1995 Thunderdird Modifed for 100hp

TRIUMPH T140D - 5 week Restoration
TRIUMPH RIGIDS from 1950 - 1951


We are located in sunny WHITE ROCK, BC, CANADA

Contact Jim Bush by email

Phone 604-535-5800







TRIUMPH T140 Upgrades:

The following outlines work and upgrades I completed on my 1979 T140D Bonneville Special. It has transformed it into a thoroughly enjoyable daily rider.

1. Triumph 7 Plate Clutch Fix: One of the  best upgrades I have done on my Triumph T140D Special Bonneville during the recent restoration was to install a 7 Plate Clutch Kit from LP Williams - mail order  from the UK (web address is ). List is £51 and landed here, tax paid was under $150CDN. The  kit comprises 7 bonded friction plates, modern design & materials, with an extra plain steel plate.
                The installation is straight forward, remove primary cover (collect oil), remove clutch centre by unscrewing the three slot head spring adjusters (special tool req’d).  Remove the clutch pack (plates) and separate the plain steel plates for cleaning. The clutch drum and centre should be closely inspected for notches. Minor notching can be dressed with a file, but deep notching requires replacement of the parts. The steel plates should also be inspected for burred /worn tangs. These can be dressed with a file, but  in extreme cases should be replaced. The new clutch pack installs easily—friction plate in first (lightly oiled in engine oil), then the steel plate and so on. The thickness of the new 7 plate kit matches the original spec for the Triumph 6 plates. Remember to balance the spring adjusters to allow the clutch centre to rotate evenly—need a 2nd pair  of hands to operate the kick starter whilst the clutch springs are individually adjusted.
                At this time you may want to replace the springs, and the clutch cable, and remember to order a primary chain case gasket. The rubber shock absorber  may also need attention as these do deteriorate with age and use.—the tell tail is gooey black greasy looking film on the clutch centre. The replacement process for these  does require some special tools and skill.
                The difference in operation is significant. Firstly, the plates do not stick after it has been sitting—start the bike and nock it into first with a snick—no graunching rasping or lurching.  On the road, gear changes are easy as the clutch disengages with a moderate pull on the lever and now you are able to easily pop it into neutral when you come to a stop.

2. HIGHER  FINAL DRIVE GEARING. This can be accomplished in several ways. Change the gearbox sprocket from stock 20t to a 21t  and/or go to a smaller sprocket on the rear wheel. On my T140D Special, I did both, which is quite radical. To install  a 21t on the front, it will involve milling the engine cases behind the clutch cover plate with 21 notches so the sprocket can be installed and removed at a later date. I did this with the cases on the bench, but it could also be done in situ. The sprocket on the rear wheel I also changed to the smallest I could find – a 45 (stock was 47).


I am very pleased with the result – at 2800rpm it is doing 50mph, which makes the bike feel very lazy and smooth, bags of torque and a most relaxed ride. At 70mph highway speed it is doing 3800rpm, very smooth, little vibration and on the cusp of the torque curve/power band when wanting to accelerate. The T140D takes on the personality of a Norton Commando, with some extra oommph!

3: PERFORMANCE (Torque) CAMS. It is well known that the T140’s used a racing cam on the inlet and a mild cam on the exhaust for noise/emission reasons. I replaced both of these with a pair of Mega Cycle 510-05 – these are street cams, designed to increase torque at low-mid range, whilst keeping a good top end. These are pricey at $550/pr but the result speaks for itself.  There are quite a few choices of cams out there – I would avoid race cams as you lose the low –mid performance, which is what makes these bikes enjoyable.


4: HIGHER COMPRESSION: When upgrading cams it is good to consider also increasing the compression ratio. The T140’s come with a low 7.9 compression, whilst the 650’s came with 9:1. I found a set of Powermax (1980’s old stock) high compression pistons on Ebay and these have been installed. Compression ratio is 10.5:1 and the domes on the pistons look quite impressive, when compared to stock. The crank will need to be balanced to the new pistion weigths, I had this done by CINCINATI BALANCING in Port Kells - to 84%. This has proved spot on - 60-70mph cruising is vibe free.

My motor now feels incredibly strong, with bags of torque and nice crisp mid to top end. The T140D also benefits from having a Lucas Rita ignition and Amal MkII Carbs in the best cyclinder head Triumph ever produced.

5: UPGRADED MAIN BALL BEARING. The later Triumphs (including T120’s) use a metric 6306 main ball bearing on the timing side (part# 70-3835). Whilst this is generally a good choice of bearing, there is a high load version available - called the 306. The benefit here is three extra balls to share the load – these have 11 balls instead of the usual 8. It is important to get the proper C3 clearance spec on these. These are also readily available from most local bearing houses. These are also direct replacements for the ball bearing on the Norton 750’s instead of going to the really expensive superblend bearing.


6: REARSETS AND FOLDING KICKSTARTER. I have also installed a set of HYDE REARSETS and a T160 Folding Kitstart lever, along with some 2" rise EURO Handlebars. This drastically changes the riding position into some thing more comfortable. The pegs are a tad high, but I can live with that - no more dragging the toe of boot on the tarmack. The slight forward lean on the handlebar means you are sitting on your thighs, rather than your tailbone


I am not a believer in trying to overdo upgrading these 30 year old engines to match modern performance standards, the result is often limited reliability and a broken engine. On a recent Top Gear TV Show, they compared a 70’s E Type Jaguar and an Astin Martin DB5, (both very high end performance cars of their time) to a current Honda Accord Japo Box. The Honda was a clear winner and who would have thought that – an E Type, surely that is a rocket. My point here is modifications and upgrades should be geared to improving reliability and rideability. If you really want your bike to go fast, handle and stop well, your dollars are better spent on a modern bike that comes with over  100hp, great handling and real brakes...right out of the box.