my yfz 450 has been sick for a long time. when i push the throttle in and go it dose alright in first gear but when i go through all the other gears it starts to stutter when it gets high rpms and eventialy quits and then it starts right back up no problem Ive jetted it all the from 140 to 185 and it still does the same thing and quits it also has an stage 2 dyno jet kit performance exhaust and K&N.

 

I would check the ignition.

 

It could possibly be timing. It might have jumped time causing it to miss at higher rpms. Also check all of your wiring to see if maybe a wire to the rev box might be messed up.

 

Ive tried thos things but it still dosent work right

 

If it were my ride, I would check the fuel filter and the tank vent.