I have a backfiring problem that Sears can�t solve on my Craftsman V-twin lawn tractor that began six weeks ago, after the starter and flywheel were replaced. It also now has less power, and a rough sound. During its first five years, it didn�t backfire once (even when shut off at low throttle). Now it does it after warming up, and at shut off (whether high or low throttle). Sears has replaced the flywheel key; checked the fuel solenoid, and for water in the gas. I put in a new battery. The model is DGS 6500; Ser. 371 570 8963. Could the new flywheel be wrong? Would sure appreciate any ideas � the grass is getting out of control.