Carburetor Problem

[HANKTHELANK]

I've recently replaced a seized Atomic 4 with one that is in good running condition. When I run the engine I've noticed a very small resedue of fuel developing on the air intake side of the carburetor. The scavenge tube on this particular carburetor has been removed and the opening has been plugged shut. I originally thought that the fuel leak might have been caused by the needle valve or the float sticking, so I took it apart and everything seems to be fine. So i replaced this carburetor with another. I was unable, due to space constraints and the inflexibility of the copper scavenge tube, to attach the scavenge tube at the flange. When I ran the engine, ALOT of fuel developed in the air intake, and actually started to drip under the engine. I am not sure why this is. Again I took apart the carburetor and the needle valve seems to be closing the orifice properly. Again, could this happen because of the scavenge tube not being attached? Unfortunately on this carburetor the idle screw is seized. But since it had been the original carburetor, I assume that it was set in the proper position. Any help with this problem would be great.

Cheers,

Hank

[Don Moyer]

Hank,

Two thoughts:

1) The fuel collecting in the bottom of the carburetor throat is almost
assuredly resulting from a defective or dirty float valve needle and seat.
With no more than a new float valve costs, I think I'd replace it, given
your recent history of problems, but I'd also install an inline polishing
filter between the fuel pump and carburetor. To be absolutely certain that
you'll be free of the problem, I recommend you take a bluntly pointed 3/16"
wooden dowel rod and work it round and round hard against the seat in the
float valve (even a new one) to be sure the edge of the hole in the seat is
nicely polished and free of any sharp or irregular edge.

2) I recommend going back to the carburetor (or at least the upper housing
of the carburetor) which does not have a seized idle mixture screw. There's
no guarantee that you can rely on an idle mixture adjustment to hold for
more than a season or so, let alone for a decade or more. When you
reinstall a new scavenge tube, you'll have to reset the idle mixture at that
time in any case.

Don