gas cap leak?

just cleaned both the pilots in my 930. bike starts a lot better! however, i don't know if it's coincidence or not but i'm now leaking fuel from the gas cap it seems. the rubber seal in the cap is old but seems serviceable. after i shut him down i waggled the bike back and forth and sideways, no leak. anybody have any experience w/ this? thanx, rick

Gas cap as in the one on top of the tank?

gas cap on the gas tank

The original cap has a vent in it - a little pin hole in the metal disc that holds the rubber gasket. If that vent is plugged, it could pressurize the tank and cause weeping around the cap.

Mine leaks, I notice it if the tank is full, it seeps over the right hand side of the tank.
I have not sorted this issue out yet.
When I had a blocked vent the bike would stall out after 5 or 6 miles, with a vacum in the tank preventing any fuel going to the carbs, rather than a positive pressure problem it was a negitive pressure problem.
Stu

I have seen several tanks, both steel and fiberglass leak where the filler neck (cap mount) is bonded or welded into the tank. Using a slosh sealer (Caswell for 'glass or steel or Red-Kote for steel) making sure to get film build around the neck took care of the issue. This drove me crazy on a steel interstate tank. I replaced gaskets, bought a new cap, filed the mating surface flat, all to no avail. Then I realized the gas was coming from between the tank and the neck!

thanx guys. fitted the cap off my '74 project and no leaks. the original seemed to be partially blocked and i cleaned it.