I am assuming the check valve/reed valve is defective, putting enough pressure inside to find path of least resistance. The part referred to as the reed valve is 26909-79. The check valve is 26909-82. The latter part is not found easily, on the XL forum a poster stated a dealer claimed it was not a good part number. The '79 part is still found at H.D. Has anyone experienced this trouble in a '84.5-'85 ironhead? There are only so many of the these models compared tothe rest it is hard to find good user information. This valve is located in the round end of the cam cover.