need advice on jetting

[northy]

My quad smokes at about 3/4 throttle. So i figured i would check the plug to see what the problem was= it was black so i new my 300ex was rich. I checked the main jet and it was 125(stock is 122 i think) - wich i thought wasn't overly high for the mods i have- uni filter & supertrapp ids2 full pipe. (Some people with the same mods on this site are running (128-135) My question is, what would cause my quad to run rich? Is it something other than the main jet? All help would be greatly appreciated

[Old Head]

I suppose there could be something else wrong but do the other people with those mods run with the air box lid removed? that will lean you out a little.

[wilkin250r]

3/4 throttle is still largely affected by the needle. Moving the clip down (raises the needle up) will lean out your mixture.