Motorcycle Repair: suzuki 650 savage motorcycle, exhaust flange, suzuki 650

Question
my bike runs great up to 45 miles per hour then it starts poppingand missing when you let off throule backfires what do you think thinks

Answer
Lonnie,Try this to start with. Put in a new spark plug but go down 1 number if its an NGK plug, for example if its a B8ES go to a B7ES. Also the carb may need gone through as a fuel crcuit may be plugged. Also check the exhaust flange at the head. Yamahas will loosen up and suck air in and back fire on deceleration on their 450's.