Save yourself some future grief and dry lubricate the tip-over valve. Get some dry graphite aerosol spray from your local automotive supplier. Remove the tip-over valve, spray the dry lube into both ends and shake the valve up and down.
Correctly re-install the valve. You can easily check the fuel tank venting system...remove the gas cap, put a length of approriate diameter hose on the metal vent tube that you see sticking up from the restrictor plate inside the tank. Now, suck on the tube like you would with a drinking straw. If you can easily draw air, then the system is fine. You don't have to suck too hard...if you do, you'll draw up the ball in the valve which will close it. Just blow, and the ball will reset itself.
