Could be anything from float level adjustment to jetting and needles or even the fuel filter . More details required to diagnose. Could even be a lump of varnish (solidified gas residue) on the needles.

Last edited by locopony; 08/31/2014 12:20 PM.
I have no faith in human perfectability. I think that human exertion will have no appreciable effect upon humanity. Man is now only more active - not more happy - nor more wise, than he was 6000 years ago. Edgar Allan Poe