Even a tiny piece of debris under the needle valve will cause flooding. Is there some type of fuel filter between the fuel pump and the carburetor? If not, try installing an "in line" filter. The small clear plastic filters with nothing but a piece of screen mesh inside are virtually worthless- - - -get one with a metal housing a couple of inches in diameter.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!