I have a '91 Springer. Sometimes while my bike is warming up oil will go up through the breather tube to the air cleaner. Sometimes it will dump a quart of oil like this. On one occassion I pulled out the dip stick while this oil dumping was going on and there was some pressure built up in the tank. Taking out the dip stick stops or slows down the oil flow out the breather tube. I have completely disassembled the pump and oil lines, cleaned and checked everything, put it all back together and was OK for a few rides. But the other day it did it again. Has anyone got any ideas what could be causing this?