I have a 99 mxz 600. last year I had a piston burn down so I rebuilt the top end. it ran great for 4 miles then it started to backfire and shut down. it didn`t burn the piston again so I just put it away for the year. this year I rebuilt the motor from the crank up. thought I might have bad seals. ran great for 3 miles then it started to backfire and shut down again. I put a new coil on it also has a new stator. carbs have been cleaned. The only thing I can think it could be is a bad cyclinder or a bad electric module. has anybody have any ideas out there. hate to keep spending money on parts I don`t need!!!!!!!