magical expanding gasoline

[robsGS850]

ok, so, maybe this is related to my earlier post ("Wonky Fuel Gauge") but today after filling my tank, riding it home, then luckily strolling by it a half hour later, there was giant puddle of gas underneath my bike!

It was seeping right out of the gas filler cap, all over my fresh new paintjob.

So, after mopping it up, siphoning some off, loosing more brain cells from the fumes than I can afford to give up, the cap goes back on. And three minutes later gas erupts from under the cap gain! Hey wow, energy crisis solved, magical expanding gasoline!

Seriously, what the ..?

Did the guy who painted my tank clog some kinda... pressure release vent or something?

[SqDancerLynn1]

You over filled the tank, simple

[tkent02]

Gasoline expands. Magic.

[DimitriT]

Had that problem on the 550 on a regular basis. It turns out the P.O. coated the tank
and forgot to clean out a tiny vent hole in the filler neck. Once that hole was cleared
I never again experienced the problem. Too bad it already messed up the old clearcoat
and the pinstriping.

[twiggy2cents]

let me guess you filled it on the center stand then parked it on the side stand? I did that once. it took like 5 coats of wax to pull it back to life

[posplayr]

Been there done that; still have not gotten over it.

[robsGS850]

much thanks for all the advice

my guess is it's the tank liner I put on over the winter... this is the first time i've topped it up since then, though i've filled it even more full many times before the liner without any troubles.

So… whereabouts exactly is that little vent hole? I'm going to go poke around with some wire to unclog it, see if i get lucky

[DimitriT]

much thanks for all the advice

my guess is it's the tank liner I put on over the winter... this is the first time i've topped it up since then, though i've filled it even more full many times before the liner without any troubles.

So… whereabouts exactly is that little vent hole? I'm going to go poke around with some wire to unclog it, see if i get lucky

On the 550 the vent hole is in the filler neck which is the metal tube which extends
into the tank. It's small like the size of the pencil tip. It's purpose is to allow air
trapped outside of the filler neck to vent. If that air doesn't vent and expands or the
gas itself expands, it will force gas up through the neck and out.

[tkent02]

It should be on the right side of the collar, it does not hurt to knock a much bigger hole there.
I usually put about a 1/4" hole as high up as I can get it. Be careful of sparks!

[themess]

Every GS I've seen has the fuel filler offset to the right. The filler is on the top when the bike is on the side stand.

Gasoline expands as it warms. Fuel stored underground can been substantially cooler than outside air. Fill a tank to the brim with cold fuel on the side stand, then park it in warm air on the center stand, and it is easy for the gas to overflow.

Most likely, the gas station isn't far from your home. If you would have ridden ten miles or so, you would have burned up enough to leave some room in the tank for expansion.

[tkent02]

Every GS I've seen has the fuel filler offset to the right.

Haven't seen many GSes?
The caps are about half and half, center or right side.

[themess]

Apparently not as many as I thought I had! Just checked the Gallery. Seems that before 1979, center placement was the rule, and that the gas cap stayed in the center later than that for displacements under 550 cc, and for a few L models. Can't tell for sure, though.

[Killer2600]

Apparently not as many as I thought I had! Just checked the Gallery. Seems that before 1979, center placement was the rule, and that the gas cap stayed in the center later than that for displacements under 550 cc, and for a few L models. Can't tell for sure, though.

That rule doesn't work, my 82 750 has the cap placed in the center.

[tkent02]

'81 1100E, center cap.

[tejasmud]

1985 GS700E center cap.

On the Cali version, the vent tube extends into the tank with some separator inside as well.

Will be interesting doing the POR treatment on this one. Sure don't want to seal it up as well.

Suppose I would be able to tell if I have magical gas afterwards.