went to start it the other day and it wouldnt rev at all. It was running good, rebuilt the carbs 4 weeks ago. Now when i start it and try to give it gas it boggs and puffs air out the exhaust (idk if it would be considered backfiring cause its not a louder pop but big puffs of exhaust. Ive taken the carbs off twice now and cleaned them, checked the reeds, replaced plugs, checked that its getting fuel. The TORS is disconnected and no parking brake. motor was rebuilt recently and has compression. Pretty much stock except a boost bottle.