I've run into another problem with my friend's 95 GS500E - or rather, he has and he brought the problem to me.

His bike is doing something a bit odd. When he comes in from a long run with a reasonably full tank, he will find gasoline bubbling up out of his gas cap through and around the lock cylinder. I assume this is from expansion due to the engine heating the underside of the tank. I see Suzuki doesn't seem to have parts like seals to replace or even a diagram for the cap available, only offering a complete cap as a solution.

I presume some seals in the cap have gone to hell, and/or there's some sort of vent or drain that's plugged. How would we fix this?

under the fuel tank there are 3 hoses 2 side by side that go to the petcock and the 3rds a breather tube for the tank maybe the plug or pipe is blocked or up the chicken??? I suppose if there was no where for the tank to breath the pressure push more fuel down the fuel lines?? I'm just throwing ideas out there lol

There's a vent in the gas cap itself. I've taken mine apart years ago. You have to remove the cap from the tank to get to it . Just be extremely careful. There is/are small springs that like to launch them selves into oblivion if I recall.

Quote from: X-ray on October 28, 2013, 07:13:55 AM
There's a vent in the gas cap itself. I've taken mine apart years ago. You have to remove the cap from the tank to get to it . Just be extremely careful. There is/are small springs that like to launch them selves into oblivion if I recall.

yup. ask me how i know this too lol

Okay, where does the vent exhaust to? Is there an overflow system?

It's been a real long time since I took mine apart but the vent is rudimentary at best. It might just be a ball bearing and spring type valve all contained in the cap itself. There is no over flow system per se except that third hose that drains through the tank to the atmosphere. The top of that line is under the gas cap and drains rain and/or spilled gas.

The gas cap vent lets air in so gas can flow out.

There is a drain for the area around the gas cap for water and spilled gas. That ends up down at the lower right of the motor with the air box drain hose.

Quote from: adidasguy on October 28, 2013, 02:38:43 PM
The gas cap vent lets air in so gas can flow out.

There is a drain for the area around the gas cap for water and spilled gas. That ends up down at the lower right of the motor with the air box drain hose.

Agreed, it vents negative pressure to let air in, though it has to bleed vapor pressure from the tank once it reaches a certain value, no?  Like after shut down or due to changes in temp.  Gasoline vapor pressure is pretty low, and walking by my GS when it's in the sun or giving the bike a wiggle after it's been sitting usually brings the smell of gas.  Hence, I believe California models have an EVAP system.

To OP, my only guess (a shot in the dark, really); perhaps the tank vent is clogged or stuck, causing pressure to have to push past fill neck gasket.  With this may come fuel due to sloshing, where as the tank vent may have better baffling to keep liquid out.



Dan