My WM20 is a non-runner and i have no idea when it did last run. So testing it on the stand, I noticed that the clutch would not disengage so I've stripped it down. I think it has a Triumph 4 spring clutch fitted. After stripping the clutch and removing it from the mainshaft I noticed there were no roller bearings anywhere. There appears to be an aluminium ring fitted to the centre of the chainwheel that provides the interface between the chainwheel and the mainshaft adapter. I'm guessing this is where the roller bearings should be??? Hopefully Ive managed to post some photos below so that you can see what I'm talking about.
Can anyone explain this?? Can I simply remove the aluminium ring and restore the roller bearings?

email (option): shaneambrose@hotmail.com

It looks to me like someone has tried to fit the 4 spring clutch without fitting the correct hub.
Your hub looks like that fitted to the six spring with a track for the caged ball bearings. The track should be smooth like in the picture below.
As long as there is no damage to the track in the basket you may get away with fitting the correct clutch hub (try Kiddiminster M/Cs) and a set of rollers. The hub is a special one for this conversion and not the standard Triumph one, so be sure to tell the supplier what you are doing.

A Triumph 4 spring clutch is not a bad conversion for these but as Pete said, you need the correct adapter. (I fitted a complete new one to my M20/Indian special that I bought from "Monty's" near Ian, mine includes a rubber cush which is not needed on an M20).

Maybe the previous guy thought that a white metal bearing would suffice, but you would need a good oil supply for that. If you acquire the correct Triumph center and adapter, bare in mind that the rollers are not the standard 1/4 x 1/4! The Triumph rollers are in fact about .012" shorter on the length. But Monty or Kidderminster will know that. Ron

email (option): ronpier@talk21.com

It's also worth noting that none of the adapters are a Triumph part...Triumphs have their own adapters...
When BSA bought out Triumph Motorcycles they quickly deduced the Triumph clutch was a better proposition than the 6 spring BSA clutch then in use...To enable the Triumph clutch to be fitted to the pre unit BSA swinging arm gearbox they produced the (BSA) adapter and associated parts...
Fast forward a few decades and people thought of fitting the clutch to the earlier BSA gearbox as their clutches wore out...Unfortunately although the swinging arm and earlier gearboxes share the same angle on the main shaft taper, the diameter of the taper is smaller on the s.arm box...So, when the BSA adapter is fitted to the earlier box it doesn't go on so far, causing a misalignment between the engine and clutch sprockets...For years the only simple way to overcome this was to fit a wider spacer behind the engine sprocket carrier and to either fit a weaker engine shock absorber spring or another spacer on the spring nut (to maintain correct spring tension)...
After a few more years someone made the wise decision to produce the adapter with a taper to suit the earlier gearbox (L.F.Harris I think) and these are now available to make the job easier...That adapter is an 'after market' part and as a consequence does not have a BSA part number...
The adapter and Triumph clutch are the basic kit but the correct clutch centre nut and washer are also needed as the BSA gearbox has a different thread diameter to the Triumph one...The washer and nut are BSA A10,late B31/33, Gold Star parts...When purchasing a clutch for use on a BSA single the clutch springs for the Triumph 650 twin are too heavy...There are two spring types, short heavy ones and longer lighter ones... Choose the longer, lighter ones for the singles to get a nice light clutch that won't slip...An alteration to the clutch pushrod length will also be needed...
The main takeaway from this is that if you are buying an adapter for a single be sure to inform the supplier of the application to ensure you get the right adapter...Ian

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

Thanks for the responses - great info and very useful

email (option): shaneambrose@hotmail.com

I want also replace the OEM clutch for the 4 spring clutch from Triumph. Could you send the link for shop where can i buy the correct hub adapter?

Thanks. Pawel

email (option): classicnortons@gmail.com

I got mine for the best price from Monty. https://montysclassicmotorcyclesshop.co.uk/

Ron

email (option): ronpier@talk21.com

FWIW
My first road bike was horrid mess of various A7 & A10 which some how managed to work together till they didn't,,,, big time
A speedway racer ( who taught us all to ride ) hear the racket from my clutch then dragged me into his workshop & got me to rip the clutch off
Apart from filing the chainwheel slots ( thats right there was no band on it ) clean & flat, by eye then braizing some key steel on the driven side for the plates to run against , he alo turned up a bush, similar to the one you have in some sort of bronze.

The clutch was beautiful to use, light & clean.
However you about 30 seconds with it dissengaged before it go hot enough for the bearing to grab.
But his mantra was always the clutch is only there to assist in gearchanging so no reason to be riding it .

An odd modification, with no real reason to do it other than a lack of willingness to source and use the correct components, which are widely available...Slow moving traffic would be a situation where you may well ride the clutch for example...And I wouldn't recommend trying it on Gold Star with a RRT2 gearbox..:laughing:...

I consider this is both an unnecessary and ill conceived modification with a high probability it would be problematic in the real world...Ian

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

A job suitable for time when it was done
his was Australia where the road traffice was fairly light
The drum mod is one I have done several times in order to resurect sawtooth slots in chainwheels & when done properly works a treat.
And no never done a bronze bush replacement for the balls but the 6 sprig is fundamentially a poor design requiring the drum to move which of course then has it out of alignment with the primary sprocket .
OTOH
I quickly acquired te skill of doing clurchless gear changes and slipping the bike into neutral before coming to ma stop.Now days that is illegal in NSW
We are supposed to sit at traffic lights in first gear holding the clutch in with one hand & holding both brakes on which of coure leave only 1 foot to be on the ground balancing the bike which is "fun" if there is a strong gusty side wind blowing.

The purpose of posting was to let Shane know it is not the first time this has been done and it will not cause the planets to stop revolving if he was to continue to ride his bike as is while he is sourcing correct parts .

In the days when these bikes are very much toys it is easy to forget that not all that long ago they were daily transport
SO the idea of the bike sitting idle for a week or two while the owner sourced the correct parts was totally foreign as it HAS to be running tomorrow or I can not get to work.

I've seen refurbishment of the clutch drum slots using the method you describe...I've also seen them welded and cleaned up to achieve the same result...That certainly extends the life of the clutch drum, though getting a full set of symmetrical slots is unlikely and in that case an unequal load is then applied to the clutch plate tangs/slots ensuring a rapid return of the same problem...That said it's a workable solution...

My criticism was of the conversion to a plain bush instead of rollers...I didn't make that clear in my post. I don't think it's a good solution as it is prone to failure without constant consideration of clutch use...I did also note one circumstance where slipping the clutch is common, apart from the fact that is done momentarily every time you pull away or when selecting neutral...There might be lubrication issues as well if the bush clearance was held to anything like a bearing tolerance and oil levels in the (leaky) primary chain case were not studiously maintained..If more clearance was used then the operation of the clutch would be no better than that provided by worn bearings etc...
Sorry, it's just my opinion but I'd never accept that as a good modification...I'd be more inclined to looking at modifying the clutch etc. to fit a ball bearing instead of loose rollers. I did exactly that to enable a Triumph clutch to be fitted to my WB30 and in terms of free play of the clutch drum etc. it was an improvement over the original set up...Shouldn't any modification be at least as good as the original arrangement?...Otherwise things are just going backwards....Ian

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

wm20
I thought everyone came to a stop in neutral because it's the sensible thing to do. I haven't heard about having to stay in gear with the clutch in at lights, don't have to do it in SA but I suppose they'll get around to it. I always ride with a spare clutch cable, now I'll have to carry 2. The local authorities here's particular interest is to slap ever lower speed limits on any road they can find.

I've heard of that ridiculous practice being taught my motorcycle instructors in the UK...There is no logical reason to 'sit on the clutch' at a junction that I can deduce...I generally select neutral as I come to a halt and always have done...Ian

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

I saw the sitting in gear approach advocated on an American site. The idea is that you're ready to drop the clutch & get out of oncoming danger. I hae ma doots.

I don't recall having to do that in 52 years of motorcycling and about a trillion stops at junctions....However, I think you should stare upwards as well in case something drops out of the sky....:small_airplane: :comet: :laughing: ...Ian

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