2 1/2 turns. This is where a bit of skill & experience comes into play. By turning one screw a little at a time with the engine running (on both cylinders) you can gauge any difference in running and find the sweet spot. When you hear the engine revs race, you want to turn it back a 1/8 to turn - the sweet spot is not at the extreme. The idle may need to be dropped equally again.

If you have to screw it in all the way or out all the way, then the pilot circuit is still clogged, maybe not completely, but enough to affect the running. Go back and clean the jet.

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 forword edge of the oil tank.

  • Important. When threading the air cleaner adapters onto the carburetors be extremely careful to avoid cross-threading: the adapters are steel and the carburetors are very soft pot metal. Grasp them lightly on either side with finger tips and gently thread them on. If they aren't turning completely freely, STOP!

  • When properly positioned, a) the holes in the air cleaner's chrome cover face down and the solid part faces up, and b) the securing screw and clip are on the inside where they are concealed. Here's a way to get everything aligned properly:
    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 carburetor 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 carburetor

Air Filters

  • Paper, not so good
  • Wire gauze much better (wash out with water and detergent)

Return to Index

Oil Tank

Photo: Battery Box/Oil Tank Mounting  /  Fig.23 Oil tank

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.

Return to Index

Exhaust Pipes and Mufflers

Fig.15 Exhaust System

Remove as one piece whenever possible. Three points: pipe clamp, pipe bracket, and rear hangar.
Nut holding chrome pipe bracket to motor is 5/16W.

Return to Index

Control Cables

Throttle Cables

Lubricating cables

Lube all cables with 10W oil (WS manual calls for the elusive 20W). Taping the spout of an oil squirter can to the cables gives good results.

Cable Routing


New throttle cables. T.S. cable crosses to D.S. through frame and both cables pass through forks on the D.S.


New throttle cables: installed, they measure 42 3/4" (sleeving), or 45" (cable). These are for the new, low handlebars.

T.S. throttle cable crosses to D.S. through space in frame and then both cables pass to left of steering head and NOT through the hole in the headlamp bracket. Seems to give very good slide response.

Neither carburetor has any nipples between them and the cables at this time - perhaps when the new cables have stretched out.


Throttle cables installed without the former cross-over.

Both carburetors now have two nipples between the cables and the carburetors.


Throttle cables originally "crossed over", i.e. the outboard cable on the twistgrip went to the D.S. carburetor.

Throttle Twist Grip

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

  • The screw on the bottom is the friction screw.
  • The screw on the top is the throttle stop - it stops the throttle grip when the slides are all the way up so excessive tension is not placed on the throttle cables.

Clutch Cable


Currently the clutch cable makes an arc and passes through the space between the gas tank and the gas tank bracket on T.S. and resting just on top of the forward oil line acorn nut.

Formally passed to the left hand side through the triangle in the frame beneath tank to rear of coils

Return to Index

Speedo and Tachometer

Fig.33 Speedo and Tach

Tach and speedo rebuilt by Andy Hansen in 2014. Speedometer set to 60,000 miles which is 200 under the actual mileage.

They were reconditioned and came back looking just like new in every respect. Both are still working great after 10,000+ miles (Nov 2016).


Lubricating Tachometer Cable

See speedometer cable below.

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, execess grease will be expelled at cable connection to drive unit.


Rebuilt Winter 2014, Andy Hansenn.

Speedo Cable

  • Speedo cable nut at gearbox end is 9/16"
  • Three ties - 1) down tube, 2) beneath main frame, and (3) swinging arm frame.

Cable Lubrication

Unscrew cable from speedo head and withdraw inner cable. Lubricate with light oil on a rag. No oil on 6-8" closest to speedo head.

Speedo Gearbox

Grease periodically - small greasegun.

Replaced Taiwanese Smith pattern with another Taiwanese Smith Pattern from MAPCycle 2014 when putting rebuilt speedo into service. Have original Smith gearbox on hand.

Return to Index


Fig.18 Handlebar mounting, steering damper  /  Fig.27 Handlebars, control levers, steering damper

Handlebars and their dimensions

Handlebar Shock-Absorber Mounting

For the handlebar shock-absorbing mounting to work, the parts must be installed in the proper order and the hemispherical washers must be installed with the correct orientation.

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

Note If the eyebolt makes contact with the the head lug, see Triumph Service bulletin #306.

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.

Return to Index

Tires and Tubes

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 which dot? White dot, or Yellow dot.

Return to Index

Suspension System

Rear Shock Absorbers



An extra set of hands makes getting those split ring clips at the top a lot easier!

I deviated from the manual in this respect: at the top of the shocks I used a flat washer beneath the head on the outside, and a flat washer between the lock washer and the frame member on the inside.

** However, I'm short a lock washer on the right hand side top.


Don't try to force the mounting bushings between the frame bracket from the rear or from beneath their mounting holes. Instead, install the upper shock bushings by inserting from beneath the spare hole in frame bracket and then sliding them to the rear where the bolt can be inserted from the outside. On Bonnie, the right-hand side slipped right in, while the other side required a few upward taps with the plastic mallet.

Parts #7 shows only one flat washer. The flat washers I got from Waldridge are a pretty good match with the old ones in size and bright finish, so I got rid of the spring washers I'd used last time under the nuts and used flats beneath the bolt heads and the nuts.

Bushings can be pushed off-center it's ok.

Note: I went against #7 illustration and put the nuts out on the bottom shock mounts. This way the end of the bolt doesn't scrape on the brake drum cover.

Front forks and Steering Head

Fig.17 Front Forks

Removing front forks as a unit

Remove as a unit to maintain steering head bearings.

  1. Drain 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 forks... they're 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 forks - oil seals, etc.

  1. Disconnect battery
  2. Drain 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 (Stanchion cap nuts wrench))
  11. Slacken lower yoke pinch bolts
  12. Spread lower yoke slots with chisel or screwdriver
  13. Thread service tool right here into stanchions and drive them free
  14. Remove left and right top fork covers

Dismantling front forks

  1. Remove cork washer and gaiter
  2. Remove spring abutment and spring
  3. Remove dust excluder sleeve with 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 Fork Seals

[Forks seals replaced May 2014/March 2007/May 2003]

  • Replace lower plain washer BEFORE putting new "o-ring" into dust excluder sleeve
  • Built up ends of PVC damping sleeves go DOWN
  • Open side of oil seal goes DOWN
  • Fitting oil seals:
    To prevent damage to edge of seal, place plastic wrap or plastic bag over end of stanchion tube and slide the seal either all the way down on greased plastic film, or on a plastic sled over the greased stanchion tube.

    Slide seal down stanchion, place stanchion in lower fork leg and use it to position seal while pressing seal into place

  • Ends of gaiters with pin holes go DOWN
  • Don't forget to replace fork covers (headlight mounts) before inserting stanchion tubes through lower and upper yokes!

Refitting stanchion tubes

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

Refitting forks to frame

With front forks removed as a unit.

Note: LowBrow has tapered roller bearing conversion kit.

  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)

Steering Head

Refitting without forks

  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)

Return to Index

Front and Rear Axles

Illustration of all front and rear axle parts.

Return to Index

Front Wheel

Fig.19 Front Wheel  /  Wheel Bearing Locking Ring Wrench

Front Wheel Bearings

Photo & Drawing: Front Wheel Axle Parts

Replaced [May 2014 60,000 miles]

Used sealed bearings from MAPCycle.

Replaced [July 2007 36,000 miles]

I disassembled the wheel and re-packed the bearings after cleaning them out with kerosene and compressed air.

The (cupped) grease retainer on the inside of the left-hand side was in backwards I think - the cavity was facing away from the bearing so I put both the retainers back with their cavities facing the bearing the way it appears to be in the parts manual.

Front Wheel Brakes

Front and Rear Wheel Brakeshoe Illustrations

Replaced [May 2014 60,000 miles]

Removing the 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)

Replacing the 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 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 brakes

  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

Front Wheel Fender Brackets/Stays

The front wheel and tire can be removed without disturbing the fender and fender braces if the tire is deflated somewhat

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 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.

Note: The mounting hole for the bottom stay (Ref.4) in the used lower fork leg is threaded, so the bolt must be threaded in and out.

Return to Index

Rear Wheel

Fig.20 Rear Wheel

Rear Wheel and Chainguard

Removing Rear Wheel

Rear wheel must be raised (chain hoist or bike jack) for tire to clear fender when removing.

  1. Remove chain
  2. Loosen rear axle nuts
  3. Remove brake rod
  4. Remove torque stay
  5. Loosen rear bolt for chainguard and raise guard
  6. Pull rear wheel backwards until axle disengages from swing arm
  7. Unbolt two remaining bolts to remove chainguard

Replacing Chainguard

Fig.13 Chain guard

Install the chainguard first (loosely) and then install the wheel.

Putting self-locking nut (14-0702) on bolt (14-0113) fastening the front of the chainguard to the frame can be a huge pain. Try this:

  1. (Bolt 14-0113 must have been in place before fender was installed)
  2. Use tweezers or angled needlenose pliers to place washer over the bolt (Number 7 shows NO washer, though there is one on Bonnie)
  3. Put a "spacer" nut into a 7/16" socket, followed by nut 14-0702
  4. Using an extension as a handle, screw the nut onto the bolt

The bolt head is pretty well held in place by the fender for this operation, it only needs held with a wrench for the final tightening, at which time it is more easily accessed when the side panel is removed.

Alternatively, jam small metal chisel between fender and frame mount to make room for nut, held in place with fingers while threading on nut as above.

Note: installing this bolt and nut has been easier the last few times - perhaps because the stainless fender has become more 'relaxed'.

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. It is much easier to fit the nut and bolt with the passenger peg and mounting plate removed.

Rear Wheel Bearings

Photo & Drawing: Rear Wheel Axle Parts  /  Wheel Bearing Locking Ring Wrench

Replaced [May 2014 60,000 miles]

Used sealed bearings from MAPCycle.

Rear Wheel Brakes

Front and Rear Wheel Brakeshoe Illustrations


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

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


When reassembling the brake, note that:

  • The brake shoe ends with the clips go on the stationary post, not the brake actuation cam.
  • The brake shoes need to go on in the correct "leading" and "trailing" positions, see #7 illustration on page 50.

Replaced May 2014 60,000 miles

With wheel in bench vise, used squashed 2" pipe to apply hard rear brakes while tightening inner hub nuts with socket and crescent wrench.

At first I made it just a bit tight and the gearbox for speedo wanted to turn with the hub. Tighter, still turned. Really tight and the gearbox stayed tight, but wheel was binding.

Wheel still turning (very) stiffly at start of test ride, but easier after 2 miles. After another 5 test ride miles the wheel was turning very freely with no binding.

Rear braking is quite improved and no longer pulses as it did for the past two years.

Rear Wheel Brake Pedal, Brake Rod

Use 1/8W for brake light switch lever.


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:

Rear Wheel Fender Bracket


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


  1. Nut from bolt that fixed 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) (Ref 32 Figure 26) must be installed before putting on the fender.

Rear Chain


  • Best done with master link on the rear sprocket
  • Use ball penn and small drift to dislodge the master link clip and then drive the master link out. The connecting plate drops off and the chain separates.


  • Feed chain back over top of rear sprocket using a chopstick with pointed end inserted in hole of last link
  • Replace master link with chain ends on rear sprocket
  • Chain adjusters are 1/2"


Rear chain (Tsubaki High Quality self-lube) and rear wheel sprocket (MAPCycle) replaced May 2014.

Cleaning chain

Clean and lubricate every 1,000 miles when changing the primary chain case and crankcase oils - works out to 5 to 7 times per season.

  • Pull on an old chain when removing the chain for cleaning
  • Wash chain in kerosene in mom's old aluminum spaghetti pot

Minimize kerosene consumption - keep two 1/2 gallon glass or plastic juice containers - one empty and one full of kerosene. Pour just enough kero to immerse the chain in the cleaning vessel the first few times as you rinse off the worst of the old lubricant and road grit. Each time the kero is dirty, pour it into the empty juice jug. You can use less and less kero as the chain gets cleaner and when there's no more grit the chain is clean.

Put the dirty kerosene aside - all the dirty crud will settle to the bottom before next chain cleaning time. Gently pour off clean and re-use many times this way.

Lubricating chain

Using a pot or pan, immerse clean chain in heavy (summer) chainsaw bar oil overnight. Hang to drip-dry the next day and then wipe lightly with a clean rag before reinstalling.

Pull the clean chain back on with the old chain.

Upon returning from rides, apply bar oil to warm chain with the tip of a gear oil container through the chain inspection hole in the chainguard.

Return to Index

Miscellaneous Frame and Tinwork

Battery and Battery Carrier

Battery Carrier/Oil Tank Photo  /  Fig.23 Battery Carrier/Oil Tank

Battery replacements?


Use 35 amp British fuse, or 15-17.5 amp US fuse (continuous slowblow).

When I rewired with my homemade harness I fused both the positive and negative battery terminals. Effectively this is like having a spare fuse at all times.

While on a trip to the Green Mountains in 2015, I blew a fuse in the middle of nowhere when I turned on the ignition key while coasting down a steep hill in fourth gear. Bang! A big pop and the ignition was dead. No spare fuses with me - they got left at home on the workbench! I recovered by shorting together the fuse carrier leads for positive and putting the good fuse in the negative lead.

Battery Carrier Reassembly

Insert the rubber shock absorbers into the females on the battery carrier and not over the male standoffs on the frame - Murphy's soap helps.


Fig.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 it's 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.

Swinging arm

Fig.13 Swinging Arm, Rear Shocks


When replacing the swinging arm, the large 15/16" nut (Ref 10) and tab washer (Ref 9) go on the DS, and the 7/8" bolt (Ref 8) head goes on the TS.


Was getting a bit of back-and-forth play (grab two loose ends and try to rotate swinging arm left or right) so I replaced the pivot bushes (ref 2) in 2014 (53,010 miles).


Don't be tempted to put the shocks on before the swinging arm because they'll just be in the way.

Like the first time, I had difficulties getting the bolt to thread into the frame on the drive side. But now I know the trick - after trying to push the swing arm this way and that way in an effort to get the threads to take I finally got the idea to use the impact screwdriver with a 9/16 BS or 7/8" socket. Tapped the driver with my plastic mallet while turning slowly and the bolt went right in no sweat!


Assembled 2 sleeve bushes (5/36) and spacer (6/36) with flanged washers and new o-rings, packing with grease as they went

Inserted the bolt, using a small diameter dowel to help line up the spacer and bushes.

Put the nut on loosely and used grease gun to fill until grease bled out both ends. Note\; I wouldn't put much pressure behind the grease because excess will have to be squeezed out the holes when the swing arm is inserted into the frame brackets.

Used plastic mallet (lightly) to position the arm and inserted the bolt. Likewise, played with other end a bit with the mallet and the bolt threaded into the frame bracket on the primary side.

I initially torqued the bolt (8/36) - 7/8" socket - to 50 pounds (the new torque wrench is fun!) but the swing arm was binding slightly so I backed off a tiny bit until it was free.

Use 15/16" socket for the nut (10/36).


Fig.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.

Center Stand

Fig.12 Center stand

Replacing Center Stand Spring

If the stand is off the bike the spring can be levered on using the stand.

If the spring is being replaced when the stand is on the bike, see Installing a Center Stand Spring.

Left/Right passenger footrest brackets

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

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

In addition to 2006 Powdercoating - frame and tinware, the following parts are powdercoated:

  • Oil bottle
  • Cylinder Base
  • Muffler hanger brackets
  • Lower triple tree
  • Front fork lower legs

Not powdercoated:

  • Side panel
  • Chain guard
  • Battery carrier
  • Front fork spring abutments

Return to Index

The Electrical System


Bonnie Electrical System 2015 (no dip switch, no horn)

Larger Image

Bonnie Electrical System 2015 (with dip switch and horn)

Larger Image

Bonnie Electrical System Schematic 2006

Original Electrical System Schematic

Return to Index


Rotor and Stator Installation Guides

Lucas Rotor and Stator Installation Guide and John Healy's Vintage Bike article on same (PDF).

See note above on torqueing rotor nut.

When reinstalling the rotor, important to be sure there is sufficient clearance (.008"-.012") all the way around between it and the stator. One method mentioned at the Britbike Forum is to cut four pieces from a coke can (.008"), fold them over double, position them between the stator and rotor, and then tighten the rotor nut. The pieces should slide out freely.

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.

Wiring Harness

Original Wiring Harness - 2005  /  New Repro Wiring Harness - 2006

Removing Stock 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 forks 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 (cross-reference or photo needed) the top of the rear loop into the battery area. Photo

Horn/Dimmer harness (gray plastic)

Passes through the stanchions from the rear 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.

Notes on 2006 Wiring Harness Replacement

  • British Wiring ~$159
  • Eliminated front brake light (tied down)
  • Eliminated oil pressure switch (cut lead)
  • Re-wired light switch for high/low beam
  • Relocated zenner diode to side panel
  • Turn signal wires not included in loom (really?)
  • Snipped off lead (orange/green?) in headlamp shell was for oil pressure switch
  • Double brown/white lead loose in headlamp shell was for zenner diode beneath headlamp
  • Double brown/blue lead loose near condensers under tank is for the horn
  • Yellow/black ignition wires go to TS ignition coil
  • White/black ignition wires go to DS ignition coil

Headlight Shell

Unused wires in headlight shell (stock harness):

  • Brown/Green (single bullet female connector)
  • Brown/Black (single bullet female connector)
  • White/Brown x 2 (female spade)
  • Brown/Green x 2 (female spade)
  • White x 2 (female spade)
  • Brown x 2 (female spade)

Ignition switch

  • Two Brown/White wires go on one of the switch's twin connectors
  • On the other are two white wires and one Brown/White wire

Selenium Rectifier

Note: Selenium rectifier replaced by Podtronics in 2015

With the (unused) lug on top up and the grounding bolt facing down:

  • White/green stripe lead goes to the clock-wise most terminal
  • The Yellow/green lead goes to the counter-clock-wise most terminal
  • Brown/white lead goes to the center terminal
  • See photos/2004/02/bat2mc/DSCN2698.jpg


Condensers eliminated by Pazon in 2014 (left wiring in place and all original condenser parts, brackets, covers, etc. are retained in inventory.

Had previously (2006, new harness) fabricated a custom bracket and moved condensers from original location to beneath gas tank. See photo below.

Often suspected that Bonnie's habit of firing on only one cylinder after encounters with water (car washes, rain storms) might originate here. Especially when the problem persisted after waterproofing the ignition wires' passageway through the timing case to the points.

Ignition coils

  • Coil clamps go beneath brackets, not over as shown in this photo.
  • Don't over-tighten clamps - ruins coils
  • Use Loctite
  • Coils too far forward chafe the tank
  • Coils too far to rear interfered w by headsteadies

Ignition Coil Replacements 2014

Replaced 12v German ignition coils with 6v TriCor 'High Spark' coils during changeover to Pazon CDI.

Lucas originals and German units both retained in inventory.

Ignition Coil Connections - New Harness (2006)

Left coil

  • White x2 (top) inboard (-) (1 on original coils)
  • White (bottom) inboard (-) (1 on original coils)
  • Black/White x2 outboard (+) (15 on original coils)

Right coil

  • Black/Yellow x2 (red tie) inboard (+) (15 on original coils)
  • White x2 outboard (-) (1 on original coils)

Ignition Coil Connections - Original Harness

Photo of Original Harness Connections

Left coil

  • White x2 on top (-) (1 on original coils)
  • Black/White on bottom (+) (15 on original coils)

Right coil

  • Black/Yellow on top (+) (15 on original coils)
  • White on bottom (-) (1 on original coils)

Ignition Coil Connections - Pazon

Left Coil (DS)

  • Black from module to -
  • Black lead from + to TS coil -

Right Coil (TS)

  • Red from module to +
  • - From + of DS coil

Pazon Ignition

Pazon Sure-Fire PDF

Pazon installation, timing, and trouble-shooting document

Pazon Schematic Diagram

Pazon - Troubleshooting

From Nick, BritBike Forum:

  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 it's 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.'s article on Boyer Trouble-Shooting is very detailed and very complete and includes a lot of valuable information relating to EI systems in general.


Podtronics, Diagram & Instructions

Podtronics home page

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  • Oil leak btwn head and cylinders - dissappeared with re-torque
  • Oil leak from cylinder base - removed head and cylinders and replaced torn base gasket
    Procedures and Completion Times:
    • Remove tank/carbs/exhaust - :13 minutes
    • Remove head steadies/rocker boxes - :43
    • Remove head - :50
    • Remove cylinders - 1:35
    • Clean everything up, inc. old gaskets - 4:00
    • Reassemble everything/adj valves - 2:45
    • Total time: 10:06
  • Staccato exhaust note after adjusting valves - T.S. carb nipple was raised and cocked, giving more throttle to that side
  • Lost footshift lever twice, once in Derby Line and again outside of Ayer's Cliff. Lost the original bolt :( the second time and had to climb the driveway in second gear. Replaced with 1 U.H. 1/4" x 28tpi and lots of blue loctite.


  • Speedo gearbox turned with wheel
    * Use pipe to hold on brake while tightening axel nut
  • Tire rubbing chainguard
  • Idle goes up when throttle rolled forward (D.S. carburetor)
    * Worn out airslides - resleeve carburetors

  • Couldn't get new points OR Pazon to work
    * Problem was a bad spark plug
  • Lost "seating nut" for top lug pinch bolt


First run (2 miles - Chemin Vallieres)

  • High revving

Second run (5 miles - Ayers Cliff)

  • Engine missing severely (electrical)
  • Dead battery

Third run (28 miles - Tyson's Corner)

  • Road grader dust!
  • Running hot?
  • Quite a bit of oil out of fender breather pipe
  • Primary chain case leaking?

Fourth run (50 miles - Sherbrooke)

  • Lost (and found) gearshift lever (again!)
  • Stalls coming to a stop
  • Running hot?
  • Quite a bit of oil out of fender breather pipe
  • Still leaking from primary chain case?

Fifth run (50 miles - Katevale,Magog,Gendron,GVille,Brown's Hill, Ayers Cliff)

  • Lost screw, washer, and clips for exhaust valve inspection caps
  • All rocker box cover nuts and bolts were loose, with one backed right out
  • Head steady nuts were loose
  • Less oil out of fender breather pipe today
  • Seems not to be leaking from primary chain case drain after tightening the bolt


High revving problem was due to such poor condition of o-ring for idle adjustment that the idle screw had no friction and just kept screwing itself in (higher revs) each time i adjusted it. A new o-ring fixed the problem right up.

Although cable friction was not to blame for high-revving, i nevertheless decided to eliminate the cable tie I'd put around upper member beneath gas tank to hold throttle cables as well as clutch cable tight to the frame. Without the tie they take a larger radius arc and seem more "relaxed".

Severe miss and dead battery due to

  • Speedo illumination lead flopping about and shorting out all around the upper triple tree.
  • Shorting out of low tension wires to points due to my not having tightened the small nuts which hold on the leads and the points - one had fallen right off and was lying at the bottom.

I corrected above and timed the engine first using Hancox's static method and then using the strobe. Running really well!


  • Acid spilling from battery
  • Sticky throttle cable
  • Running rough
  • Leaking crankcase oil from hoses
  • Lost right-hand stanchion tube cap
  • Lost gear-shift lever
  • Nearly lost kickstart lever
  • Frame paint disintegrating
  • Never got the "Sleeve nut" #40 on page 55 of #7 parts book. Stock number F8034
  • Integrity of front end? Have the replacement circlip but have not installed it
  • Missing small washers that were between brake switch and chainguard

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About Bonnie

1969 T120R. Serial# NC00125.

Purchased the 28th of June, 2003 from Frank Holmes at Frank's Brit-Barn in New Hampshire. Showing just over 14,000 miles at the time of purchase. Pretty much original condition. Complete except for one Windtone horn.

Frank told me that for some reason the bike was registered as a 1968 instead of a 1969. An explanation for this could be that although it's a 1969 model, it was apparently produced in October of 1968. See serial # prefix 'NC' on this chart.

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