It would be rare for one of these engines to remain with a dry sump after standing....those that do have had the best of everything. So most end up with oil in the sump after standing for a while, which should clear after a few minutes running. A good strong return into the tank reduces to a series of gulps on tickover as the sump clears.
But White Smoke from the exhaust on a run, if this is the case, makes me think too much oil in the wrong place. More than usual......Valve Guide or head gasket problem? Or simply too much oil in the sump passing the rings and causing the white smoke. A small amount of oil in the combustion chamber give blue smoke, as in worn bores and rings. The indication that it wet sumps means an imbalance of feed and return.... The scavenge capacity is greater than the supply side, so sorting this out is a first step. Looking for scored bores and broken rings comes later.
The conundrum that is the BSA lubrication system and its foibles are well documented on the forum and must hold the record for the number of possible causes. Baffled, Confused and Covered in Oil was a thread that ran over several weeks and was eventually solved by something simple, so worth revisiting.
If you take off the timing cover, check the oil pump is still tightened down, dig further (pump off) and you can check the pickup pipe is clear and the ball valve on the end of the pipe is not stuck. Clogged sump gauze also a suspect. Pump gasket also noted to be problematic, some examples obscure the oil ways. The anti wet sump ball valve mentioned has no role in regulating oil flow into the timing bush, some folks remove the ball and spring and rely on the oil tap in the feed line trick, with no change to oil delivery.
Swarfy.
