Fuel Leak- Pours out of vent hose

[vermin]

Hello,

So, I bought an '89 FJ a few months ago. The tank had some rust, so I immediately took it to my local shop and they cleaned and coated the inside of the tank. Also the bike was lowered, so I had the shop put a very slight bend in my side stand to improve lean angle. Anyway, on my way home from the shop I filled up the gas tank. When I parked the bike and set it on the side stand, gas came pouring out of the vent hose. A lot of gas came out. I put the bike on the center stand and siphoned about a gallon out of the tank, and the leak stopped.

So,

I don't believe that the new inner coating has anything to do with the leak, but maybe it does sometimes?

I don't believe that the lean angle should cause a leak either.

My hunch is that there is some kind of check valve in the cap assembly that is broken, and I need to replace part # 21 http://www.missionmotorcycles.com/fiche_image_popup.asp?fveh=315&section=12951&year=1989&make=YAMAHA&category=Motorcycles&dc=3306&name=FUEL+TANK+%28NON%2DCALIFORNIA+MODEL%29

Anyone had this problem? Ideas?

Thanks,

-Chris

[FJmonkey]

Are you sure what vent hose the gas came from? The carbs also have vent tubes that act as over flow drains when the floats/needles get stuck and gas keeps flowing into one of the carb bowls. Did the leaking continue after getting on the center stand? Maybe you worked the needle/float loose from the rocking motion. Did you replace the fuel filter after the tank repair? A crappy filter will let some dirt get by and keep a needle on the floats from sealing.

Assuming that you were on the side when you filled up and had the leak on the side stand, did you fill it really full? Heat from the engine would cause some expansion. Was it a short ride from the gas station? I am thinking that warm engine/cold gas (expansion as gas warms up), very full tank, short ride (minimal loss of volume)....Or, filling up on center stand, short ride home and parking on the side stand might do it as well. Just my two cents.

[vermin]

Yeah, it was definitely coming out of the vent tube. I like your warm engine/cold gas theory. The bike is pieces right now. So, I just took the gas tank, 1/2 full of sta-bil'ed gas, and held it most every position except upside down, and there was no leak (maybe I should have done this before posting!). Thanks for the input.

-Chris

[markmartin]

Or, filling up on center stand, short ride home and parking on the side stand might do it as well. Just my two cents.

I proved this theory last summer. Gas came pouring out of what I'm assuming was the vent hose.  Now I fill up with the bike on the side stand.

[FJmonkey]

Or, filling up on center stand, short ride home and parking on the side stand might do it as well. Just my two cents.

I proved this theory last summer. Gas came pouring out of what I'm assuming was the vent hose.  Now I fill up with the bike on the side stand.

That is why I asked, I only fill on the center stand if I am out bound on a slab ride to get them few extra miles on the tank. Now its only side stand fill ups as I stick to the twisty fun roads here in SoCal. No more Iron Butt rides for me, been there, done that. Its all fun and games till your legs and butt go numb, have to stop somewhere and just fall over cuz your legs don't work. Never actually did that but did get so cold I could not turn the key off or remove my helmet when I stopped for gas and coffee. "Whats that guy on the bike doing just sitting in the parking lot? Doesn't he know its cold out there?"

[richardphillips6208]

G'day,

I had the same problem when I first picked up my '88 fj from a mate. It had been on the side stand for months and the float needles had seized open. Stripped the carbs, cleaned out the whole system and fixed the problem.
Just my two pence worth.

Richard

[fastmayor]

I am having the same problems and the gas will leak out until it is at the 1/4 area.  Its leaking out the hose that comes right off the tank and gets routed down through the frame and leaks onto the ground. i have disassembled the gas tank lid and cleaned it.  The real bad thing about the whole thing is that i plugged the vent hose first time it happened then it leaked out the gas lid and ruined my tank. is this the same exact prob you had?  the bike runs A1...just 1/4 of a tank at a time.   Any help?