Pull the carb, and do a thorough cleaning with carb spray and compressed air. Back flush all pilot/air ports: cover the pilot screw hole and the jets threaded hole with fingers and flush from the pilot inlet port so cleaner comes out the hole in the main bore, then cover the hole in the carb bore and the inlet hole and flush from the jet threaded hole so cleaner comes out the screw hole. Back and forth forcing cleaner and air out all the holes by alternately covering two holes at a time in the pilot circuit. Straight forward and the proper way to clean ports. If you can, drain the tank and use race fuel or at least the same grade and brand of premium for jetting runs. Establish a clean tank, fuel and good flow, clean fuel filter and petcock filter if it has one, floats not hanging up, etc.