RGM Belt drive issues (2018)

Kevin McDermott

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Jul 24, 2018
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I'm currently attempting to successfully install a RGM belt drive to my Mk3. The kits installed and I'm happy with the tension of the belt, the primary is reassembled And I'm ready to go or so I thought. When attempting to kick start the bike, the action of the kick start has become notchy and clunky. I've disassembled and reassembled the primary drive a number of times but nothing seems out of place or odd and the problem remains.
Has anyone any ideas as to the cause/remedy? Any suggestions would be greatly appreciated.
 
If you think it's the belt jumping or the clutch playing up take the primary side off and try to kick start you should be able to see what is going on.
Dave
 
Kevin McDermott said:
I'm currently attempting to successfully install a RGM belt drive to my Mk3. The kits installed and I'm happy with the tension of the belt, the primary is reassembled And I'm ready to go or so I thought. When attempting to kick start the bike, the action of the kick start has become notchy and clunky. I've disassembled and reassembled the primary drive a number of times but nothing seems out of place or odd and the problem remains.
Has anyone any ideas as to the cause/remedy? Any suggestions would be greatly appreciated.
Click to expand...

It sounds like the belt might be slightly loose. If the belt climbs to the top of the tooth when you kick it -it will stop the kickstarter mid kick or jump the tooth.
Just tight enough to keep this from happening is the correct adjustment. Just a little too tight and the belt will fail the first time it gets hot.
Make sure you adjust the belt by starting out too tight and then move the adjusters to push the trans forward until the correct tension is achieved.
If you use the tensioners to tighten the belt, then when you apply power the trans will move back by the small amount of play in the adjusters, due to the pull of the rear chain. This will overtighten the belt and failure will follow soon.
 
MK3 transmission is fixed,it doesnt have the top slotted holes in the cradle and adjusters. Not sure how the tension
for MK3 belt drives is achieved
 
I believe it is the same as with my 1360 Vincent- the belt is supposed to be the correct length as supplied.
That particular motor has a Newby setup, but same idea.
The belt has enough slack when cold to give it a full 90 degree twist at the midpoint between pulleys just with finger strength.
There is no belt slippage with that one when kickstarting, and it is effectively about like kickstarting two Commandos at the same time.
Glen
 
madass140 said:
MK3 transmission is fixed,it doesnt have the top slotted holes in the cradle and adjusters. Not sure how the tension
for MK3 belt drives is achieved
Click to expand...

The RGM belt drive kit for the MK3 has an upper bolt that has been undercut where it goes through the cradle holes.
Questionable engineering but it is simple and seems to do the job.

I used tophat style bushings to mount the trans at the correct position on my bike. No adjustment.
 
madass140 said:
ahh, ok. I relocated the top hole in a MK3 cradle.
Click to expand...

Well, I relocated the bottom hole on my MK3 cradle by drilling it larger and then using an offset bushing. I didn't like the idea of the undercut bolt....

Here is the bolt that came with my MK3 kit many years ago. Still in my toolbox...

RGM Belt drive issues (2018)
 
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Are these MK3 belt drives using the Estart or doing away with that?
I can't imagine the Sprag would last without lube.
Or does the belt run in oil?

Glen
 
worntorn said:
Are these MK3 belt drives using the Estart or doing away with that?
I can't imagine the Sprag would last without lube.
Or does the belt run in oil?

Glen
Click to expand...

The belt will run in oil. That is the only way of keeping the e-start with the belt drive [unless you like sliding to a stop after the large gear seizes to the crank]

Unfortunately that does away with most of the advantages of the belt drive.
 
Jim
Do you use transmission fluid or motor oil with your set up?
Also as I recall you said you had to do some machining on the clutch drum to get it to work with the RGM kit. What was the machining that was necessary?
Thanks, Ray
 
Scooter62 said:
Jim
Do you use transmission fluid or motor oil with your set up?
Also as I recall you said you had to do some machining on the clutch drum to get it to work with the RGM kit. What was the machining that was necessary?
Thanks, Ray
Click to expand...

Ray,
I run my belt dry. The starter was removed many years ago. I use ATF in the transmission.

I have found it's been necessary to widen the snap ring groove when you use the later -thicker diaphragm spring. If that is not done the diaphragm will not be able to flex to the concave position. If it can not go slightly concave then the clutch pull will be heavy and the holding power will be light.
 
Thanks Jim
I was hoping the RGM kit would allow me to keep the starter since I herniated a disc and kicking isn't a good idea anymore. I had to replace some gears in the transmision a few year ago because of brinelling and thought replacing the chain with a belt might alleviate that problem.

Would using a hydraulic clutch eliminate the heavy clutch without widening the snap ring groove?

Thanks, Ray
 
I doubt that the belt would help the transmission. The belt has less cushion than the chain.
[think of all those little grease filled bushings in a chain to cushion the impact]

The groove will need to be widened -even with the hydraulic clutch. Jim
 
For whom it may help, the story of my last ride yesterday afternoon. The bike suddenly stopped at very low speed (about 20mph) with the engine completely locked. It couldn't be a seizure (low speed, mild temperature, no alert before, no change after cooling) and I started suspecting something suddenly and severely broken inside.
I started my investigations today, looking first at the drive side and noticed chips of alloy in the primary case, then a "floating" front pulley inner flange. Which was the culprit!
3 of the four scews securing it to the pulley where almost gone, acting as cutters on the crankcase and pushing hard enough on it to make the engine stall at idle and locking it.
Never had a look at this part during 10 years and about 50 000 kilometers, my mistake!
After clean-up, 4 new blue-loctited screws, and a with a re-machined crankcase, she's back on the road!
 
Kevin McDermott said:
I'm currently attempting to successfully install a RGM belt drive to my Mk3. The kits installed and I'm happy with the tension of the belt, the primary is reassembled And I'm ready to go or so I thought. When attempting to kick start the bike, the action of the kick start has become notchy and clunky. I've disassembled and reassembled the primary drive a number of times but nothing seems out of place or odd and the problem remains.
Has anyone any ideas as to the cause/remedy? Any suggestions would be greatly appreciated.
Click to expand...
Go back to the chain primary, use an iwis duplex chain on the two innermost rows and refit the electric start (if you still have it) The electric start can be made reliable. In my opinion belt drive kits for Mk3s are sold just to inflate the dealers pockets, the same as fitting PW3 cams, ok if going racing but not for road use. The sprag in Mk3s needs lubrication, so any belt fitted has to be able to run in oil (if the electric boot is still required)
Belt drives are good for racing and for eliminating oil leaks from the tin chain case on earlier bikes. Seen quite a few commandos with the belt shredded and the rider stranded, waiting for the recovery lorry. Ask any owner, with a belt drive fitted primary, if they carry a spare belt with them? I bet more than 50% of them will say yes.
A chain, even when worn out will get you home.
 
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