I just bought it. Idles nice, but if you hit the gas hard it dies. You can drive it and get it right up to 6th gear, and run about half throttle
It will run wide open but kinda surges as you are holding it wide open. Its not really back firing though

Carb was cleaned and rebuilt (according to the seller) There is evidence of this

None the less it runs and drives and works fine as long as you never hit the throttle wide open. Any ideas i know this is a popular bike so hoping i can get some good insight

 

Does it have an aftermarket exhaust or air filter? is the air fileter box lid off? if any of these mods are done it probably needs to be re jetted and even if they arent it still may need larger jets.

 

It sounds like your pilot jet is stopped up.

 

The parking brake sensor was possibly engageged

 

Sorry I just re-read your post and it sounds more like your MAIN jet has trash in it or there is a problem with the main, not the pilot. The engine runs idle - 1/2 throttle on the pilot jet and 1/2 - wide open throttle on the main jet. So if it runs fine idle - 1/2 throttle your pilot is OK. But if it sputters 1/2 - wide open there is a problem with the main. Could be clogged which would cause a lean condition.