[AT] Super A Carb Leak

[Mike Sloane]

Well, yes, your tank fuel tap/trap *should* shut the fuel completely 
off, so you need to address that. They do get old and worn over time and 
eventually need to be replaced. If the handle turns easily, then you 
need to think that maybe you need to do something. It is possible to 
tighten up on the gland nuts, but I have never had a lot of luck with that.

But, even with a wide open fuel trap, you should not be seeing a leak 
from the float chamber. If the needle and seat are free of debris and in 
good shape, the most likely culprits are either 1. a leaky float or 2. 
the float is binding on the side of the chamber.

A leaky float is easy enough to check - submerge it into a container of 
hot water (it doesn't have to be boiling but it does have to be hot 
enough to heat up the air in the float), and you will see bubbles 
escaping from any pinholes or cracks. A brass float is easy enough to 
solder, but you have to do it carefully - too much heat will only make 
things worse. A binding float is harder to diagnose and fix, but make 
sure that that the hinge part and the pin are very clean for starters. 
If you take the carburetor off and turn it upside down, you should hear 
the float move from one position to the next. If you can't hear that, or 
if you hear any scraping, then you will have to try to see where the 
problem is. (I rig up a hose and try to blow air in when the carburetor 
is inverted, but that isn't much of a real test.) I am sure that others 
will have other (and perhaps better) suggestions.

Mike

On 7/6/2010 8:48 AM, Ben Wagner wrote:
> Hello,
>
> My Zenith 11115 Carburetor is leaking gas from the hole/drain in the
> choke passage.  The carb leaked after I rebuilt the engine, and I
> replaced the float and the needle valve.  That seemed to fix the leak
> until I ran it.  Once I killed the engine, it began to leak after about
> an hour.  And yes, the fuel is shut off, though my shutoff valve does
> not completely seal, allowing a little dribble from the gas tank into
> the fuel line.
>
> So what do I need to do?  Should I replace the the fuel shutoff valve?
> Even if the shutoff drips into the fuel line, the float/needle should
> stop the gas from getting into the carb, right?  The only other option I
> can think of is that my float is not adjusted correctly, and that would
> change the bowl level, which could perhaps allow an overflow into the
> choke passage?
>
> Thanks in advance for your replies.
> Ben Wagner
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