I have an 07 wolverine 450 that i bought with 19hrs on it.it backfires at high rpm when i let off on the throttle.i done a search on here and couldnt find a definate answer.too lean,too rich,bad gas,bad plug...it is bone stock besides the tires and the guy i bought it from said that it has always done it.any help would be appreciated.is it true that in order to get to the fuel/air mixture screw on the carb,i have to drill a plastic plug out?what kind of stuff is that?lol

 

you may need a valve edjustment seen many dirt bikes and for wheelers do that when reved way up and then back off because the valves need to be shimmed id say take it to a local repair shop dont take to dealer they will fill you full of crap