2008 kxf250 cuts out when you hit the throttle fast but revs and runs great other then that. Rebuilt carbs already. New cdi box. Could it be the pilot jet?

 

Could also be on the spring/needle. There may be something slipping.

 

Mine does the exact same thing I have a klx 125L and it runs phenomenal no issues whatsoever, Except for when I rev it too quickly it wants to die on me but if I let off it continues to run, but if I hold it when it starts to die on me it does and it stalls. I'm not sure what to do here any suggestions?

 

Check your stator, make sure its not loose, make sure your pump is good, make sure your leak jet is clear and timed right. If your unsure how to do that youtube it.