[AT] Easier to Start?

[Mike Sloane]

I am watching this thread with interest. If I may, there is one other 
common reason for needing to run with the choke: a vacuum leak between 
the carburetor and the head. Even a pinhole in the manifold casting or a 
slight leak around one of the gaskets will cause the fuel/air mixture to 
be lean and need the choke to compensate by making the mixture leaving 
the carburetor richer. I have suggested in previous messages that an 
easy way to find a vacuum leak is to use a propane torch. Crack the 
valve open but don't light it, then move the head slowly up from the 
carburetor to the head and all around the intake manifold while the 
engine is idling. If there is a vacuum leak, it will suck the raw 
propane into the combustion chambers, and the engine will speed up. You 
have to move relatively slowly, as it takes a second for the propane to 
be pulled into the combustion chambers, especially at idle speed. (You 
don't need to have the valve wide open - it only takes a little propane 
to provide the needed indication, and it won't hurt the engine.)

Mike

On 7/16/2012 8:50 AM, Ben Wagner wrote:
> Hi Charlie,
>
> Thank you for your very detailed breakdown on cleaning my carb.  I
> actually hesitate to tear back into it, since I have taken it apart
> three times since the restoration in hopes of finding the elusive
> problem.  I have eliminated most recently:
>
> ~fuel flow
> ~clogged/constricted main jet
> ~trash around the float needle/seat
> ~trash in the passages
>
> If my carb is indeed clean, and assuming my air filter is working
> properly, what other problems might I have to cause the engine to only
> run on half choke?
>
> On another note, on my 1945 A, I have a "needle valve main jet
> adjustment" screw that allows me to adjust the mixture.  It screws into
> the main jet.  In the Super A parts book, the screw is listed, but it is
> listed as only available on kerosine/distillate engines. I'm assuming,
> then, that it is not needed for a gasoline engine, correct?
>
> Thanks to everyone for their help so far!
>
> Ben Wagner
>