[AT] Super A Carb Leak

[Ben Wagner]

On 7/6/2010 9:44 AM, Mike Sloane wrote:
> 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
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Originally, the first time the carb leaked, the float did have a pinhole 
leak.  So the float is brand new, as well as the needle and seat.  The 
only other float trouble I could have would be a tab on the end.  The 
old (probably original) float did not have this little tab, but the new 
one does.  Picture of a float with the tab, though it isn't my style 
float...

http://www.ecrater.com/p/2251405/farmall-abc-340-zenith-carburetor-float#

Does this tab really do anything?  Would it interfere with the 
float/needle sealing properly?  The parts book float does not show this 
tab, but perhaps there is something better about having this tab.

Thanks everyone for all the ideas, and I would enjoy hearing more.
Ben Wagner