WD Motorcycle forum

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Feb 24, 2024 - 1:58AM

Re: 1942 M20 possible clutch conversion

Ian, as I am using the late preunit bsa 4 spring clutch can you advise the " few things to note" when doing this conversion. Thank you Charlie

email (option): millcrocfarm@gmail.com

Darryl Gubbels

Feb 19, 2024 - 9:00PM

Re: 1942 M20 possible clutch conversion

Barrett

Hi everyone I am here in the states and have always had a hard time tracking down a vintage motorcycle mechanic especially one who will work on a bike this old. I have a 1942 BSA M20 and have done a ground up restoration. I have had it running and the gears change when the bike is not running but when I have tried to put it into gear the clutch will not engage. I have the single spring clutch and took it out and rebuilt with all new components and it still does not look like it is separating enough even with the lever all the way engaged. I recently read a post on here where there was a conversion to a triumph clutch. I really love this motorcycle and would love to see it on the road even just to drive it around the block. If it is a strong recommendation to do the swap would someone please tell me all the parts I would need for my motorcycle. I saw in one post that you need the adapter and that Monty sells them but it says BSA 4 spring clutch. It will be an expensive swap but if it gets me on the road I am willing to do it. Thank you for any help. If you know anyone in Arizona that works on these that would be great to.

I use this clutch on my WM20.

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

Works very well and I am very happy with it! The clutch is very easy to assemble, simply fits on the original parts.

Retracting the clutch is also very easy and can be operated with one finger.

email (option): darrylgubbels@gmail.com

Barrett

Feb 19, 2024 - 11:12PM

Re: 1942 M20 possible clutch conversion

The fiber discs were almost like they were glued to the steel plates. I don’t know how that would have happened. Needless to say I will be ordering all new fiber discs and steel plates. The fiber discs are .125. I ordered them from draganfly. I am going to order all new ones. I had a total of 7 fiber and 7 steel. So now I will be running 6 hopefully that works. Is there an overall dimension of what all the fiber discs plus steel plates should be? Thank you for all your help I’ll let you guys know when I get it back together and if it works.

Barrett

Feb 19, 2024 - 11:46PM

Re: 1942 M20 possible clutch conversion

All I need is that kit nothing else? So I’m guessing you do not need to utilize the single spring? I cannot read some of the stuff in that page. It’s not a bad deal if it works smoothly seeing I need to replace this anyways

Ron Pier

Feb 20, 2024 - 6:11AM

Re: 1942 M20 possible clutch conversion

Well those new friction plates are each 1/32" too thick. Also you should end up with one less steel plate than fibre plates. (not equal amounts) If you simply add up the original sizes 8 x .093" and 7 x .048 the total is a little over one inch.

It's a sometime occurrence that clutch plates will stick together if left for any length of time. Pulling in the clutch lever and using the kickstart will usually free them.....But not always!! Ron

email (option): ronpier@talk21.com

jeremy atkinson

Feb 22, 2024 - 11:07AM

Re: 1942 M20 possible clutch conversion

I was advised that my clapped out gearbox [sidecar use] would work ok if I changed the equally knackered 6 spring clutch on my 1954 M21. I got the clutch kit from Kidderminster Cycles and all I had to do was shorten the pushrod slightly. Clutch is brilliant and the gearbox now acceptable. One has to make sure one gets the correct adaptor as the one for BSA twins is different.

Mark Cook

Feb 22, 2024 - 11:13AM

Re: 1942 M20 possible clutch conversion

So far I'm very happy with my single spring clutch.

Mark

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

Ian Wright

Feb 24, 2024 - 8:22PM

Re: 1942 M20 possible clutch conversion

You will need the correct clutch adapter..The type for swinging arm models is incorrect...In recent years this adapter has had the taper diameter altered to suit the M20 mainshaft AND give the correct alignment with the engine sprocket..You will also need the BSA type mainshaft nut and washer (remember these are basically Triumph clutches)....There are two weights of springs for the 4 spring clutch...A shorter 'heavier' one and a longer less 'heavy' one...You need the longer type for the M20 for a nice light clutch action...You will also have to alter the length of the clutch pushrod slightly...Finally run a 15W-20W oil in the primary chain case to reduce the inclination of the clutch plates to stick together when left standing...Ian

email (option): ian@wright52.plus.com

Darryl Gubbels

Feb 24, 2024 - 9:49PM

Re: 1942 M20 possible clutch conversion

Barrett

You mean the clutch set from the Netherlands? Everything you need is in the kit. The clutch remains quite original. This set actually only replaces the central spring with smaller springs. And you get better clutch plates.

It is only important that you have the correct center nut. I had a shorter nut and therefore the clutch did not work properly. The seller helped me very well with this! There is also a manual with photos included.

He doesn't have a huge stock of clutches, so it's best to send an email.

I had to wait about 2 weeks until he had another batch ready.

email (option): darrylgubbels@gmail.com

Mark Cook

Feb 25, 2024 - 10:44AM

Re: 1942 M20 possible clutch conversion

Darryl, do you have any more information on this clutch conversion or pictures?
Contact details?

Mark

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