Primary Belt Drive Pros and Cons?

I am wanting to fit a RGM belt drive primary side to my straight low mileage '73 850. Researched as best I can, am ok about fit up and alignment, would like some honest feed back on advantages/disadvantages from members who have run them long term
Regards Mike

Pros are the clutch works much better dry. It doesn't slip and it dissengages cleaner so neutral is easier to find.
No oil to leak.
A properly set up belt will last longer than a chain.
Quieter.

Cons with the RGM drive are the clutch drum usually needs to have 20 or 30 thousanths removed from the outboard end of the splines so there is enough room between the circlip and the splines to allow the diaphram spring to go slightly concave and apply correct pressure to the pressure plate. If you make the clutch stack thicker so the diaphram spring does not need to go concave you will be rewarded with a heavier than necessary clutch pull and more clutch drag.

Sometimes with the RGM front pulley the center will be a little too large and the backside of the pully will contact the crank seal and destroy it. I have had to exchange pulleys or use shim stock under the pully to keep it from going on too far from time to time. Jim

thanks Jim, sounds like the pro's win, how long have you had out of yours once you got it sorted?

On my main ride around 76,000 miles. 73,000 miles on the first belt.
I also have two other Nortons with RGM drives and low miles and have installed several for other people. Jim

Yes, JIm ONLY got 73,000 out of the first belt. Most commando's would never need to change the belt.

It took two motors to wear out 1 belt. And boy was it petrified.
I turned 100,000 miles this summer since I assembled my bike from scrounged parts in 1981. Jim

thanks guys, at my age I might not last the life of the belt as well!!!
Is the issue of front pulley fit up and clutch hub machining a common problem, I sourced some old threads that all seem to have had issues, like belt to short making the clutch cluster having to come way forward(gearbox movement) and then touching the inside of the case. Rob at RGM assures me the 890mm belt is the go these days as opposed to the 920mm belt, any info would be appreciated as I see it does'nt 'just slide into place' !!!
Regards Mike

I would say I have had to machine most if not all of the drums I have installed. I don't even check them first anymore. I just chuck them in the lathe and remove .020 and find that usually does the trick.

I have only seen problems with the front sprocket 2 or 3 times. Ran into one earlier this summer and fixed it with .002 SS shim stock cut to fit in the taper. Jim

As I remember the RGM belt makes the primary a bit larger (like a larger sprocket) in the rear end. How does the Norvil belt drive compare? You can get any ratio with the Norvil one as I understand.

Dave
69S

Pro, less mass and once belt tension set can weld the tranny in place as never needs changing even to remove and replace belts. Provides artistic expression opportunity in decorative only venting cut outs.

Con. much get tranny rebuilt to spec or clutch wobble a chain can take will run a belt right off to ruin. Only the past Dreer supplied Haywood type drive is a plug and play kit, and so it seems is Steve Maney's too. It ain't Norton no more.

I've run both 920 and 890 and find the 890 requires too much full forward position of trany in cradle slots for my sloppy tastes. Jim can get away with such mileage because he hardly strains on his leisurely riding : )

I have not checked recently but you used to be able to get RGM drives with different ratios. I never used them.

The Norvil drive definately has several ratios available. Matt uses one that is similar to the stock ratio.

Going larger on the engine sprocket does wonders for transmission longevity but you end up needing a smaller rear drive sprocket on the trans. I always used a 19 tooth which comes out about the same as a 21 with the stock primary drive. Jim

[quote="hobotI've run both 920 and 890 and find the 890 requires too much full forward position of trany in cradle slots for my sloppy tastes. Jim can get away with such mileage because he hardly strains on his leisurely riding : )[/quote]

You want to see the speeding ticket I got on the way home from LOP.

That's what I didn't like about the RGM. It turns into a 21 tooth rear with my 19 tooth sprocket. I ride around on these country roads and never hit the highways, so I'm always between 50 and at most 60, and a 21 tooth rear would make it even worse to lug. I got a message from Roger that the RGM unit turns it into a 21 tooth rear, not what I want, that's why I went to look at Les' drive, he has any ratio you like as I see, but I'd like a review on it before I spread his palms with loot.

Dave
69S

I have probably installed about as many Norvil drives as I have RGM drives, just not on my own bikes. I have found them to be pretty much plug and play.
You could always use a 17 or 18 tooth sprocket. Just a little hard to find in a 530 width. Easy if you want to drop to a 520 chain.

Comnoz, I'm not clear on what you have to machine on the clutch drum. Are you making the circlip slot slightly looser or machining the very outside of the clutch drum to slim the whole assembly down. If you are widening the circlip slot to give greater stack clearance wouldn't some slimmed down steel plates have the same effect?

Thanks guys, you gotta love this forum, I have read years older links about the gearing problem, I guess a selection of crankshaft pulleys or gearbox sprockets whould be the go until it suited my needs. UK is a lot like NZ with its roading, not the huge open highways like the US, plenty of hills and twisty secondary roads down this part of the world.
Keep up the info
Regards Mike

Dave M, The problem I have seen is the distance between the snap ring groove and the outer end of the spines [that engage the steel plates] is the same thickness as the diaphram spring. That means the diaphram will fit when it is flat but when it trys to go concave it cant because the end of the splines prevent it from being able to flex inward.

The area marked in red needs to be machined back about .020 so the diaphram can flex inward to a concave shape.

My Norvil belt drive primary is indeed "plug and play", as is the case of four other Commando friends with Norvils.

Hobot, curious as to where or how you got the information that this well known, multi year available belt drive was not plug and play. Or perhaps tell us what common problems you are aware of not making it plug and play?

Thanks

Duh 1>3<. your chip is showing, I was just re-phrasing what the initial posts in this subject line said, problems with listed kits as supplied. I did not pick on Norvil products.

Once the belt clutch basket is sorted what difference does it make whose crank pulley and ratio is fitted? This is the big down side for final belt drives, switching ratios for different race conditions, not a big deal for street use. Each significant pulley change needs another belt T count. Buell racers are chain final because of this.

You want to see the speeding ticket I got on the way home from LOP.

Click to expand...

Just jerking your chain, err a, belt on belt drive line JIm. You're solid gold where ever poked and some local county knows it too now : ) Would like to know what the radar claimed you were doing and how much they want for it.
Still reflecting on the couple decades racing briefing you let me in on. One of the over the crest hazards I've a reflex to brake hard for now is running up on a cop going up the far climb out, in my lane, at over twice legal speed. So far
their rear view mirror stayed aimed downward while i seriously squealed down before noticed. I've been in jail over speeding/no Dr. Lic. so don't get rushed on real travel, just go with the faster flow and hang back form everything.

One thing I found out with a good wind screen is the sense of wind speed and noise is reduced/gone, so I must watch speedo for tickets and corner entry speed.
Once used to it not a big deal but going from naked to shielded the first time sure was.

They got me at 83 in a 65 about 100 yards into Colorado. $165.00 Good thing they didn't catch me a few miles earlier as I was slowing down for the CHP. Just not soon enough.