I just got a new 06 450F. Just broke it in this weekend. Noticed it is backfiring alot when letting off the gas. Was getting very hot also (suspected too lean mixture) Messed with the air fuel screw, and adjusted the needle. Still backfiring but not running hot anymore. Has anybody else expirenced this? All suggestions and info will be appreciated. Also everything is still stock on the carb. Elevation from 0' to 200'.