Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Belt alignment on early M3Ws

I doubt you would notice anything, it just causes wear on the belt and sprockets as the belt is tensioned and un-tensioned a small amount every time there is a difference in speed between engine and wheel.

A cush drive is just a form of shock adsorber that is found, mostly, in the transmission when a belt of chain is the final link. Some cars have shock adsorbers in the transmission, often in the form of rubber cushioned universal joints of some form.

Well interestingly it sounds a little mechanical to my ear. However it disappeared when I changed to my new dural sprocket. It reapeared when the sprocket had worn again. Tightening the belt again would probably solve the problem but I don't like running to tight as I worry about bevel box bearings. The local dealer thinks it's the belt possibly slipping a tooth but on balance I just think it's the snap of the belt. Happens if you let any backlash into the drive system.
Typically: overrun, breaking into slow turn, change down without a blip and therefore backlash (slack is maybe a better term) introduced. Open up gently and a noticeable little clunk. Only small but not a great sound. Doesn't happen if you get it right and down change into first blipping all the way and gently power out, but hey it's not always possible in town etc.

I'm with Wiscos, Feb. 2013 car on MK2 compensator, always heel and toe on down shifts to stop any transmission snatch, and all quiet on the western front.

I look with hope to find a solution yamaha rear pulley vx1900, the original assembly is a torque absorber for its power of 90 hp and a torque of 15 kgm.


if I work the more I have much more time to look to try other solutions.

Great post - I believe too that morgan have missed the trick in (a) not providing Cush drive & (b) not providing a pully with 2 protective flanges
I'm still running on a totally un-modified car, trying to protect my clunky old compensator for a few more thousand miles. (until I can get it changed) - Lack of Cush drive is also adding to its demise. Centa drive, cooling and bump steering should have all been mods provided by Morgan free if charge for early cars, and owners will continue to do development of the M3W free of charge for Morgan but that's another post

That Yam wheel and cush drive are exactly what MMC should have fitted.

The rear pulley is a bit large, but getting a custom double sided one made of the correct size isn't impossible.

The lower belt guard would also seem to be a logical idea.

I'm firmly of the opinion (until I'm proven to be wrong!) that the lack of cush drive is at the heart of the bevel box problems.

Why? Because I suspect those people who have had no problems with the bevel box and/or rear pulley wear have a certain driving style that serves to protect the box from torque reversal loads derived from the rear wheel.

I will put off buying a M3W until this issue is resolved...by someone..

Lucky or not
That is the Matter
We are two superdry owners
One with big modification ( carburator,exhaust ,wheels....)
And the second ( mine) strictly original) with 13000 miles without any problem

So, if I understand the drawing correctly, the Cush drive is comprised primarily of parts #5 and #11 and is, in essence, a "compensator" fitted between the drive sprocket and the wheel - a second compensator.

Yesterday I ordered a 65 tooth pulley HD fully chromed becaufe my third pulley adaptable HD polish lasts as long as the original morgan for me (10.000km), I also bought a gear-box for beve 35 teeth for future with the pulley yamaha 70 teeth, I'll have to find a carbon belt adapted the number of teeth.

Over all the years that Harley has been making bikes, coming up on 113, they only started to use the "cush" drive in '08 on their touring only bikes. Their cruisers, Dynas etc, still have the same bolted solid sprocket to rear wheel as before.

Japanese and probably European bikes have been doing it since the '50s or '60s.

I had ridden my friends Softail Deuce the few months before I bought my '08 Road King and boy was there ever a difference between the two.

You wouldn't think that the Goldwing is setup with a cush drive, but they are. Within the driveshaft there is an inner and outer shaft/housing and the two are connected with a rubber sleeve inside the tube. This gives just enough cushion to take the torque pulses out of the system.

In a V-Twin, the torque/firing pulses are very noticeable and that's what give the trans all the problems. That's why Harley has a compensator on the motor to isolate the pulse vibrations from the trans.

In the stock M3W intermediate drive compensator assembly, they have a rubber donut of sorts that does the last coupling between the flywheel and the compensator; at least that's what's shown in the parts catalog.

I remember my old BSA Victor 441 single, when I was on gravel roads or loose dirt, every firing pulse of the motor created its own little divot in the dirt from the back tire chunking. This was more noticeable in a higher gear and lower speeds with the cracking of the throttle.

I've always thought that M3W could just stack about four of the rubber donuts together and use that as the isolator instead of the compensator. Actually the rubber donut looks very similar to what I've seen on eBay for the rear of the BMW sedan driveshafts. They bolt between the rear u-joint flange and the third member flange. This give it a bit smoother feel.

BMW isolator:


Toyota isolator in a more refined manor:


Either of these could be stacked to provide more or less "cush" and I believe would be more than enough on the M3W.