bike works awsome but backfires spits and sputters on decel it works perfect til i let off the throttle to shiftdown and when i first warm the bike up and run it with the choke on it does not backfire on deceleration. who knows what this might be?

 

replace the fuel, try high octane pump gas

 

ive done that and i also changed the plug which was alittle black but didnt look to bad

 

Sounds like you might have some crud in the carb. You might want to disassemble and clean it really well. You might also try putting some seafoam in the gas.

 

I've cleaned the carb What's seafoam

 

When I checked the plug its a little black

 

Carb cleaner. The only one that I have ever seen that actually worked.

 

richen the low speed mixture screw counterclockwise a quater of a turn on the bottom of the carb.

 

ditto on the seafoam, if it backfires when you let off its a lean condition, I would lower the E clip on the main jet needle one notch which will raise the needle and give it a little more gas, other option is going up one size on the main jet, try the needle first