ds650 running choppy

[Mountainmanmyke]

hey guys i just bought a hmf jet kit with a slip on exhaust with very small restriction and have a k and n air filter with a big gun cdi box. I installed the largest jet that came with the jet kit. I took it out to camp and it sputters mid range and top end. The plugs are black. Should I go a jet smaller? or should I just adjust the air fuel screw and to what? also I was thinking could it be a faulty big gun cdi box? i am not sure, where do i start guys thanks

[brian 68]

go smaller , maybe two sizes then try it. once it runs good and pulls to redline.
find a long straight , run it wide open, then let off pull the clutch in ,hit the kill switch, drift to stop, check the plug. light brown is what you want. then at idle turn the air screw in till it affects the idle, count the turns, then back the other way until it drops the idle. set the screw in the middle, run it , then try turning it 1/4 turn each way,when it runs better try smaller adjustments until it runs best.