Put some safety glasses on, and an old shirt.
Take off the oil pump, and blow air into the oil passage (hole) in the crankcase (where the oil pump sits) that delivers oil to the timing bearing (note that the anti- wet sumping check valve is behind this port).
Air (and oil) is likely to blow out at you, from between the crankshaft journal and the bore of the timing bush. Often it will also blow out from between the outside diameter of the bush, and the crankcase housing, as the bore in the casing usually elongates with time (rpm, lots of miles on the road).
If any air comes out (at you) then so will the oil when the engine isn't running, because the anti-siphon valve is not 100% reliable - the spring is very light, and long, and the ball seats in the alloy crankcase (prone to damage on the counter bore where the ball seats).
This is an easy way for you to gauge if the clearances are too great; if you emerge looking like a 50's rocker with bryllcream in your hair, then there is too much clearance - speaking from experience!
In summary, heavy wet sumping can be caused by:
Excessive wear on the timing side crankcase journal
Ditto for the timing bush bore
the bore in the crankcase half (for the timing bush) out of round; often between 0.010"- 0.014". If this is the case the housing should be bored until the bore cleans up (is concentric) and an oversize bush made with 0.0015"= 0.002" interference fit.
Worn oil pump
Oil pump not sitting flat on the gasket
Richard
