Where did all my gas go?

[Watevaman]

 Background: about mid-October I brought my bike home for storage since it was getting too cold at school for me to ride a lot. Filled it with gas, added Stabil as needed, shut off tank petcock, ran the carbs dry. Now, this past weekend was really nice temperature wise so I took it for a ride on Saturday. I put it away, made sure the petcock wasn't on prime, and let it be because the temperature was too damn cold. I think it was Xmas eve when I went into the shed to get something and it reeked of gas. Looked under the bike and the wood was soaked with gas, but I was busy so I had to leave it alone for now. Later that night I put some cardboard under the bike to see where it was dripping and it looks to be pooling from around the kickstand.

I just got out to shut the tank petcock off and it's pretty much for nothing as my half full tank of gas is now empty (as in, it's pretty much dry). The float bowl drain screws are tight and all my fuel hoses are clamped. There's no real trail for me to follow, but it looks like it might have come out of the nipple on the bottom of the gas tank where I guess the vent hose should attach. Doesn't this hose attach to a "bubble" around the gas tank and then vent out of the gas cap? The front of the carbs are a bit wet/dirty around where they attach to the intake (?) but I don't know if that's gas or oil or just grime build up.

Anyone have any ideas? What's fooling me is that it was fine while sitting and I don't recall doing anything on the ride that might've messed up something. I'm wondering if maybe a hole rusted in the tank and it all leaked out of the vent hole.

[mustangGT90210]

Pull your air box. I bet there's gas in the bottom of it. If so then your carbs overflowed. This can be caused by a sticking float needle, float heights too high, or your petcocks not functional properly. Since you say the tank petcock was on, I'd be willing to bet your frame petcock is no longer properly working

[Watevaman]

 Hmm, I'll definitely check that out. I have a K&N lunchbox so there's no airbox, but I can give it a smell and also test the frame petcock since I've gotta do work anyway.

[adidasguy]

If the frame petcock is dirty, those are easy to clean. Take off. Remove metal clip  that holds things in. Clean. Replace parts making sure you get the lever on correctly. 5 minutes tops then good as new. Be careful you don't poke a hole in the vacuum diaphragm.
No need to and DO NOT remove the back of it. That's just the vacuum and removing it will probably destroy it.

[Watevaman]

 And if I wanted to replace it with a new one? Maybe one that just had on/off/reserve instead of a vacuum operation, what kind of model petcocks would I be looking at?

And I'm also assuming my floats are fine, as the last time they leaked open was when I ended up getting gas in the oil, which isn't the case this time.

[Suzuki Stevo]

Notice the "Arrow" on petcock is not on short end of handle??

[adidasguy]

And if I wanted to replace it with a new one? Maybe one that just had on/off/reserve instead of a vacuum operation, what kind of model petcocks would I be looking at?

And I'm also assuming my floats are fine, as the last time they leaked open was when I ended up getting gas in the oil, which isn't the case this time.

Why replace with a non-vacuum one? What purpose does that serve? Clean it or get a replacement IF you KNOW that it is dirty. However dirty usually causes fuel starvation.

WHERE DID THE GAS GO? Even if a petcock did not shut off the fuel, it will not go anywhere because the float needles in the carbs stop the flow of fuel. They are what control the gas and let it in, and keep it from overflowing.

You assume the float needles are OK, but they could have stuck open just a little.

You might have a gas leak in the tank or the tank petcock. Tank petcocks can leak because they are rarely ever shut off. When they are, the o-ring is stuck and cracks causing a small leak. That is easy to fix: just replace the o-ring. Did you turn the tank petcock off when you stored the bike?

To see if gas is leaking anywhere, fill up the tank and baby powder the fuel lines and bottom of the tank and the carbs. Wait a day or two. Look for signs of gas.

[dinkydonuts]

And if I wanted to replace it with a new one? Maybe one that just had on/off/reserve instead of a vacuum operation, what kind of model petcocks would I be looking at?

And I'm also assuming my floats are fine, as the last time they leaked open was when I ended up getting gas in the oil, which isn't the case this time.

I 2nd adidasguy in the thought that the frame petcock on these bikes rarely go bad. They can be serviced minimally and will still function. When I last had mine apart, I stretched the spring a bit so that the ON position wasn't letting ANY fuel get by.

How old are your fuel lines? Are you using the factory hose clamps?

[radodrill]

Most petcocks are vacuum operated anyways as an extra safety; in case the needle valve is stuck open, the petcock will only allow fuel to flow when the engine is running or when the petcock is set to prime.

[Watevaman]

 Yeah, adidas, I did shut off the tank petcock when storing. Fuel lines are less than a year old, clamps are the ones that go around and you screw them to tighten the clamp. The reason for getting a new petcock would be that I'm 100% certain there's not going to be any fuel flow.

And yes, Suzuki Stevo, I know which way the arrow is. However, on mine, one of the POs did something with the frame petcock label plate which means it's reversed, so my short end points to the ON. I know this because I had fuel problems when I first got the bike.

I'm going to try and source the problem this weekend.

[adidasguy]

Yeah, adidas, I did shut off the tank petcock when storing. Fuel lines are less than a year old, clamps are the ones that go around and you screw them to tighten the clamp. The reason for getting a new petcock would be that I'm 100% certain there's not going to be any fuel flow.

And yes, Suzuki Stevo, I know which way the arrow is. However, on mine, one of the POs did something with the frame petcock label plate which means it's reversed, so my short end points to the ON. I know this because I had fuel problems when I first got the bike.

So the tank petcock o-ring might be the slow drip all winter. My vote goes for that o-ring.

The metal clip for the frame petcock can easily be put on upside down. I don't see the need to try for something different and why you feel 100% there will be no fuel flow. You had fuel flow before. Simply clean the frame petcock or at least pop the clip and put it on the right way.

If you're dead set on changing the frame petcock, buy a new one. About$50. Get the right one for your frame: 1989-2000 or 2001+
A new tank petcock is about $35. That is the same for all models of GS500.

[Watevaman]

 I'm not sure what constitutes a slow drip, but it emptied my gas tank with at least 2.5 gallons in half a week. It wasn't leaking at all when I took it out of storage.

But as I said, I'll take a look at both petcocks.

[adidasguy]

Be sure air box dry.
Clean bike and be sure all is dry.
Baby powder the hell out of it.
Put 2 gallons gas in the tank.
Watch FamilyGuy while waiting for signs of gas in the powder. It may take a day so plan a marathon of us censored episodes.
See where gas comes from. Post pictures. Fix the leak.

Leak could be anywhere and maybe a seam around the tank rusted open so powder the underside of the tank, too.

Watch the tank overflow drain. It goes through the tank from the gas cap area. You will lose gas if it developed a crack inside the tank.  I suppose that could happen if it got full of water and didn't drain due to pinched hose. If it froze, it might crack the tube inside the tank so make sure the drain hose is working by putting water around the gas hole and letting it drain out.

[Watevaman]

 Ok I have the tank off. Set it up between two little tables and filled it with water, opened the tank petcock and what's strange is there's not that much of anything coming out. It's more like a dribble than a flow. Is this because I used water and not gas?

Also put a little water around the cap and saw it dripping out of the overflow nipple on the bottom of the tank.

Hoses had gas in them when I removed them to take the tank off.

Moving on to the frame petcock now.

EDIT: Nevermind, the water flows a little better if I jostle it but it only lasts a few seconds on average. Thinking something might be blocking flow out of the gas tank so I'll take a look.

EDIT 2: Just took the tank petcock off. The filter and stuff is pretty clean. Inside of the tank itself is a little rusty but no deposits at the bottom or anything. I removed the clip as well from the petcock and the black o-ring is pretty well worn. I guess I'll try and fix that. Is that singular o-ring available anywhere and if not does anyone know the size so I can pick one up?



#10 in that picture looks good, so I assume it's ok if I don't replace it?

[radodrill]

Ok I have the tank off. Set it up between two little tables and filled it with water, opened the tank petcock and what's strange is there's not that much of anything coming out. It's more like a dribble than a flow. Is this because I used water and not gas?

Have you checked with the fuel cap open?

[adidasguy]

Water has much more surface tension than gasoline.
The filter screen in the tank is very fine. I think water will not flow through as fast as gasoline.

[Watevaman]

 Yeah that explains it. Not concerned too much since it flowed fine with a bit of a jostle.

Does anyone know if you can buy that o-ring for the tank petcock by itself? No way am I buying a whole new petcock.

[dinkydonuts]

Yeah that explains it. Not concerned too much since it flowed fine with a bit of a jostle.

Does anyone know if you can buy that o-ring for the tank petcock by itself? No way am I buying a whole new petcock.

You can usually find an assortment of o-rings for $10 that will last you a lifetime at any auto parts store. Just find one close enough and stretch it to fit.

[adidasguy]

Yeah that explains it. Not concerned too much since it flowed fine with a bit of a jostle.

Does anyone know if you can buy that o-ring for the tank petcock by itself? No way am I buying a whole new petcock.

Go to hardware store and get an o-ring that is nitrile or other fuel proof material.

[Watevaman]

 Just wanted to bump this and say thanks. Turns out my problem was actually with the fuel hose itself. I guess the ON hose at the tank had enough of the clamp and didn't hold anymore. Replaced the fuel hoses and it seems all is good. Letting it sit overnight and hopefully I won't wake up to a pool of gas on the floor.

However, I did get a chance to replace some stuff that definitely needed it. That o-ring in the tank petcock was shot along with the bolts and washers holding the assembly in the tank. Also took a look at the frame petcock and it seemed just fine.