Hi, I can't get my head around the two valves. I am converting an 890 for road racing and have dropped the compression down and i am running Av gas, retaining the pilgrim pump and using a scavenge pump to return the oil to a tank, and no breathers are being used on the motor except for two on the oil tank. Can somebody explain how the oil comes out of the crankcase. I do know that it is backwards from my thinking, if the piston comes down it would should off the disc valve and not push the oil out so when the piston goes up does it create a negative pressure and lift the discs away from the brass rings and allow the oil to just dribble out, pulling my hair out hear and I don't have much to pull out. Thanks ray.