Well I've run both my 600cc M20 and my BSA/Indian special with the single spring clutches for many years, both with one friction and one steel plate removed. Light as a feather with no slip or drag.

However the Indian engine has no cush in the primary circuit and it could be a bit harsh at low speeds, so after about 10 years, I replaced it with a Bonneville clutch with rubber cushions built in. It's absolutely perfect now.

But for an M20 you won't need a cushioned clutch, so a basic Bonny clutch would be fine, but you do have to have the correct adapter.

I bought my complete kit from "Monty's" Triumph Motorcycles in Devon. Ron

email (option): ronpier@talk21.com

Aloha,

Make sure the clutch rollers are 1/4" x 1/4". I was sold longer ones and the clutch did not work, tried every possible remedy before it dawned on me while I was calmly looking out a train window what the real problem was.

Best regards,

Simon

I had the same problem as you. First the rollers in the clutch basket were the wrong size, original spring was not straight. Bought a NOS one and had the same problem...

Then I bought this:

https://www.thb-support.nl/product/bsa-m20-koppeling-centrale-veer-vervangings-set-15-4311-15/

Works perfect! I can pull the clutchlever with one finger.

Or get a complete kit with modern kevlar plates:

https://www.thb-support.nl/product/bsa-m20-complete-kevlar-koppelingsset/

You'll need a complete clutch for a pre unit Triumph twin..(Bonnie, T110 etc.) with a non shock absorber centre...Also the correct clutch sleeve adapter for M20 applications..There are two possible clutch spring types, short heavy ones and longer, lighter ones..The latter are best for use on single cylinder bikes. You'll also need the BSA clutch centre nut and washer, not the Triumph one...
Monty is a longtime friend and lives near me. Consquently he's familiar with what's needed but make sure you tell him it's for use on an M20...He supplies L.F. Harris parts which I'd recommend as the best...Ian

One more question.
Is it a good idea to leave out 2 plates (a steel and a friction) on your single spring M20 clutch ?
I want to give it a try, maybe it helps in my endless struggle with false neutrals.

It's not a modern bike, feel the pedal as you move it. Get pressure on the lever until you feel it engage.

Mark

email (option): pes.sales@btconnect.com

Yes, leaving out two plates is a good idea as it allows more room for the plates to seperate but has no adverse effect on the operation of the unit...Note that original fibre plates are .093" thick when new...Many pattern plates are too thick by quite a margin..In that case removing two plates will restore the plate 'pile' to the original height but won't provide any more clearance than the standard set up....Ian