backfiring need some help

[6858-400ex]

my 400 sat in the garage for probably 6 months. it ran great when i parked. it backfires when i let off the throttle. i drained the gas tank, cleaned the carb,new spark plug, just put a new battery on it today. i dont know what else it could be please give me some ideas

[mcgrath]

did you disassemble carb to clean it properly or just pull the bowl and quick clean. It sounds like a carb issue and all jets and internal parts need to be cleaned thoroughly. For future storage I usually drain fuel and run engine until uses all fuel in the carb. Never have carb problems.

[Snipe]

Backfiring when on letting of the throttle usually means jetting check the plug and tell us what you find.