Help Demon yx bogging

[derfix133]

Hi, I bought a demon yx last month and it bogs at higher revs. It has had: new clutch, cdi+harness, piston, rings and sleeve, new timing kit, carb, stator and flywheel.
Still bogs at medium throttle, all that’s left is valve train and bottom end and it’s really bugging me
Any help would be appreciated.

 

[RM_guy]

First guess would be lean jetting. Most likely the main jet or needle. Or it could be that the power valve spring is too tight. I don’t know what the setting is for that bike but too tight will keep the valve from opening and it will feel like it’s running lean. I chased a similar bog for weeks after doing a top end job and it was the spring tension all along!