Motorcycle Repair: Oil draining from tank into engine sump while sitting for long periods, vent tube, oil tank

Question
I have a 1991 FXR, after sitting for a month or so it will pump oil out the vent tube that connects to the air cleaner.
It will pump about a cup of oil before it stops.
Is there a check valve in the oil system that is suppose to keep the oil from draining out of the oil tank into the engine sump?
If this is the case where is it located, and is it easy to replace?

Thank you for your help

Frank Zappettini


Answer
there is a oil check ball in the oil pump. It is under the cap closest to the enging on the top of the pump not the one with the tower...   the one that is not on the tower, remove cap and then spring and the check ball. replace with new check ball and then spring and then install old check ball on top of spring and the replace the cap. This will apply more pressure to the check ball for a better seal.  Johnny