Mine ran great unitl I changed the pipe. I got a fmf q pipe, baffle out with the lid off and pre filters in the box. I tried a dyno jet kit, but had not luck. I went to kehin jets and am at a 170 main and a 48 pilot. I have the yz450 ncvq needle at #4 and am 1.5 out on the fuel screw. It runs like a scaled dog, but does cut out at high rpms. I think it's the rev limiter kicking in. I don't see how the stator could have gone bad in the time I went form stock to the mods. It ran great at stock. Maybe there's somethikng I'm missing.

I would say you need to play with your jetting. type daggog jetting into your search engine....thatpage should help.