dont know where to go from here i am running gyt-r jet kit 170 main 45 pilot 2 turns out on mixture screw 4 clip on the needle . the is the best i have gotten yet starts good idles clean everything pretty well until top end then she starts to stumble and miss elevation is 320 ft i have changed jets around several times and at times had more power but a constant backfire on de cell this is running clean just b=need to fine tune to elimanate the top rpm stumbles oh yeah i was running with the lid on at first then i thought i would try it with it off it did cut down on the stumbling but did not elimate it any suggestions

 

i run a yoshi pipe a 172 main jet needle in #6 position and it runs awesome