Where's my gas disappearing in float bowl?

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Nov 22, 2004
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I don't get it, before my carb rebuild my gas was disappearing from the float bowl and really thought that rebuilding it would cure this problem. I was maticulious in cleaning, soaked in carb dip for a few days, dipped in mineral spirits 3 times blowing with compressed air numerous times. So where could it be going? Does't appear to be leaking out the jet access bolts, doesn't appear to be leaking out the sight glass, so that only leaves draining out the jets them selves or the power valve. But how could it be possible it's going up hill to drain out a venturi? I'm positive my vent tubes are clear, so I don't see how any pressure could be building up. That much gas couldn't evaporate in 24hrs could it?
 

folsom50

 
 
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Mine does the exact same thing, even after the I installed a carb kit. I get awesome milage now and my 40 runs great, so I just quit trying to figure it out.
 
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My aisen carbs, 1bbl and 2 bbl "nonUSA", do not empty their float bowls in 24 hours by any means, FWIW. Might go down to 1/2 in a week, at most. What year are we talking about?
 

surfpig

The Anti-Tech
 
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Is it a California model with that ridiculous thermonuclear reactor exhaust manifold? :mad: That'll sure explain it...

nial
 

Landpimp

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neither of my 1 barels do either, unless they sit for a while. Not sure how long it tak s for my 81+ to drain or whatever.......but its more than a day.

IDave said:
My aisen carbs, 1bbl and 2 bbl "nonUSA", do not empty their float bowls in 24 hours by any means, FWIW. Might go down to 1/2 in a week, at most. What year are we talking about?
 

folsom50

 
 
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IDave said:
My aisen carbs, 1bbl and 2 bbl "nonUSA", do not empty their float bowls in 24 hours by any means, FWIW. Might go down to 1/2 in a week, at most. What year are we talking about?
Mine's a desmogged '78. If the engine is hot, I have about 24 hrs before the fuel is below the window. Otherwise it's about 3 days.
 

Pin_Head

 
 
 
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It is most likely evaporating, but it can also siphon out of the idle fuel circuit under the unusual circumstances of if the air vents are plugged and the idle fuel cut off solenoid doesn't seal tightly. It could also siphon out of the secondary transition fuel circuit slot if its air vent is plugged. It is easy to check because it will leave a puddle of gas in the bottom of the manifold that you can see with the throttle open with a flashlight. My '76 with thermonuclear reactor manifold takes a couple weeks sitting to evaporate. It is bad to continuously let it sit like this and evaporate as it tends to build up deposits that eventually plug the air vents and jets.
 
Last edited:
Joined
Nov 22, 2004
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139
Thanks everyone. I'm wondering about the fuel cut solenoid, I noticed it had a very small o'ring at the end. I noticed in my kit there was a small o'ring but it didn't look like it matched the one on the fuel cut solenoid so I didn't use it. Is that where it's supposed to go?
 
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Nov 22, 2004
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Update: I've discovered when the fuel drains it's puddeling up on the floor of my intake. I've taken the airhorn off twice now and making sure the breathers for the primary and secondary slow jets and the venturi breathers are not clogged and air passes freely but the fuel still drains out overnight. Any other ideas? I've studied the carb diagram numerous times and just can't see how it's draining if it's not siphoning. When I rebuilt it I noticed there were no gaskets on either side of the spacer between the base and the carb body but don't see how that could impact this.
 
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Old post, did you figure it out? I have a 1970 Aisan D40 1bbl and I desperately need a new brass float. When you mentioned that it was pooling on the floor of the intake I could identify with that. Mine does that because the float leaks, fills somewhat with fluid which allows it to drop, raise the fuel level and it runs all over the place inside and out and of course when I pull the carburetor the intake manifold is wet.
 

JohnnyC

Long ago TLCA# 2231
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did you try soldering to plug where its leaking?

should be able to find a video on youtube
 

Pin_Head

 
 
 
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Fuel can siphon out of the bowl through the idle circuit. The idle port is below the level of fuel in the bowl. There is an air vent that is supposed to prevent siphoning by breaking the vacuum. Fuel could also creep over the top by capillary action. This could happen if the fuel passage is corroded and rough allowing surface tension to cause the fuel to creep over the top.
 
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The steel stamping on my pressure plate spells it Aisan.

Yes, I have soldered it, four times now. By using my heat shrink tubing heat gun I can get the brass hot enough that my soldering iron provides good flow. I had one spot on the side of the bowl that would steam and have soldered it twice now. The last time I applied J-B Weld over the seams, the spot on the side and the vent hole. It was a seam leaking. I will presume that when I heat the unit up and the gasoline is forced out that where it comes out is where it is going in. So I cleared the vent hole, heated until "dry", put some lacquer thinner in the vent hole and swished that around, drained it, heated to force dry and then went around all my seams again. Once that was done I sanded it, cleaned with lacquer thinner and applied the J-B Weld. Have to wait a minimum of 15 hours for cure.
 
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