I have just finished rebuilding my B33 and filled the oil tank up and after a week or so the oil has seeped into the crankcase. Any ideas what the problem is? I have not started the engine yet.
Wet sumping is common on many "Dry sumped" British bikes.Its a while since I did much with a pre unit BSA engine, and there will be a specific answer to why your bike does it. Long term if the bike is only going to be used occasionally, then have a look here; http://www.kingpincomponents.co.uk/oil-taps-and-fittings
I saw these chaps at Kempton Autojumble, nicely made kit. My brother has fitted one to his G3L Matchless,I will be doing the same.
Can't tell you what the problem is, only that I think that something may be wrong because my 1958 B33 hold the oil (40 monograde) in the tank for many weeks with very little escaping to the sump. Same with my 1959 Matchless G3 (same oil), unlike my 850 commando which can hold the (50 monograde) oil for several weeks or drop it all to the sump within 2 weeks, just seems to depend on its mood!
Beware of taps and valves.
Below from the B31/33 owners manual.
Check the ball valve "A" is seating, reseat it with a tap with a hammer.
Thanks very much for the info chaps. I had forgotten about the ball valve in the timing case, so will take, out clean and re-seat and hope that does the trick. Will let you know later.
Regards
Mike