Why does my Yamaha EF1000 Generator leak gas out of the gas tank vent hose which comes out of the fuel petcock (on/off valve)? It does it when its not running but and even a few moments after it has ran, and also when it is running sometimes it will leak but just a little bit? the carb is clean and vent/overflow line from carb is perfect and not restricted and never leaks, so the carb is not overflowing!, and the engine always starts and runs great! but i keep loosing fuel? But a note, after it sits not running and/or after it has ran, you can remove gas cap and hear pressure release! Any answers would be appreciated!, Thanx A Million

Your fast on the draw with the answers, i like that and thank you, However the petcock on the tank does not use a diaphragm setup, which i know what you are refering to from my motorcycle experiance, But it uses just a basic type on/off petcock with the little rubber valve inside and normal cover, control lever with o-ring with the two screws and that bolts to the bottom of the fuel tank but does have a vent hose running from it along with the fuel line on the opposite side, i am starting to think it is that rubber valve in the petcock that rotates when the petcock lever is rotated from off to on that is coming apart or has hardened and not opening the vent part or something when valve in petcock is closed which is activated by the control slide lever which is three position off/run/choke and when the control slide lever is in the off position it moves a lever and turns the petckock to the off position shutting off fuel, on run and choke it turns the petcock on allowing fuel flow! but to me shouldnt the tank be vented regardless of fuel valve position? if you look up the parts diagram on yamaha-motors website you can see the petcock and parts, i guess it looks like i will just have to take it all apart and see whats going on! What do you think? Your fast on the draw with the answers, i like that and thank you, However the petcock on the tank does not use a diaphragm setup, which i know what you are refering to from my motorcycle experiance, But it uses just a basic type on/off petcock with the little rubber valve inside and normal cover, control lever with o-ring with the two screws and that bolts to the bottom of the fuel tank but does have a vent hose running from it along with the fuel line on the opposite side, i am starting to think it is that rubber valve in the petcock that rotates when the petcock lever is rotated from off to on that is coming apart or has hardened and not opening the vent part or something when valve in petcock is closed which is activated by the control slide lever which is three position off/run/choke and when the control slide lever is in the off position it moves a lever and turns the petckock to the off position shutting off fuel, on run and choke it turns the petcock on allowing fuel flow! but to me shouldnt the tank be vented regardless of fuel valve position? if you look up the parts diagram on yamaha-motors website you can see the petcock and parts, i guess it looks like i will just have to take it all apart and see whats going on! What do you think?

Yes, I agree that there should be a tank vent, and that it is plugged. Did you try running the engine with the tank cap cracked? You may have to disassemble the petcock and check to see if there is internal damage. If so, the repair costs will be minor.

Good luck!

--W/D-- Yes, I agree that there should be a tank vent, and that it is plugged. Did you try running the engine with the tank cap cracked? You may have to disassemble the petcock and check to see if there is internal damage. If so, the repair costs will be minor. Good luck! --W/D--