06' YZ450F cutting out!

My 450f just started cutting out real bad. Kicks over 1st or 2nd kick everytime! Idles good...but when I accelerate through mid-range and top range it starts to cut out bad. It happens through all gears. I just had the top end redone: ground valves, new seals, etc. I haven't rejetted the carb in a while so I did that. I just changed the main jet from 170 to 168. Maybe a bad thing? I know standard is 165 but my bike is piped so I heard your supposed to go up. And my pilot screw is a 45. maybe needs to be bigger? I ride a lot at the dunes (lower altitude). Maybe its not even the carb? I don't know. Any help would be appreciated. I've ridden 2 strokes my whole life. I'll admit it...I'm a newbie to the 4 stroke world

If this happened right after the top end was rebuilt, I would take off the valve cover and double check the valve train. Double check valve clearance and cam timing. If you are 100% it is correct, then it is most likely the carb. If you have ever taken the needle out of the carb, you may want to check it for damage. They are pretty easy to bend and scratch.

Already checked valve clearance. Tearing the carb out tonite to rejet the whole thing. Needle, main, pilot, everything. Hopefully thats the prob.Thanks for the input!

play with the fuel screw a bit. You might be running it lean after you put in those new jets.

Valve clearance ok, but did you check the valve timing?

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