Check to see if there's a wire mesh strainer just inboard of the fuel inlet fitting. It's possible that's deteriorating and putting contaminants into the carb downstream of the inline filter. Some needle valve seats also have a strainer above them that can come apart.
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!