When I start my M33 moving I have two problems. One is that as I start to move off, the bike is hardly driving until the last bit of clutch lever movement, when it comes in all at once. The other problem seems linked; until the bike is travelling at more than about three miles an hour it moves forward in jumps, then once it's going it seems fine. It started doing both these thing recently with no previous symptoms, and seems to get worse the further I go on any given ride. Of course it isn't conducive to safe moving out at junctions, or doing 'U' turns on country roads.
Any ideas?
Maybe the clutch centre nut is backing off.
It is indeed backing off, well done idie. I've just stripped the clutch, to find the nut didn't have a tab washer; no wonder it had backed off. Instead, it had one of those two part Nordlock washers which of course has failed.
Whoever put the nut on didn't use the proper tab washer because the splines on the clutch sleeve collar don't protrude through the clutch centre. I've also found that the clutch sprocket is not in line with the crank sprocket, at least in reference to the gasket face of the chaincase; the clutch sprocket is further out. The only other issue I found is that the inner ball race needed some gentle persuasion to get it off the clutch sleeve collar.
All I can think of is that there's some component that looks right but isn't the correct one, or something's been assembled wrongly.
The inner ball race is usually tight and as you put it needs gentle persuasion. The sprockets can be out of line for a number of reasons. The clutch adapters vary in how far they sit on the shaft taper. The sleeve that the front sprocket fits on have different thickness flange at the engine end.. Use a straight edge like a steel ruler against the side of the sprockets, if the rule touches both then it's alright don't rely on lining up with with the chain case. There are shims available to place behind the sprocket sleeve I have some on my bikes to line everything up.
The 6 spring clutch on the M33 Gold Star and competition models B32 and B34 used clutch sleeve 65 3873. The B31/B33 used the same sleeve up to 1955. For 1956/57 the B31/B33 used a different sleeve 42 3107 which moved the clutch out about 1/8 inch ( the engine sprocket cush assembly also change to suit on the B31/B33)
The 2 different parts easy to mix up and ix mixed up the alignment of primary chain suffers.
Quote from: JulianS on 12 Jul, 2021, 18:24
The 6 spring clutch on the M33 Gold Star and competition models B32 and B34 used clutch sleeve 65 3873. The B31/B33 used the same sleeve up to 1955. For 1956/57 the B31/B33 used a different sleeve 42 3107 which moved the clutch out about 1/8 inch ( the engine sprocket cush assembly also change to suit on the B31/B33)
The 2 different parts easy to mix up and ix mixed up the alignment of primary chain suffers.
I think you've hit the nail on the head. It seems I have the 42 3107 sleeve and as well as it moving the clutch sprocket out of line by an 1/8th the splines are shorter, probably by the same amount. I checked the alignment with a straight edge (idie was quite right) and it confirmed my earlier rough check of eyeing up on the chaincase. I just have to find the right sleeve now...
The bike is all back together again and I've done about 50 miles on it; I hope to get another ride in today. This is what I found and what I did.
The primary drive sprockets were pretty much in line, as far as I could tell. But I couldn't be sure because the clutch was not sitting straight; the back plate had been chafing away because (I presume) the clutch nut was loosening off. I bought a new one from C & D Autos.
I was given an old and abused clutch sleeve, believed to be from an M33. It was too far gone to use but it didn't fit anyway. But I compared it with the one I had, and realised there was much more metal in the rear flange; I could have the flange machined back far enough to fit a lock washer, and there would still be at least the same amount of flange remaining as on the clutch sleeve I'd been given. In the end there was slightly more, once I'd had it machined.
I rebuilt the clutch, and dry assembled the engine sprocket and shock absorber. I got my straight edge and some feeler gauges. The clutch sprocket was 1.25mm/0.049" too far in; it seems the sprockets had been in line before the clutch sleeve had been machined. Back I went to the engineering shop, and they machined the spacer that sits behind the sprocket for me.
This gave me an issue with the lock washer for the shock absorber nut. It is prevented from moving by having tags that fit into splines. These tags are bent at right angles to locate in splines inside the shock absorber sleeve, but this was sitting a little further back now. I filed down the tags until the lock washer sat flush, then did the nut up with a dab of thread locking compound. I put the bike back together and rode it on Sunday. All now seems well. Thanks all for your advice.
As others have found, the correct clutch sleeve is no longer available. I must have tried a dozen places and nobody had one. C & D Autos sent me a clutch sleeve to try; one of a batch where the taper had been machined more deeply than normal; I can't remember which bike it was for, but it would have held the clutch at the same distance out as the existing one. Knowing what I know now, I wish I'd bought it. Oh well.
I told them in an email:"You may find it useful to know (and it may help somebody else) that while the splines on that clutch sleeve were longer than the one I have (and unlike my one would then retain the lock washer) that clutch sleeve didn't sit any further back on the mainshaft, so my primary drive sprockets would still be out of line." Of course I now know that my primary drive sprockets were not out of line, but this may be a solution for anyone who is looking for a clutch sleeve.
I think that's everything. I'll find the thread I started about the shock absorber and put links in to tie this all together.
Link to thread about the shock absorber nut and lockwasher:
https://www.bsaownersclub.co.uk/bsaoc_forum/index.php?topic=12597.0 (https://www.bsaownersclub.co.uk/bsaoc_forum/index.php?topic=12597.0)