I posted this smae post on the honda forum with little luck. I got the K&N filter for my quad the other day and tried a suggeted #130 main jet, it ran like crap, also the jet was from a warrior jet kit, it was the round type with a notch for a flat blade screw driver, not the factory hew type, any who I put it back to the stock #122 and just raised the needle up on pos., runs great except when I am climbing hills or jam the throttle comming out of turns, I was told that I need to put the needle back to the stock pos. and go with a #125 main, the rest of the bike is stock except for a 14 tooth frt. sprocket, any suggestion or experience would be helpful.

 

The first thing that I see wrong is the main jets you're using! The small round ones are for a Mikuni carb, you need the long hex type. The needle should stay in the stock position.Do you have a stock or aftermarket pipe? If aftermarket: should try around a 128 or 130 main. If stock: try from the stock122 to a 125. Hope this helps you out.

 

With just the K&N filter, you shouldn't have to do any jetting changes.

If you've also added a pipe, you will want to at least try a (correct) jet one size larger than stock - just purchase one from your Honda dealer.

Don't freak out if you end up going back to stock jetting. The 300EX carb is big and jetted rich from the factory, so in most cases, stock jetting will be correct (but you have to check, just to be sure you're not running too lean!).

The needle is obviously too rich in the 2nd clip position, so you know you can move it back up to the center.

Aftermarket companies want to make sure you don't do any damage by running too lean, so they'll always recommend trying a larger jet just to be safe!

 

first of all, are you running a outerwear on the k&n? if so, keep stock jetting with stock pipe, k&n with stock pipe and no outerwear: go up 1 or 2 sizes from stock, k*n with aftermarket pipe, g up 3-5 sizes, to check jetting, run wide open with load on the moter, and shut it down without letting off throttle, look at the plug it should be a chocolate brown, white means too lean, black means too rich.