Hi all.
I’ve pulled my clutch apart for the first time and discovered an anomalie. I have 3 different width friction plates. I’m guessing replacement parts from different manufacturers.
Do’s fitting all friction plates OD125mm ID90.5mm give better results? Or is the single spring design so crude I won’t feel much difference either way.
Theoretically the greater the surface area the better, so the wider plates would be desirable...In practical terms it doesn't make any difference though... It's not really a crude design, in fact with the high number of plates it's more like a 'modern' clutch than most...
What is more important is the thickness of the fibre plates...Original plates were .093" thick when new...Some pattern friction plates are too thick and the overall increase in the hieght of the plate 'stack' is sufficient to compromise the operation of the clutch by reducing the amount of space in the clutch basket for the plates to seperate....
With the correct thickness plates used it's an old 'dodge' to leave out one metal and one fibre plate to improve the space for seperation...That has no discernable effect on the clutches grip either...
Check the clutch spring has parallel ends....Stand it on a flat surface and place a parallel bar or similar on top of it...It's quite easy to determine visually whether the bar is 'tilted'...If the ends of the spring are not true to each other the pressure plate will lift unevenly compromising clean seperation of the plates...
Finally, make sure the clutch operating arm on the gearbox is set correctly...When the clutch lever is pulled in fully at the handlebar the operating arm on the gearbox should be vertical to get maximum 'lift'....Adjust the screw in the operating arm until that condition is acheived, making adjustments to the cable as required during setting...Ian
Thank you so much Ian. Very valuable info.
Where do you buy your friction plates? Do you insist on a brand like Surflex. I’ve seen plenty available but they look like they are of Indian origin. Love India but they do it a bit differently over there.
I used to get them made by Safetek in a material that would run 'wet', so the clutch cover wasn't needed...
However, after many years use my single spring clutch was completely worn out so I changed to the 4 spring Triumph unit for which all parts are readily available....Details of that conversion would take up another post, although it's quite simple, but it's an option you might consider if your current clutch is badly worn....It's not cheap mind....Ian
If it eases your mind that same clutch was used on motorcycles with near twice the Hp of an M20 so it is more than good enough
It was used on the pre-war B series as well and there it was 1 set of plates shorter because the B's were "medium weight sports" bikes where as the M clutch was supposed to be able to haul a 1/2 ton of sidecar + load .
Post WW II nothing odd to see one with 2 x 44 gallon drums of oil or a 1/2 ton of coal in a commercial box sidecar .
