[monsterbar]

My '02 Raptor is new to me and back fires as I let off on the gas. I first ran 86 octane then change to 92 octane and changed the sparke plug. It still back fires but not as bad. It has been modified, but not by me. It has a DMC pipe and it's been jetted. Any suggestions for the best way to resolve this issue of mine.

 

[maxb750]

you're runnning lean....richen both fuel/mixture screws underneath the carbs a quarter to half turn at a time..

 

[jlraska]

you're runnning lean....richen both fuel/mixture screws underneath the carbs a quarter to half turn at a time..

if this doesn't help you may possibly need to adjust the valves

 

[akawilliam]

Check valve adjustment first before makeing fuel adjustments :thumbsup: