my neighbors 426 has been sitting for about a year and i decided to take it off his hands. when i run the bike it backfires excessively and runs extremely hot. ive checked the valves, they are ok, changed the oil, cleaned the carburetor and jets, adjusted the idle screw, put new fuel in, checked the coolant and air filter. the one thing i havnt done is adjusted the pilot screw. i dont know the factory number of turns so i havnt touched it. could that resolve my problem and is there anything else i should look for?