I used to have one of those Dural alloy baskets on mine, it wasn’t branded as Dunstall back then but I got it from BBB, it was actually very good and lasted well. However I used an original clutch centre and found the opposite problems. There was quite a lot of wobble with no plates in. The clutch Cush drive was pretty well worn in every way possible. From the spider to the back plate. However the more I flatted and removed the wear from the back plate of the clutch drive the more tighter that clearance got and wobble got much less. I can’t remember how much less, by the time I got the clutch working something like decent I had already bought the Bob Newby
and still glad I did. It ended up on a friends bike and has been fine since.
I’d be interested to take one of those new centres apart and compare it against the A and B series clutch centres. The B series are narrower and i wonder if who ever is making them, is making them to the correct specification.
When I compared the overall 'thickness' of the complete clutch centre that I bought from SRM
it was approximately 1mm larger than the original that came off the bike. I'm not sure what the clearance should be between the back of the clutch centre and the chain wheel drum but I would imagine it's not that critical as the friction plate goes in first and therefore the plain plate would have plenty to bear on, as long as the gap is a bit less than the thickness of the friction plate.
I had to take 40 thou off the back of the clutch centre, which is about 1mm, so that seems to tie in with the difference I noted. I definitely think that the clutch centre was the cause of the problem. I still don't know the exact clearance is from the back of the clutch centre to the chainwheel, as it's not an easy place to take an accurate measurement. I know that I could get an 8 thou feeler blade all around it but because of the lack of space in there and the fact that the inside of the clutch drum in that area is not entirely flat, that was about the best I could do. The important thing is that there is enough clearance.
Once I had it clear of the chainwheel, I bolted the loose clutch sleeve, thrust washer, rollers, chainwheel and clutch centre together with a long bolt and some thick washers. I then managed to accurately measure the gap between the chainwheel bearing outer race and the inner shoulder at the back of the clutch centre with some slip gauges. I compared this with the other measurements of the sleeve, thrust washer & chainwheel and this confirmed that the gap was a little tight. I only had to take a couple of thou off the thrust washer to resolve this and now it's all assembled it feels absolutely spot on. It spins freely and there is hardly any 'wobble' at all on the chainwheel.
Have to say I like the alloy chain wheel, it just looks & feels nice and saving all that weight spinning around in there can't be a bad thing?
Cheers, Kev E
See you soon.