The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => Gearbox, Clutch, Primary => Topic started by: Rex on 23.10. 2017 19:05

Title: 1951 A7 oil seal
Post by: Rex on 23.10. 2017 19:05

A quickie-
1) the oil seal behind the clutch in the primary chaincase, is it a generally available common or garden oil seal? I haven't drilled out the rivets yet to see.

Title: Re: 1951 A7 oil seal
Post by: morris on 23.10. 2017 19:45

SKF CR 20x37x7 are ok
Should be readily available in any bearing shop

Title: Re: 1951 A7 oil seal
Post by: Greybeard on 23.10. 2017 21:01

Quote from: Rex on 23.10. 2017 19:05

A quickie-
1) the oil seal behind the clutch in the primary chaincase, is it a generally available common or garden oil seal? I haven't drilled out the rivets yet to see.

Be careful working on those rivets; the metal is thin and the holes are close to the edge. I used tiny nuts and bolts instead of rivets but had to thin the heads so they didn't foul the gearbox sprocket.


Are you sure that seal is leaking? If you use ATF in the primary you can tell if it's coming from there. The primary case should have only enough oil to wet the chain. Other sources of oil in that area are gearbox output seal and engine breather pipe.

Title: Re: 1951 A7 oil seal
Post by: Rex on 23.10. 2017 21:20

I don't yet know if it'll leak or not GB as the engine is dismantled, but visually the seal is shot and needs replacing. I was afraid those rivets (or the size of them) was going to be problematic, so thanks for the warning.

Title: Re: 1951 A7 oil seal
Post by: Greybeard on 23.10. 2017 22:49

You might try blind Pop rivets but put them in from the back of the case so they don't protrude too far.

Title: Re: 1951 A7 oil seal
Post by: Greybeard on 23.10. 2017 22:53

Just had a thought: I may be mis-remembering the problem with the bolts or rivets. It may be the clutch case that was rubbing on the nut heads rather than the gearbox sprocket which really cannot be that close to the case. Sorry to confuse you but just be aware that there is not much room for anything larger than a small rivet.

Title: Re: 1951 A7 oil seal
Post by: morris on 24.10. 2017 11:48

To get rid of the rivets I made a ring of about 3,5 mm thick to go at the back of the primary. I drilled and tapped 3 corresponding holes 4BA size. I reused the front ring, made the screw holes taper and clamped it all together with three taper head 4BA screws

Title: Re: 1951 A7 oil seal
Post by: Rex on 24.10. 2017 15:30

That sounds like the way to go. Thanks.

Title: Re: 1951 A7 oil seal
Post by: a10 gf on 24.10. 2017 17:06

Used screws and nuts, secured with some loctite, working perfect.