RGM Belt MK 3 belt drive tension.

hillbone · Feb 19, 2012

Gidday. I have fitted a RGM belt drive to my MK3 and done away with all the electric start gear. I am worried that the belt is too tight as the cam bolt provided reallt seems ineefective and after a few klms the belt seems quite tight. ( Half a twist ). Is this going to be a concern as the belt is not showing any wear after a 100klms but I have not yet racked up any decent distance. Has anyone manufactured a better way of tensioning the gearbox?

Cheers Hillbone.

comnoz · Feb 20, 2012

The relieved bolt supplied by RGM for the MK3 is completely worthless. It does not keep the rear chain pull from pulling the gearbox back and over-tightening the primary belt.

You will need to come up with a way to keep the gearbox in place. It can be done by converting to the earlier style transmission adjuster. One adjuster installed on the left side works nicely. Take a pre-mk3 adjuster and install a helicoil in the unthreaded hole. Then use it in place of the nut on the left hand side and use a long bolt installed from the right side. You will need to slot the upper holes a bit to allow some movement and drill a 5/16 hole in the cradle for the stationary part of the adjuster.

Another alternative is to bush the trans mounting holes to locate the trans permanently in one place.

cash · Feb 20, 2012

I fitted one of the early Mk3 belt drives and fitted a snail cam to lock the top bolt. It can be fitted in situ by drilling and tapping a 1/4" hole in one of the plates. The snail cam needn't be anything special just an offset hole in a metal disc would do.
Cash

comnoz · Feb 20, 2012

cash said:
I fitted one of the early Mk3 belt drives and fitted a snail cam to lock the top bolt. It can be fitted in situ by drilling and tapping a 1/4" hole in one of the plates. The snail cam needn't be anything special just an offset hole in a metal disc would do.
Cash

Great idea. Jim

slimslowslider · Feb 21, 2012

Truly a great piece of skilled work, to be admired by all..
Note: this is in new condition.

comnoz · Feb 21, 2012

Makes ya want to run right out and buy another one. HUH. :roll:

Scooter62 · Feb 21, 2012

I thought the output shaft on the transmission was fairly securely located by the hole it goes through on the inner primary. Does the oil seal on the inner primary case allow enough movement to make any meaningful adjustment to the belt tension?
My guess was that if the belt was too tight you needed a longer belt and the funny bolt that RGM supplied was only to adjust alignment of the output shaft so it would be parallel to drive side of the crank. BTW the bolt I got was marginally better made than the one Slimslowslider got. I'm sure not a lot of testing was done with this setup prior to marketing.

Scooter

biffom · Feb 21, 2012

cash said:
I fitted one of the early Mk3 belt drives and fitted a snail cam to lock the top bolt. It can be fitted in situ by drilling and tapping a 1/4" hole in one of the plates. The snail cam needn't be anything special just an offset hole in a metal disc would do.
Cash

Cash,

I'm intrigued - you don't happen to have a picture of that do you?

Many thanks,

Carl.

comnoz · Feb 21, 2012

Scooter62 said:
I thought the output shaft on the transmission was fairly securely located by the hole it goes through on the inner primary. Does the oil seal on the inner primary case allow enough movement to make any meaningful adjustment to the belt tension?
My guess was that if the belt was too tight you needed a longer belt and the funny bolt that RGM supplied was only to adjust alignment of the output shaft so it would be parallel to drive side of the crank. BTW the bolt I got was marginally better made than the one Slimslowslider got. I'm sure not a lot of testing was done with this setup prior to marketing.

Scooter

The hole in the back of the chaincase locates nothing. I normally remove the seal when installing a belt drive. If you don't remove it, the lack of lubrication will remove it for you anyway. Sometimes the hole in the chaincase needs to be enlarged a little to get the correct belt tension but the trans needs to be held in place by something more that a sloppy fitting bolt or the rear drive chain will pull the trans rearward in use and destroy the belt. Jim

Scooter62 · Feb 21, 2012

Thanks Jim, looks like the installation won't be a drop in

I was hoping to keep the electric start and use type F auto trans fluid in the primary. Do you have any ideas on how to keep the fluid in the primary without installing the seal? RGM recommended just greasing the sprag and gears periodically and running the belt dry. I'm a little skeptical of this considering the cost of replacing the parts if it doesn't work.

Ray

cash · Feb 22, 2012

biffom said:
cash said:

I fitted one of the early Mk3 belt drives and fitted a snail cam to lock the top bolt. It can be fitted in situ by drilling and tapping a 1/4" hole in one of the plates. The snail cam needn't be anything special just an offset hole in a metal disc would do.
Cash

Click to expand...

Cash,

I'm intrigued - you don't happen to have a picture of that do you?

Many thanks,

Carl.

I can't find the bloody camera as soon as I do I'll take one or you.
Cash

hillbone · Feb 22, 2012

Thanks everyone. I will have a look at a Mk2 setup and wait for some more photos to be posted.
Hillbone

cash · Feb 23, 2012

I hope this helps it's a bit out of focus but good enough. It's been there that long I'd almost forgotten it.

Cash

nortonspeed · Feb 23, 2012

hillbone said:
Gidday. I have fitted a RGM belt drive to my MK3 and done away with all the electric start gear. I am worried that the belt is too tight as the cam bolt provided reallt seems ineefective and after a few klms the belt seems quite tight. ( Half a twist ). Is this going to be a concern as the belt is not showing any wear after a 100klms but I have not yet racked up any decent distance. Has anyone manufactured a better way of tensioning the gearbox?

Cheers Hillbone.

Half a twist is just fine (equals about 3/4 to 1 inch total up and down movement cold)

RGM Belt MK 3 belt drive tension.

hillbone

comnoz

cash

comnoz

slimslowslider

comnoz

Scooter62

biffom

comnoz

Scooter62

cash

hillbone

cash

nortonspeed

Guest

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