Can a bad gas cap cause fuel to dump from overflow lines???

[PAGS550]

i have a 1977 GS550...cleaned carbs,,,runs excellent...occassionally it will spew gas from overflow tubes while idling....i have checked and rechecked numerous things such as float height..float stcking...carb cleaning...today it started and i shut it off and loosened cap ...tightened back up and started and it no longer leaked gas...can the cap itself be the culprit?? i attempted to clean it as good as possible..

[tkent02]

The tank is vented through the gas cap, so if the vent is clogged and the tank gets pressurized by sitting in the sun it could push fuel past the needle valves. In this case it would spill out the overflows. It will also starve for fuel when the fuel level drops, causing a vacuum in the tank.

Leave the cap cracked and see what happens.

[Guest]

There's a little hole also (at least on my 1000) inside the gas cap filler neck that acts as a vent, be sure that isn't clogged. Unvented gas tanks for whatever reason build lots of pressure from heat as well from just being ridden.

[BigD_83]

There's a little hole also (at least on my 1000) inside the gas cap filler neck that acts as a vent, be sure that isn't clogged. Unvented gas tanks for whatever reason build lots of pressure from heat as well from just being ridden.

What is the most effective way of cleaning that vent?

[Guest]

What is the most effective way of cleaning that vent?

If you're referring to that little breather hole in the filler neck, I just poked a wire through mine after the tank was sealed and it was clogged with sealant (POR-15).

[BassCliff]

Hi,

For reference.




Thank you for your indulgence,

BassCliff