Belt Primary Drives

Not open for further replies.
Nov 21, 2005
how many of us have them?

how would you grade your manufacturer?


TIPS for those who have yet to convert to the belt?

Thank you for helping us less fortunate!
Less fortunate?? I wonder. This might become a very interesting thread.

I have toyed with the idea of using a belt primary for years, but when weighing the cost vs. benefit, have a hard time justifying it. For a racer or a balls-to-the-wall hot rod street bike, then maybe.

Each time I look at this option I find other ways I'd rather spend the money. The pros are
1) Light weight
2) No oil leaking from the primary
3) Different primary gear ratio
4) ????

The cons are
1) Require careful set up to avoid ruining the belt
2) Cost
3) Availability of replacement parts in the future.
4) ??

Somebody convince me I need one.
I have a belt drive in my cafe racer commando, I bought it from Norvil and consider the price to be reasonable. I was going to have to replace the chain and several other clutch components anyway so this seemed like a good way to go. I also used a damaged and otherwise unuseable primary drive cover with judicious vent holes added where the damage was, so all in all I have to say that it was a good move under these specific circumstances, but I cannot notice any performance or smoothness advantage over my roadster which is in standard trim and doubt that it is worth doing unless there are other considerations.
For what it's worth I decided the cost would be outweighed by no leaks, improved clutch action and supposed smoother running. Well without exception (almost) the Norvil 30mm kit has been perfect. Leaks are cured except for oil coming down the sleeve gear which pools at the front (low point) of the primary. I "O" ringed the pushrod as a precaution and that stays dry. With a new non distorted spring the clutch releases so cleanly it has to be experienced to be believed as does the 2 finger clutch action (1 finger with an old Dommie actuating arm but less throw).
The only downside I can see is after 10k miles the teeth on the Surflex plates are worn to sharp points and I don't recall seeing any signs of this when the chain and ATF was in use. Maybe I'm just hard on the clutch and if the plates were wearing before the belt drive I never noticed it. Since ATF should not be anywhere near the plates in qty I can't believe it was lubing the clutch centre?

The only slight issue I have is running the belt loose when's noisy and clatters at idle. Being of the doubting school I first set it up with minimal play but when that clutch drum heated up the belt was tight as a bowstring and you could forget clutch release. Still when it's hot and properly adjusted with 30mm min deflection it's fine.

I know others have had problems with belts but I wouldn't go back to chain. The basic Norvil kit fitted my 72-74 Commando hybrid perfectly and the only essential check to make is be sure that the top and bottom gearbox stud holes are not too sloppy or you will need to add an adjuster to the primary side. Mine was OK and without the front pulley side plates the belt centered itself with no sign of walking off the pulley. I also geared up the drive with a 35/72 combination for a 4.114 overall.
Belt primary

Last year for Xmas I gave myself a primary belt drive from
clubman racing, (just under $400). Installation was a little tricky as I needed to take a file to the woodruff key in the crankshaft to get a proper fit for the front pulley. Also, the belt was somewhat shorter than the chain which meant the tranny had to be tilted almost as far as it would go forward. This caused the next problem which was that the screws that held the steel plate in the bottom of the aluminum clutch basket and protruded through the back would now rub on the circular bossed up area of the inner primary (cured by grinding off the extra length). The kit changed the primary gear ratio alot, so I ended up having to drop two teeth on the front sprocket. I followed Dyno Daves advice and vented by removing the tin plates from the inner cover. I worried about potential water build up from rain or washing so I drilled a small hole (tapable, therefore repairable) in the lowest spot of the outer primary.
Everything seems to be working great, and improvement to the clutch action made it all worth while.

justa thought,
The only one to buy! Tony Hayward in Conwy Wales, polypropylene toothed belt steel braced super strong runs in ATF which allows alternator cooling without butchering primary cover, also no problems with chafing against guide plates wearing away side of belt. Well made, comes with alloy clutch basket & engine sprocket, no I am not Tony Hayward!
I too plugged the chain oiler feed on my Commando's,although it did keep a nice coating of oil on the rear wheel chrome!.I use Dupont white lithium grease from an aerosol can,available from Lowes in the USA,don't know about Oz.,the stuff is the "bee's knee's",even after a hard run the grease stays on the chain,in 40+ years of riding and wrenching I have not found a better product for chain maintenance.Ride safely.James
Well - I splashed out and bought an RGM belt kit (liked the idea of the oil tolerant belt) and after 6 months i can report that i expect that it will work much better when i get inspired and finally fit it!!
Not open for further replies.