Finding the source of an oil leak

[AWJDThumper]

The felt washer is there to stop crud getting to the seal but is a pretty crude way of achieving this. It sounds as though the clutch seal is the main culprit and needs to be examined more closely. It might be worth checking the seal has been inserted the correct way around.

[Blackthou]

Phil,

Could it be there's simply too much oil in the PC? I know you added 1/4 pint but did you use the level screw? I've seen scenarios like this before when it was either too much oil per se, or just enough over to work its way out on a run.

[Phil C]

Well, I drained it through the drain hole and then put in 1/4 pint. I confess I was surprised when I drained it to find there was 1/2 pint in there rather than just 1/4 pint.  Phil

[Blackthou]

Hi Phil,

Was there a happy ending to this? Did the 1/4 pint of oil resolve it? I ask as I took my C15 out on its maiden run today (well for me after 6 months of ownership and fettling). The engine was beautiful, the brakes weren't bad unless braking into a corner then it squirrelled a bit. Ran well and sounded awesome.

I did 25 miles and checked her over when I got back. There was sign of oil on the top of the cranckcase which I deduced to be a weep from a rocker banjo (I had annealed the new washers) that had blown about and an oil leak on the pc wall just as your pictures and description. I'd put the amount of oil in as per manual but can't remember the volume.
 

[Phil C]

Good morning Rick, This conversation was continued in another conversation thread that was ongoing at the time, entitled "Clutch oil seal and sleeve gear bush". You might want to read that.
I still have some slight leak(s). I'm considering taking the clutch off again.
Please let us know how you get on with this. We might have the same problem.           Phil

[Blackthou]

Hi Phil,

Thanks for the update. Sorry for the time lag but haven't had chance to log on lately. I remember the other post and revisit it. I'm also wondering if I put too much oil in the PC. I only put in as it said but from posts there seems to be a debate between 500cc and 750cc. If I've put 750cc in, it could be the problem.

[Phil C]

Isn't that an awful lot of oil for the primary chaincase? I put in 1/4 pint, which I believe is about 142cc?  Could be different for your bike of course. Mine's a 1965 B40F.   Phil

[Blackthou]

Possibly Phil, I was talking from "memory". After I posted I remembered there's a level screw so that will my first port of call. Also, after the initial loss on returning from the ride, there hasn't been any since - while parked. Is yours like that?

[Phil C]

I'm a bit confused about my oil leak(s). To answer your question, Rick, yes, I think anything leaking from my pc is only when the engine is running. The vertical dribble lines on the inside of the pc are only there when I've been for a ride.

I think I also have a very slight leak of gear oil (evident because I put dye in the gear oil), maybe from a seal, but I've not yet begun properly exploring that. It's only very slight so I guess I could live with it, but I might try to fix it.

Please let us know how you get on. Good luck!   Phil

[Pete A10]

If it is only when it is running then it must be something quite high up in the PC. When standing all the oil sits in the bottom of the case. When it is running, oil gets thrown around inside the case and can leak out from higher up.
In that case there are three possible sources.
The central oil seal on the clutch shaft.
The perimeter of the sealing plate which gives access to the socket.
I also seem to remember that the set screws holding this plate on were not in blind holes but threaded right through. It is possible that oil can leak out through the threaded holes when it get hot. Resolve it with a bit of threadlock.
Hope this helps.
Otherwise accept that it is BSA. At least you know that you have oil in your PC!!

[Pete A10]

Sorry the second item should read sprocket not socket