Gas Overflow

[01Silverado]

I have a manual valve on my gas tank, instead of a fuel petcock. When I start the bike and open the valve, gas starts dripping everwhere. Should the float and needle valves in the carb bowls completly stop the fuel flow?

 

[DanTheMan]

Yes and no. Without having the vacuum operated petcock your tank is providing fuel to the carbs 24/7 just like putting a petcock on prime. Throw out your manual valve and put a proper petcock on it.
The float valves will stop flow normally (if the float valves aren't all gummed up and sticking open) when the engine is running with a normal petcock on in the run or reserve position.

 

[81gs1100]

Yes, clean and correctly adjusted needle and seat will stop the flow completly for however long you leave your manual valve open. Unless the tank is a 55 gallon tank and full there wouldn't be enough pressure to push gas past the seats.

So if you are leaking gas, recheck the float level, needle tips, seat, and the most over looked part, the O-ring between the seat and the carb. The best thing to do is to get a pop-off valve checker and with the carbs upside down, pump air into the fuel inlet and see if they are holding pressure or if there are leaks. Spraying WD-40 on and around the needles and seats will help locate leaks and provide a good seal.

You wont see it holding back 10 psi or anything, but if you can hold 2psi for a minute or so you should be fine.

 

[81gs1100]

Yes and no. Without having the vacuum operated petcock your tank is providing fuel to the carbs 24/7 just like putting a petcock on prime. Throw out your manual valve and put a proper petcock on it.
The float valves will stop flow normally (if the float valves aren't all gummed up and sticking open) when the engine is running with a normal petcock on in the run or reserve position.

While the engine is running there is no difference in a manual petcock, or a vacumm operated petcock, both will flow constant while the engine is running. And as long as the manual is shut off when the bike it turned off, there is no problems.

 

[01Silverado]

Thanks 81GS, that is what I was wondering. Illl start pulling the carbs off.

 

[Nessism]

Thanks 81GS, that is what I was wondering. Illl start pulling the carbs off.

On a recent carb rebuild I set the carbs up in a vice so they could be held horizontal and then I used a funnel to feed fuel into the carbs until I was satisfied that the float needles would shut off the flow of gas like they should. It's a little bit of extra work do to this sort of thing but worth it in peace of mind.

 

[streetfighters]

Just an FYI, I spun a non-welded Suzuki GS1100 crankshaft in my 82 Kitty due to a leaking float valve on the left outboard ( #1) cyl. Parked the bike for a week and left the fuel petcock on. The cyl. slowly filled enough to create a " hydraulic lock" on that cyl. When I hit the starter button the cyl. pressure was distributed unevenly across the crank and I lost a few degrees on the left crank end. The engine ran pretty goofy too! $700.00 later and I had a shiny new Falicon welded, balanced, polished and shot-peened crank w/new bearings. So, then I had to buy a " big bore" kit, and then the carbs. were too small, then the exhaust did not have enough flow, then the head needed better flow, then the ignition was too weak -------ARRRGGGGGGHHHH!. Lessons learned the hard way. Should'a shut the fuel off, eh?
streetfighters

 

[Nessism]

Just an FYI, I spun a non-welded Suzuki GS1100 crankshaft in my 82 Kitty due to a leaking float valve on the left outboard ( #1) cyl. Parked the bike for a week and left the fuel petcock on. The cyl. slowly filled enough to create a " hydraulic lock" on that cyl. When I hit the starter button the cyl. pressure was distributed unevenly across the crank and I lost a few degrees on the left crank end. The engine ran pretty goofy too! $700.00 later and I had a shiny new Falicon welded, balanced, polished and shot-peened crank w/new bearings. So, then I had to buy a " big bore" kit, and then the carbs. were too small, then the exhaust did not have enough flow, then the head needed better flow, then the ignition was too weak -------ARRRGGGGGGHHHH!. Lessons learned the hard way. Should'a shut the fuel off, eh?
streetfighters

Sure you didn't leave that petcock On on purpose (looking for an excuse)?:lol: