I've been looking at the box of bits that is my M21 project and considering which way to go with the clutch.

This bike will be a keeper, something that I hope to ride quite regularly, and I've heard it said that the 6 Spring clutch is not the best and is often replaced by a Triumph unit. I've had a look at the technical section and seen Ian's very helpful article on dealing with clutch drag or slip but before I do anything with the existing unit I'm wondering whether to try and find a used Truimph unit to work with.

Any suggestions? And if I do go down the Triumph route, can anyone tell me please which one will be a straight swap for the M21 unit?

Gary.

email (option): gj.owen@hotmail.co.uk

My M33 had the single spring clutch which I found rather heavy, I replaced it with a six spring clutch and have had no problems with it and the extra 8 bhp over the M21.

I'm not a fan of the 6 spring clutch personally and would opt for the Triumph unit every time in a 'pick one of these two' competition...

There are plenty of good used Triumph parts still to be found at the jumbles and some good quality new parts...I tend to use the parts manufactured by L.F. Harris for mine...

Any clutch for a pre unit 650 Triumph will do the job (Tiger 110, Bonneville etc.)...

You will need the gearbox main shaft adapter and the correct center nut, washer and tab washer used when this clutch is fitted to a BSA...If you buy parts for a late Super Rocket for example these are all the right parts as BSA fitted the Triumph clutch to late models from the 50s onwards.......

The standard BSA main shaft adapter was made for use with swinging arm boxes and will cause the clutch to be slightly misaligned with the engine sprocket when fitted to a rigid or plunger model....

All the gearboxes have the same taper on the main shaft but the diameter is different for rigid/plunger and swinging arm models...

This can be rectified in two ways..

First...Buy a clutch adapter from Kidderminster Motorcycles...The sell one that has the taper modified to fit plunger/rigid models correctly..

Second...Fit a standard clutch adapter and clutch. Then check the amount of misalignment and fit a spacer of that thickness behind the sleeve that carries the engine sprocket....

Some sleeves have a spacer fitted behind them already...In that case make a single spacer combining the dimensions to produce one spacer of the correct thickness...

Other sleeves have the 'spacer' incorporated as part of the sleeve...In that case you will see a shoulder on the rear of the sleeve and you only have to add a spacer equal in thickness to the measured misalignment...

The amount of misalignment is usually approx. 1/4"....

After fitting the Triumph clutch you will also have to alter the clutch pushrod length to suit...

It all sounds a bit complicated but it's a very easy conversion once you get into it....Ian

Hi,

I just wanted to say that, Ron Pier gave me some advice and I must say it made a big difference. I have my standard WM20 clutch, Rons advice was to remove one friction plate and one metal plate. Spot on, no more heavy clutch and easier gear changes. Plus when your doing a lot of stop starting they get hot and the slipping/snatching gear change is eliminated too.

Not sure if this helps you , but all the best.

email (option): T58white@hotmail.com

Quite right Ross. I run my WD M20 with 600cc engine and my much more powerful Indian special with WM20 box and single spring clutch. Both with the two plates removed and both are so light and no slip or drag. Ron

email (option): ronpier@talk21.com