Last season, I had a problem that gas would overflow the tank out the breather tube at the cap of my 96 ZX-6R. It would only happen when the tank was full, or close to full, and the bike was sitting.

When I took the tank off at the end of the season (only had the bike for the last 2 months of the season) to prep for paint, I found the rubber drain tube at the base of the tank had been tied in a knot and zip-tied 3 times, which I promptly removed.

Any idea if/how the tied overflow tube would have caused gas to back up through the breather tube and forced it to overflow onto the side of the tank?

 

??????? I don't know, but can I guess?? lol

The fuel gets sloshed around and ends up in the overflow lip in the top of the tank. Normally this would drain down through the hose, but since your hose was blocked, it had no place to go and overflowed...??

 

Only guess i would have other than the one posted, is that you had air coming INTO the tank and coming out of the top, or you were riding upside down, that would make gas come out hehe.

 

Inverted riding They say that a formula 1 car could drive upsidedown if there was a track that could invert it.

 

Last time I tried inverted riding, I got skinned up pretty bad!!!! lol

 

+1 on the responses thus far. I will also add that if you filled the tank right to the top and then let it sit for a while the cold gas from the underground storage vessel could have expanded when it warmed up in your bike. The expanding volume of gas had nowhere to go due to the tied overflow and and forced its way over the tank.