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Re: Clutch Plates & Slippage Problem

['Sounds like the four locking screws are the problem here! When I get back from work today I will try assembling without the four locking screws']...

The 'adjustment' screws and locknuts are fitted to the clutch nut to allow adjustment of the spring/pressure plate to achieve an even lift...They aren't 'locking' screws...

This was a REME modification that can be found in an addendum to the REME M20 standards book and works well to solve the problem of uneven clutch lift. As long as the screws fitted aren't overly long they shouldn't cause any problems...

I've carried out this mod. a number of times and in fact I recommend it if a new original clutch spring is not available and there is a problem with the old one...I believe it was Simon from Sweden who recently employed the method himself to improve his clutch operation...

The mod in itself will not contribute to clutch slip or cause clearance problems if correctly executed and shouldn't be condemned purely because it was not done correctly or some other factor is coming into play.......Ian

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

Re: Clutch Plates & Slippage Problem

If you have pattern fibre plates that are too thick you need to leave two plates out...From your dimensions each of your plates is oversize by 1/64" (.0156")...There are 8 plates so the total amount of surplus plate thickness is approx. 8 x .0156" or .1248" (1/8")....

So, leaving out two plates (one fibre and one steel) will restore the plate stack to pretty much the correct height...

Therefore this will have no effect on either the spring pressure or the proximity of the pressure plate/nuts to the outer cover, nor should it have much effect on pushrod length...However, a new pushrod should be fitted if it is required to achieve the correct adjustment of the clutch operating arm at the other end of the gearbox....It is important that the arm is correctly set to achieve maximum lift and that there is free play in the cable when the clutch not being lifted..
Check the free play at the operating arm as wear in the handlebar lever pivot can give a false impression...Also ensure the ball bearing in the clutch operating arm is unworn, of the correct size, can move freely and is lubricated with a little grease...

The clutch pushrods are not prone to flexing as long as everything is set up correctly and a standard length of silver steel (13") can be used to make any BSA heavyweight single pushrod when cut to the appropriate length and heat treated......

Check that the clutch plates are lifting evenly when the clutch is pulled in...If they are not a new spring will be required or you must make the REME modification to the spring nut to achieve that condition. When placed on a flat surface and checked with a straight edge the ground ends of the clutch spring should be parallel...After extended use the springs tend to settle out of parallel and the consequence is uneven lifting of the plates...Check that the spring itself is within the wear limits laid down...A worn or weak spring can also lead to clutch slip...

Also check for wear in the clutch basket and centre...These become 'notched' by the metal plates over time and the plates can then get caught up in the resultant grooves...Sometimes this prevents the plates going fully together under spring pressure resulting in clutch slip. The basket generally suffer from more wear than the centre in my experience...

Any notching can be carefully removed by filing, removing the minimum to clean up the surface. Try to remove the same amount of material off each slot if this work is carried out to maintain contact on all the plate 'tangs'...Ian

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

Re: Clutch Plates & Slippage Problem

Ian,

Thank you for all of the information. I'll methodically go through the list this evening. I think that I'm getting closer to solving this problem.

Best regards,
James

Re: Clutch Plates & Slippage Problem

Hello Ian,

I went through the list of the things you said to check. On one item, the clutch spring, apparently I made an error with the clutch spring measurement. It's definitely out of specification. I measured it and the results are the maximum length of the spring is 2-1/4" long on one side, and slightly below that on the other side. So a new clutch spring is needed. Second item that I found after close examination of the clutch basket is the notching that you described. After I struck a file on it I could clearly see the notches. There's more notching one one side of the basket slots than the other. I carefully filed a little bit realizing that in order to make the notches completely disappear, I would have to remove too much material. So I kept it light and did a little deburring to smooth things out.

I also re-fit the clutch nut without the adjustment screws on it. I then pushed the clutch rod in from the offside of the bike further in than really necessary, then I refitted the actuator cap to see how far the rod would go back in. Then I was able to see how much distance that I had from the clutch nut to the ball bearing on the actuator cap. It appears to now have plenty of clearance, about 1/4" between the cap and nut. Oh also, I did leave out the two plates in the basket.

So now I order the spring and wait for it to come in from your side of the pond! I've just received a great education of the finer points of a M20 clutch system, thank for your help. I'll follow up later and let you know how this all turns out.

email (option): jamescusteau@yahoo.com

Re: Clutch Plates & Slippage Problem

Aloha,

Like Ian said I did this fix a while back because I had a clutch that would not free at all. I never got back to y’all about the turn of events however.

It did not workout and I later found that the inner cage would bottom on the outer cage. At the time a made a shim and got it to work properly. In a later thread I read about suppliers supplying incorrect sizes of rollers and I believe that was the cause of the problem. On the website this supplier specifies them as being 1/4 x 5/16.
With the clutch cage sitting to far out on the spindle things get nipped up.

I emailed the supplier just yesterday and have yet to receive his response, but in due time I of course intend to replace the rollers with the correct size.
Too bad I made the distance piece for the cush drive to align with the clutch sitting on these rollers. And too bad I spent like three whole days trying to figure out why things didnt work...

/Simon

email (option): SimonofSweden

Re: Clutch Plates & Slippage Problem

For reference the clutch rollers should be .250" x .250" (1/4)...

Apart from the 1/4" x 5/16" rollers which are incorrect make sure any supplier doesn't give you Triumph rollers which are 1/4" diameter but .006" shorter(.244")....Triumph and M20 clutch rollers are NOT 'equivalents' as suggested by some...Ian

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

Re: Clutch Plates & Slippage Problem

Thanx for re-posting that info Ian!
Always good to have it in text in front of you and not just in the slightly dazed memory of a middle aged man. :D

/simon

email (option): SimonofSweden

Re: Clutch Plates & Slippage Problem

Ok a little update on the clutch rollers here,
(to lazy to search out my original thread but since the topic was touched on here I might as well hijack this one. But what happened was that the inner basket bottomed out in the outer with that one being to far out on the spindle. I then wrongly interpreted the lack of clutch action as being due to the clutch lifting in a tilted fashion and spent a lot of time fixing this. Only after that was taken care of and the clutch still was dead locked did I think to look elsewhere and realized the real problem.)

I got in touch with the guy who sold me the incorrect rollers 1/4" x 5/16". It was a long time ago and I really didn't expect much more than an apology.

Well I didn't even get that. He told me that I was the one to blame and who were to check that I ordered the correct part, he would take no blame in being at fault.
Now this of course doesn't make any sense. If you click on a website and follow the path BSA > M20/21 > AA Single spring Clutch > Rollers; you would expect that they would be for that particular bike now wouldn't you?

Anyhow, he previously stated this on the website:
"26-0650 M20/21 USE 22 of these 1/4" x 5/16" rollers"

And he now states:
"26-0650 M20/21 USE 22 of these 1/4" x 5/16" rollers
Some machines use 1/4 x 1/4"rollers. Please check before you order."

So at least some progress has been made.

I choose not to out his name here, because I just think it's kinda tiresome with people using the internet for getting back at people for little things. He has been a very good supplier of part for a long time before and after this and I really have no reason to jinx his business. Just wish he had a little less of male pride in him and admit that he was wrong.

best regards,

Simon

Re: Clutch Plates & Slippage Problem

26-650 is the part number for the 1/4" x 1/4" roller....Personally I have never seen a wartime or post war single spring clutch that has anything other than rollers of that size...

That said, pre war BSAs aren't my speciality so I'm ready to be educated...Does anyone know of a model that actually has a single spring clutch with rollers of of 1/4" x 5/16"....??...If there is one which model is it and what is the part number for the rollers?..Ian

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

Re: Clutch Plates & Slippage Problem

Hello All,

After installing a new clutch spring and removing the spring adjustment screws, I took the bike out for a test drive and the slipping problem has been solved! I left out one metal and one fiber clutch plate and the result is almost no tire spinning when in neutral while on the rear stand. The new clutch spring that I received from Dragonfly was slightly different from stock spring, it is slightly smaller in diameter and that is a problem when using the clutch spring compressor tool. The new spring fits inside of the compressor tool, so I drilled three holes in the side of the tool and threaded them, I then inserted Allen set screws and that allowed me to set the amount of screw grabbing the spring keeping in mind that in order to remove the tool the screws must fit through the cut outs in the clutch spring nut. Hopefully this tool modification helps anybody using a new spring.


email (option): jamescusteau@yahoo.com

Re: Clutch Plates & Slippage Problem

Good to hear, but why on Earth would they have had springs made, different from standard? Ron

email (option): ronpier@talk21.com

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