[txnighthawk]

alright so....I was leaking gas from my drainage tube on my carburetor. I took off my carbs and all floats, pins and needles checked out good. I put my bike back together and its leaking when the petcock is on the "reserve" position and not on the "on" position. Could the petcock cause this problem and not the carbs?

 

[txnighthawk]

I take that back....the carb drain tube is leaking in both the "on" and "reserve" position....can something wrong with the petcock be the reason?

 

[wadenelson]

Take the carbs back apart and try floating each of the suspect floats in a bowl of gasoline. Dunk 'em under and look for bubbles. One of 'em may be holy.

Instead of starting a new thread with each round, just come back to this one and post updates, ok?

You've GOT to find someone local who's got carb rebuilding experience to help you, even if it's lawnmower carbs he's worked on, or Holley double-pumpers. There's a lot to look for, like float level, etc. I can't zoom in on what your problem is from 1000 miles away without being able to look and touch the carbs. I can only throw common suggestions out.

Something like the carb being mis-assembled, so the float is catching on something....no way I could guess that from here....

The bottom line is STILL the float is not coming up and blocking off the flow of petrol into your carb bowl, which is then overflowing.

 

[Dodsfall]

The valve seats in the carb could also not be sealing. I would check the float levels as a first step.

 

[zippywonder]

Yes, a bad petcock will do the same thing. That's what I went through, everyone was insisting that the carb was to blame. I had the carb completely redone but a qualified carb guy and still leaked gas. My petcock was a vacumn fed petcock, turns out that the petcock was bad. Haven't had any trouble since changing out the petcock.

 

[txnighthawk]

Thanks y'all... I'll post an update when I figure it out.

 

[wadenelson]

a bad petcock will do the same thing. ... everyone was insisting that the carb was to blame. I had the carb completely redone by a qualified carb guy and still leaked gas. My petcock was a vacuum fed petcock, turns out that the petcock was bad. Haven't had any trouble since changing out the petcock.

Since it's MY JOB to correct misinformation in the ENTIRE Internet

The ones I've rebuilt were not actually petcocks. (Valves) It's actually a little vacuum operated fuel pump. Vacuum (suction) from the motor sucks on (pulls) on a rubber diaphram and a one way valve allows fuel to flow in behind it from the tank.

When the vacuum goes away..., the rubber diaphragm springs back and pushes the fuel past another one way valve, and out to the carb bowl. (Sometimes there's a little spring in there to help the diaphragm)

So at most the vacuum-actuated petcock is a BACKUP to a float needle/seat that isn't sealing properly. Without vacuum pulses, gas doesn't flow. Problem (apparently) solved.

Factory manuals often refer to it as a fuel "valve" rather than a "pump" but hey, if it walks like a duck, quacks like a duck, and will, when supplied vacuum pulses, pump fuel above the level of the tank...

A lot of MCs for a LONG time have had trouble with carb floats sticking, needles & seats not sealing, (probably due to vibration) and that's why for DECADES riders would TURN OFF their fuel at the tank petcock when they parked the bike. Using a REAL petcock.

A vacuum operated petcock (pump) just adds one more level of defense against your cylinder getting filled with gasoline from a non-properly-working float while the bike is parked.

Repairing the petcock, err, pump, has just covered up your problem with the sticking float. If your float is indeed sticking your float (fuel) level is too high a lot of the time and a certain amount of gas is overflowing and just getting ...wasted. See if your carb has a little glass "inspection" window and check the fuel/float level.

Your sticking float problem may have corrected itself anyway, provided your carb was properly rebuilt, new float needles/seats installed, etc.

Some carbureted bikes overflow excess gas in the bowl onto the ground, others right into the intake where it gets burned, fouls plugs, makes the bike hard to start, etc.

 

[zippywonder]

Mine never leaked gas sitting. Only leaked when running. Did away with the vacumn petcock and went with the regular on/off/res instead of on/prime/reserve. Floats r set to factory spec. Not sticking. Needles r fine. I knew it wad the petcock because I took off the vacumn line from the petcock that goes to the carb and gas was coming out where it shouldnt have. So I am also correct in saying it could be a bad petcock. Carb cant cause a leak if it aint connected.

 

[zippywonder]

And if u go to another forum that is for savages only you will find out that a bad petcock is very common for my particular bike

 

[wadenelson]

If the little rubber diaphragm in the "valve" or "pump" is torn, then fuel can indeed flow, gravity fed, into the carb/motor via the vacuum line.

But if I'm not mistaken, that fuel wouldn't end up in the fuel bowl, or come OUT the fuel bowl overflow, as TXnighthawk describes. The vacuum line normally connects somewhere to the throat of the carb or intake manifold.

Where was your bike leaking gas from? Or was it just flooding the engine?

 

[zippywonder]

I dont know if it actually made it to the bowl as the bike seemed to run like it was starving for fuel when it was flooding out. It would come out the bowl vent tube. I dont know kinda crazy. But whatever. A new type of petcock worked for me. Carb rebuild wasnt wasted mkney as the bike runs better than ever.

 

[txnighthawk]

Hey y'all....just to update...I ended up pulling the carbs off, found an awesome mechanic on craigslist of all places. He cleaned and rebuilt all 4. I put the bike back together now it's a rocket. With only 120 miles or so under my belt, I took a trip with 3 guys. We did 1250 miles in 3 days with an average speed of 50mph through 5 states with only 20 minutes of interstate the whole trip. It was awesome and old nighthawk whipped ass the whole way

 

[wadenelson]

I ended up pulling the carbs off, found an awesome mechanic on craigslist of all places. He cleaned and rebuilt all 4. I put the bike back together now it's a rocket.

For the benefit of other new owners of old bikes out there, I'm gonna open a institutional-sized can of "I TOLD YOU SO!"

>What I suggest for new owners /old bikes having problems is to go ahead and PULL the carbs off yourself, order the rebuild kits, but PAY an old hand to rebuild them for you.

>Most times rebuilding the carbs makes an older machine run like a brand new bike.

Thanks for the update. Ride safe!