I have a SRV 540, I can't figure out my problem. It could be the plugs but they aren't fouled. It continuosly backfires and 'pops' when running and I can't really move with it, maybe I could of blown a piston ring, not sure. It was running fine and all of sudden it started slowing down and bogging, i made it home doing about 5mph. By the way, I pre-mix it. Any ideas on what might be wrong?