Wet sumping is caused by oil running out of the tank via the 'flow' side of the crankcase, through the pump, past the anti wet sump valve in the crankcase, then into the sump via the timing side bush. The anti wet sump valve in the crankcase is a simple spring loaded ball which is often ineffective. If the pump is in very good condition it will not allow much oil through so wet sumping may not be a problem. If the pump is quite tired and perhaps worn due to score marks in its body or slackness between the gears and end plates it will allow oil through, and if the anti wet sump valve isn't working very well either because there is debris on the ball seat the engine will wet sump. In the worst case the crankcase will accommodate the whole of the contents of the oil tank if the bike isn't run regularly. Nearly all A10's wet sump a bit and, after a period of ownership, you will learn how quickly your oil is escaping from the tank into the sump. The best cure is start the bike once a week and watch the oil returning into the tank. As soon as the return flow changes from a constant stream to an intermittent stream the crankcases are emptied of surplus oil. It is not a good idea to allow the bike to wet sump too much as this will create excessive bottom end pressure when the bike is started resulting in oil pouring out of the crankcase breather all over the garage floor, bursting gaskets and overflowing into the primary drive through the gaps in the cush drive. Don't be tempted to fit aftermarket anti wet sump valves as these can cause other problems in my opinion.
