The BSA A7-A10 Forum

Technical => Clutch, Primary, Gearbox => Topic started by: Dave c on 12.03. 2019 16:53

Title: thread on plunger clutch drum
Post by: Dave c on 12.03. 2019 16:53
hi, can anyone tell me the correct size, nut and thread ,on the 12  clutch drum studs please?
Title: Re: thread on plunger clutch drum
Post by: muskrat on 12.03. 2019 18:52
G'day Dave.
2BA is the critter. 67-3266
Cheers
Title: Re: thread on plunger clutch drum
Post by: Dave c on 12.03. 2019 21:57
thanks musky, i knew someone would know! the threads have been knocked about a bit and did not want to force wrong nuts on , cheers
Title: Re: thread on plunger clutch drum
Post by: muskrat on 13.03. 2019 06:01
No worries Dave.
A good reference for nuts & bolts part numbers is http://stainlessbits.com/link12.html
Or if you can open an xls file download this from the BSAOCUK https://tinyurl.com/y3skzrxh
Cheers
Title: Re: thread on plunger clutch drum
Post by: Peter in Aus on 13.03. 2019 11:12
I leave the cover off and put just enough oil in the primary housing so as to splash oil up on the chain when hitting bumps. Been like that for a long time now with no problems.
Peter
Title: Re: thread on plunger clutch drum
Post by: Swarfcut on 13.03. 2019 12:06
By chance I had a couple of plunger primary covers in the parts washer yesterday, and noticed on one that the cut out for the oil level screw was further forward, the first screw on the bottom run, which I assume was an earlier part. This came with a Longstroke basket case.  This part has no provision for draining the case.  The other case has a cut out  nearer the clutch, allowing for a lower oil level, and this part also has a cut out for draining,  at the lowest screw. The casting numbers are the same, so anyone know which is which.

 Swarfy.
Title: Re: thread on plunger clutch drum
Post by: muskrat on 13.03. 2019 19:32
G'day Swarfy.
My A7 is a 51 model with the level in the first hole and had no drain hole (has now).
I leave the cover on. I believe it acts to strengthen the basket no chance of it spreading (most high performance clutches are banded for this). Also to keep "most" of the oil off the plates. My clutch slips if more than an oz gets in.
Cheers
Title: Re: thread on plunger clutch drum
Post by: Swarfcut on 13.03. 2019 19:47
Musky.. Thanks for that. It looks as if the early cover has the first front hole and the deep slippy clutch oil level. So this is actually correct for the Longstroke. I am also a believer in keeping the  clutch dome cover and just adding oil to a running engine until it gets picked up by the chain and flicks past the filler. That means it reaches the chain, but not deep enough to enter the clutch. Sod the level screw.

 Swarfy.
Title: Re: thread on plunger clutch drum
Post by: muskrat on 14.03. 2019 05:42
G'day Swarfy.
My A7 was the 53rd short stroke off the line. As usual BSA used up previous model parts if they could be made to fit, hence the rigid type tool box. When (not if) the oil tank ends up in the sump it overflows into the primary (almost a pint) and ends up with 1/2 cup in the clutch. If so I can't make it up my driveway!!!
Cheers
Title: Re: thread on plunger clutch drum
Post by: Rex on 14.03. 2019 09:34
Like Swarfy I've kept the cover on and just give the chain a squirt before each run. Even though I carefully flattened the primary cover and (as best I could) the crankcase plus a new oil seal behind the clutch, I just know that filling it as BSA recommended will only end in (oily) tears eventually.
Title: Re: thread on plunger clutch drum
Post by: Peter in Aus on 14.03. 2019 09:38

I leave the cover on. I believe it acts to strengthen the basket no chance of it spreading

 Yes that makes sense Musky, but I don't push mine as hard as you, so that probable why I don't have any trouble with mine! *shh*
Peter
Title: Re: thread on plunger clutch drum
Post by: Greybeard on 14.03. 2019 12:47
I've seen no reason to leave the clutch cover off. Sure, those itty bitty nuts are a nuisance but, not impossible. I've actually used my battery screwdriver, torque limiter set low, with a small socket to run them up after hand starting them.