B52/ amc

[djbuk]

Hello chaps, just wondering if anyone else has had this clutch problem, it's a 55 model 20 that i've had about 8 months, it had the usual chaincase oil leak or so i thought,but i wanted to put some miles on the clock. anyway i got around to fitting a new seal and clamp, still leaking, eventually foud that it was leaking from the back of the chaincase and onto the band, also the gearbox oil had to keep being topped up so with anew gearbox seal istripped it down again, it was only when i refittrd the inner chain case that i noticed that the lip that diverts the oilaround the clutch shaft hole had been hammered flat i then tried another inner chaincase but now the back of the clutch is rubbing on the oil channel lip.It's fitted with aB52 g/ box with an amc 3 spring clutch and a3/8 spacer behind the clutch hub, i don't want to fit a longer spacer as the shaft splines only fit about 2/3 the way down the clutch hub splines with about 6 threads protruding for the clutch hub nut without a washer,hence plenty head scratching, any ideas

[GOLDSTAR]

can I suggest that its because it was rubbing the oil lip was flattened by a previous 'owner', ?why has it got an AMC clutch on it? my ,57 comp motor does not have an engine shock absober so with a Burman box required an AMC clutch so I had a similar problem to yours, however although the rear of the clutch was close to the inner chaincase it did not foul it, is it the correct mainshaft there are a few, I also had to fit the spacer to the rear of the chainwheel but it did work in the end, your right about the threads remaining though, use locktite, makes you feel a tad safer, kind regards

[djbuk]

thank's goldstar,i assume it's fitted with the amc clutch is because it does'nt have the cush drive on the crankshaft, just a sprocket held with a bolt. the crank n/s shaft only sticks out of the crankcase 5/8 inch i also tried a burman cluch as on my 53 single but that wo'nt fit on the gearbox shaft either as the centre is to big so i'll have to have another think about this problem as i don't want to squash in the oil deflector ring. dave

[wilko]

You must have a later crank in it then. On b52 boxes they have a separate piece that slides onto the shaft to take the burman clutch. Have a look at the parts lists on Christians Archives.

[john]

From my experience (see posting “B52 to AMC”) the primary chain run on the B52 set up is 1.6mm near the centre line of the bike than with the AMC setup. When I fitted an AMC box to my 1952 bike I also fitted the later longer spacer behind the engine shock absorber (023066) to line the chain up.

Here comes the ifs and buts, But my setup was on a single, if the gear box set up on a single is the same as on a twin (I think it is) and if the old engine spacer 014295 can be swapped for the new 023163 you could win yourself a whopping 1.6mm extra clearance to put on your clutch spacer.

The trouble is knowing what you have fitted to your bike, the spares list states the size of the old engine spacer 014295 as 9/32” this might be a starting point.

John T

[zwarts]

From my experiences of Burman B52 boxes fitted with AMC clutches, when the primary chain line is correct (and it sounds as though you have the correct spacer fitted), the back of the AMC clutch will foul the rear of the chaincase, specifically the lipped 'seal' which is crimped in place. I am afraid that you will either have to fit a Burman clutch or remove the lipped washer. If it is any consolation you will find that the removal of the washer has little effect on the oil loss from this region.
Bob.

[djbuk]

i've had another look at this and found that if i fit a 60 thou shim behind the crank sprocket and make the clutch rear spacer 60 thou longer the chain line remains straight and the clutch hub misses the chaincase. because the rear spacer acts as a stop for the hub then the stops at the outer end of the hub splines are'nt engaging on the shaft and can be milled out to half their width to a depth of 5/16 inch then a top hat shaped nut would more than double the amount of thread engaging on the shaft as the round part of the top hat nut fits into the milled out section of the clutch hub, and thre would still be enough depth of spline left to fit a tab washer. dave

[wilko]

Why didn't i think of that? I've been fretting for the last year with mine knowing i only have a couple of threads hanging on! Brilliant! Mind you i never liked the sloppy spline fit , the splines aren't an exact fit!