Crazy Gas Cap Question

[gbw]

Just bought a new gas cap for my 77 GS750B from Bike Bandit. Filled 'er up to the top and parked 'er in the garage on the center stand.

A little while later I noticed the tank was wet. I had just washed 'er so I wiped it off thinking it was water but thought it smelled like gas. Didn't give it a second thought.

An hour or so later I noticed the tank was covered in gas and gas had run down the tank toward the seat, had run down both sides, and pooled on top of both side covers. None had reached the ground yet but another hour and it would have surely puddled there.

What is going on?

The reason I bought a new gas cap is that with my old cap I had to park using the center stand for the 1st 20 miles or so after a fill up. If I forgot and used the side stand gas would leak down the left side of the bike from the cap. As long as it was on the center stand everything was fine.

Why would my brand spankin' new gas cap push gas out all over the tank? The bike is on the center stand for cryin' out loud.

Any thoughts? Thanks!

[focus frenzy]

you put in to much gas!!!

the caps are vented so as the gas heats up (sitting on top of a 750cc heater) it expands and has to go someplace and that is out the vent and down the outside of the tank.

late model flush caps have a internal overflow drain that lets excessive gas go down a internal drain and to the ground via a drain hose instead of all over the tank.

[gbw]

you put in to much gas!!!

the caps are vented so as the gas heats up (sitting on top of a 750cc heater) it expands and has to go someplace and that is out the vent and down the outside of the tank.

late model flush caps have a internal overflow drain that lets excessive gas go down a internal drain and to the ground via a drain hose instead of all over the tank.

Thanks ff. This makes sense I guess. I did fill it up right to the top...and I mean the very top. But, this is just the same as I always did with my other cap and it never leaked like this. Only if I put it on the side stand.

How full should I fill it? Is there a visual indicator somewhere I can reference? I don't remember seeing anything in the owners manual or Clymers about how much gas to put in.

I figured put as much gas as possible so I don't have to stop as much

I always fill up on the center stand. Maybe I should fill up on the side stand to make sure I don't over fill.

Ride, ride, ride, let 'er ride

[Larry D]

Thanks ff. This makes sense I guess. I did fill it up right to the top...and I mean the very top. But, this is just the same as I always did with my other cap and it never leaked like this. Only if I put it on the side stand.

How full should I fill it? Is there a visual indicator somewhere I can reference? I don't remember seeing anything in the owners manual or Clymers about how much gas to put in.

I figured put as much gas as possible so I don't have to stop as much

I always fill up on the center stand. Maybe I should fill up on the side stand to make sure I don't over fill.

Ride, ride, ride, let 'er ride

Just don't fill it all the way.....simple as that. The gas is also coming from a cool underground storage tank and gets put into a warm tank. Can you say expansion ?? You may have to stop an extra mile or earlier...no biggie.

[Joe Nardy]

Thanks ff. This makes sense I guess. I did fill it up right to the top...and I mean the very top. But, this is just the same as I always did with my other cap and it never leaked like this. Only if I put it on the side stand.

How full should I fill it? Is there a visual indicator somewhere I can reference? I don't remember seeing anything in the owners manual or Clymers about how much gas to put in.

I figured put as much gas as possible so I don't have to stop as much

I always fill up on the center stand. Maybe I should fill up on the side stand to make sure I don't over fill.

Ride, ride, ride, let 'er ride

You should only fill the tank to the bottom of the filler tube to allow for expansion.................

Thanks,
Joe

[gbw]

You should only fill the tank to the bottom of the filler tube to allow for expansion...

Thanks Joe - I'll try that.