primary transmission case is filling up with oil

[paologurrieri]

Good evening, the primary transmission case of my 1947 Ariel NG 350 is filling up with oil, probably from the engine. What could be the cause? I thought it was the crankshaft ball bearings, but at first glance they seem to be in good condition. Is it possible that there is a problem with the oil pump, which is not collecting enough engine oil, and therefore the engine case gradually fills up and the oil is pushed by the pressure into the primary case?
Any suggestions ?
Thank you all
Paolo

[Simon.Gardiner]

What's the oil return like, in the oil tank? On starting from cold (or maybe after being stopped for a while) I'd expect to see a continuous stream for a short time, then short spurts.
You could go for a run and then drop (or loosen) the sump plate and see how much oil comes out. Straight after a run it shouldn't be very much. If the oil pump return really isn't working properly I'd expect the exhaust to be smokey but if the rings are worn it might be smokey anyway!
Have you got the correct spacer behind the engine sprocket? There should be almost no gap between the spacer and the crankcase, where it goes through to butt against the main bearing inner.

SG