I just picked up an 06 400 4x4 and I can't figure out what is wrong with it. From about 1/4 throttle to half throttle it sputters and has close to no power, but anything above half it runs like a raped ape. I have already changed out the plug (old plug was black), and I have taken the carb apart to inspect/clean jets, needles, float, etc. I have also adjusted the air screw to 1 1/8 out like factory suggests. I am beginning to think its just a turd, does anybody have any ideas?!?