Gas leaking from overflow

since my petcock is obviously leaking through, is it possible that the float is not wrong? could it be that the angle that the bike sits at on the kickstand is enough to make it overflow with the bit of leak-through from the petcock?

Do they still leak when you are sitting on it with the engine running ?

does not leak at all with the engine running.

its only 7:30 am here in Chicago and I haven't slept all night because this is bugging me. it drives me nuts because i have no room to actually do the work myself any more, and any shops wont be open til about 10 and most likely they will tell me that it will be a week or more before they can get me an appointment.

ok. so after reading some more on other threads i feel a bit stupid, but equally as stumped. i went down to the garage and took a pic of the petcock because i didnt realize that some were vacuum operated and some where just manual valves.

when i picked up the bike, the guy who built it told me that the off position is what i now see is actually "prime" position.



so, i put it in the "on" position to see if the leak would eventually stop after running it for a few minutes to clear out the float bowl as much as i could.

i do not see position for "off" at all.

either way, i would imaging that the floats are still stuck open to some degree or the gas wouldn't have been leaking out any way.

here is a full pic of the bike, just in case anyone wanted to see it.

Vacuum operated petcock receives vacuum from a running engine via a nipple fitting on the carb or carb holder from which fitting a vacuum hose runs to the petcock.

When there's no vacuum being supplied by a running engine, there's a rubber diaphragm, o-ring and spring inside the petcock that prevents fuel flow in the ON or RES (reserve) position. When the engine isn't running, both ON and RES positions are the same as OFF. This design allows us retards to ignore any need to shut off the petcock when parking the bike.

PRI (prime) position by-passes the rubber diaphragm, o-ring and spring, permitting fuel flow without needing any vacuum. Same as a manual (non-vacuum) petcock in ON or RES position. For example, PRI could be used to fill the carb float bowls when the engine isn't running (i.e., when there's no vacuum being supplied to the petcock).

Good Luck!

Patton wrote: Vacuum operated petcock receives vacuum from a running engine via a nipple fitting on the carb or carb holder from which fitting a vacuum hose runs to the petcock.

When there's no vacuum being supplied by a running engine, there's a rubber diaphragm, o-ring and spring inside the petcock that prevents fuel flow in the ON or RES (reserve) position. When the engine isn't running, both ON and RES positions are the same as OFF. This design allows us retards to ignore any need to shut off the petcock when parking the bike.

PRI (prime) position by-passes the rubber diaphragm, o-ring and spring, permitting fuel flow without needing any vacuum. Same as a manual (non-vacuum) petcock in ON or RES position. For example, PRI could be used to fill the carb float bowls when the engine isn't running (i.e., when there's no vacuum being supplied to the petcock).

Good Luck!

Thanks for that explanation Patton. Best one I have been able to find thus far.

One question to add to this....

Should the float in the bowl not still keep any gas from overflowing even with the petcock in the "prime" position?



*Update*

Instead of letting the bike sit for a while, I decided to give it a ride that is a loop of about 40 blocks from my home. I couldn't get the bike to stay running in the "on" position so I switched to "res" thinking that I could make it the twenty blocks down to the gas station. Wrong!!! I must have leaked out a lot more gas over the last two days that I realized, because I got about 12 blocks and ran out of gas. Had to walk the last 8 to the gas station ....in the rain. Yes, it started raining about 2 minutes after the bike stopped.

Now that its gassed back up I made it home alright, but the engine is sputtering quite a bit while accelerating and while holding the throttle steady. I assume that this is a fuel delivery issue, and probably has something to do with the sludge that is probably holding the float out of position. Any thoughts?

AjKZBobber wrote: ...Should the float in the bowl not still keep any gas from overflowing even with the petcock in the "prime" position?

Yes, the float valve -- needle and seat -- is supposed to operate efficiently enough to prevent gravity-fed fuel flow into the bowl when the valve is in its closed position. In other words, the pointed tip of the float needle is supposed to interface perfectly with the orifice in the seat, whereby the float valve is held closed by buoyancy of the float (the float tang presses against the float needle which presses the needle's pointed tip into the seat orifice).

...engine is sputtering quite a bit while accelerating and while holding the throttle steady. I assume that this is a fuel delivery issue, and probably has something to do with the sludge that is probably holding the float out of position. Any thoughts?

Could result from a variety of conditions. But imho doesn't likely result from "sludge that is probably holding the float out of position."

Good Fortune!

Just remember if there is ANY trash, rust etc. in your tank it will sit in the very bottom of the tank. With this being said when you run on reserve it sucks that trash right into your cards which is a logical explanation on why your bike is now running different. A clean tank is crucial to keeping the carbs clean in the circuits.

I try to never hit reserve because of this reason, I will manually purge the foreign materials out of the tank at home, that way I am not calling for a truck/trailer because only half the carbs are working properly. Ask me how I know. :S

Also keep in mind a leaking petcock can fill your crankcase with gasoline which will ruin the properties of the motor oil. I have pulled out over one and a half quarts of fuel out of my crank case before. Check your oil level and see if it is on the high side if so change your oil before you start it.


Z1 Enterprises sells affordable rebuild kits. I would also recommend an inline filter between the petcock and the carbs.

AjKZBobber wrote: since my petcock is obviously leaking through, is it possible that the float is not wrong? could it be that the angle that the bike sits at on the kickstand is enough to make it overflow with the bit of leak-through from the petcock?

If the needle valves/seats in the carbs are good (and adjusted right) the carbs will not leak even if the petcock is left on. I know because I forget to turn it off sometimes and there is no observable leakage.

bluej58 wrote: Do they still leak when you are sitting on it with the engine running ?

They won't because the gas flow being used to run is more than the leakage rate.

AjKZBobber wrote: either way, i would imaging that the floats are still stuck open to some degree or the gas wouldn't have been leaking out any way.

nope. Even with the float all the way up, pressing the needle into the seat as hard as it can, there can still be leakage if the needle tip is not a perfect fit to the opening in the seat. Gravity will push the gas through and out the overflow.

ALSO: the seats are brass and they oxidize over time, and then the steel tip does not have a good seal anymore. That's why I used to do a needle tip/seat polish every six months as general maintenance. That way I never had a flooding problem.

are there any tutorials with pictures on how to remove the float bowls, and what to look for once I have them removed. I have heard that they can be removed without taking out the whole carb, but the manual I just found does not show that.

thanks again to everyone who has chimed in on this issue. i cant tell you all how much i appreciate the help.