My friend has a 04 yfz and in the higher rpms it cuts out as if its not firing but we changed the spark plug and it still does it does any 1 know what could be wrong anything is appreciated thanks

 

The jetting my be out. Or it may be the stator, try running it with the light on.

 

Is he running high octane fuel in it? Low grade fuel will make it run like that.

 

Well he runs 91 gas in it and i dont know where the stator even is or if theres anything wrong with it but a lotta people have had wonders bout the jetting he bought the bike used and it has a gytr slip on with a uni filter and ive got a 05 pred all stock and i can beat him pretty e z my friends stock 450 will beat him to so he needs help