PICT 34 carb fuel draining and hydrolocking

[chuck c]

I had an idea. I might learn a useful clue if I let it drain and see at what level it stops. It stopped at the level of the intake port for the accelerator pump. That's where it's going in, how is it getting from there to the throat? Since I have disconnected the accel pump, I could just plug that hole.

 

[joedrum]

fill it back up now that the pump full and see if it leaks more

 

[chuck c]

The pump could have been filled many times by the amount of gas that's gone down that hole.

 

[chuck c]

Carb removed. It was very hard to see but it appears to be coming from the air bypass holes #11 in this diagram. That maze of passages and screws is far beyond my mental ability. Anyone have an idea what might cause this, other than it's a cheap knock-off carb that never worked right from the factory? We need a table-flipping smiley. I think I blew $80 on a POS carb.

 

[slabghost]

11 is passage from air cutoff valve. Is yours not energized? dkl has his hooked up and energized.

 

[Ansimp]

There is a circuit to the accelerator pump in the bottom part of the bowl. You can only empty the bowl with a drain/leak or a check ball/valve not working in the accelerator pump circuit.

 

[chuck c]

slabghost » Sat Oct 29, 2016 7:08 pm[/url]":2fnbgvi1]
11 is passage from air cutoff valve. Is yours not energized? dkl has his hooked up and energized.

Look closer. It's labeled "bypass holes" and they go to screw #9

 

[chuck c]

Ansimp » Sat Oct 29, 2016 8:04 pm[/url]":1g8w025f]
There is a circuit to the accelerator pump in the bottom part of the bowl. You can only empty the bowl with a drain/leak or a check ball/valve not working in the accelerator pump circuit.

I don't quite understand. From what I see the accel circuit is completely separate after it leaves the bowl. How can fuel be getting from the accell pump passage to the "bypass holes" in the throat? Keep in mind I'm not 100% sure that's where the fuel is getting into the throat, but maybe 90%. It's pretty hard to see such a small flow inside the carb throat.

I think I will try plugging the hole to the accel pump in the bowl with a screw. I know the thread size. I can dab on a bit of gasket goo and make a plug that's reversible. If that stops the leak, I'm ridin'.

PS there was a lot of gas pooled in the manifold. I'm glad I designed it to catch liquid. I was very close to adding a drain plug because of this problem. As is, I soaked most of it up with a paper towel and the rest should evaporate overnight.

 

[WalterM817]

My bet is it's coming from the float bowl and siphoning up to the enrichment circuit. The engine would create vacuum to keep the siphon going pretty steady under throttle but the siphon would still exsist as the engine is shut down. It's not streaming .....just a fast drip after shutdown so after it gets down low enough that the weight of the gas in the bowl can't push it up high enough it would stop. Just a theory. The only thing you could do is lower the fuel level which might not give you enough volume in the bowl. Nothing else comes to mind unless you want to drill a vent hole back into the float bowl to break the siphon. Not sure if that would affect anything else but it would let you keep fuel in the bowl until vacuum is applied. Shot in the dark I guess and could be patched with JB weld if it doesn't work.

 

[chuck c]

Forget the accelerator pump circuit for a moment.
Theory: the shut-off valve is trapping fuel in the idle circuits that would otherwise drain away. That trapped fuel is seeping out the bypass holes and creating a siphon that drains the bowl and if the petcock is open, the tank. Those bypass holes are about the same level as the accel pump inlet. It could be just a coincidence that the fuel drained to that level and I'm wrong blaming the accel circuit.

SO the thing to do is remove the cutoff solenoid and plug it. Allow air into those passages and let any fuel drain when the engine is turned off. Siphon is broken, gas stays in bowl. This makes more sense because there is a connection between the bowl and those holes and none (that I can see) to the accel pump passage.

 

[chuck c]

:rant: I removed the cut-off solenoid plugged its hole and the one to the accelerator pump. IT STILL LEAKS. The only way for fuel to get out of the bowl is by the jet. This carb is NFG, I'm not wasting any more time on it. $90 pissed away. Buying another. Spending more this time.

 

[joedrum]

ok chuck ...fuel shut off means just that ....plugging the hole dosnt stop the gas flow ...it just plugs the hole where it was .....the gas will still flow in my opinion

 

[chuck c]

Are you insane? What carb has you EVER seen that leaks a couple of pints and hour down the throat!? Even with the petcock off, the entire fuel bowl drains into one of your cylinders every time you shut it off! Do you really consider that normal operation?

 

[joedrum]

yes i might be insane ...but i also am the owner of hooch ...probably the fastest SCC bike on the planet ...if you have the fuel shut off for the carb ...put it back and hook it up ...it will not drain the bowl anymore ...plain and simple chuck

 

[dan filipi]

The solenoid valve is intended to stop fuel flow when the engine is off to prevent diesaling run-on. Could be fuel is leaking past?

 

[joedrum]

this is what learning your carb is ....so all you vw carb guys need to for sure keep the fuel shut off on carb and hooked up...seems to really effect this carb

 

[chuck c]

joedrum » Sun Oct 30, 2016 2:02 pm[/url]":2onrigi0]
yes i might be insane ...but i also am the owner of hooch ...probably the fastest SCC bike on the planet ...if you have the fuel shut off for the carb ...put it back and hook it up ...it will not drain the bowl anymore ...plain and simple chuck

It WAS on and it WAS hooked up. I posted pictures of the bowl draining WITH that shut off valve in place and working. "Plain and simple" is you're not paying attention to what I'm doing and saying.

 

[chuck c]

dan filipi » Sun Oct 30, 2016 2:06 pm[/url]":346y9xdj]
The solenoid valve is intended to stop fuel flow when the engine is off to prevent diesaling run-on. Could be fuel is leaking past?

Beats me. It works in and out but I have no idea if it's sealing the port like it's supposed to. The working end is metal, I don't see how it can ever fully seal it off.

 

[brianinpa]

Is it possible that the solenoid is defective and it doesn't fully shut off the fuel?

Are you also saying the the carb continues to leak even with the petcock closed? Is the petcock leaking?

 

[joedrum]

could be chuck many think my posts are hard to understand LOL.....were trying to help...a carb is not brain surgery...but it seems to be ...most blame manifolds ..heat ...anything but learning the carb....sounds to me it should be rubber tiped ...dft carb i have was