[Ron in Quincy]

I found, at least with the Zenith, that for a long time A parts dealers were advertising " install the gross jet float valve and stop your carburetor from leaking".
The ball in the gross jet valve is only a few thousnads above the ball cage; if not careful, the float will bottom on the cage and not apply pressure to the ball; hence, a leaking carburetor, usually over the top of the main and cap jets.

Ron