What is the stock main jet size for a 2000 CBR 600. This bike came from california. Also, What size jet do you reccomend I use for a stock f4 with a jardine slip-on and k&n filter??

Bike currently has 128 mains in all 4 carbs and sputters in low to midrange (2K-5K).

Also, what do you reccomend the air screw setting to be? Thanks!

 

You have to buy a jet kit, and experiment, but to start with that set up, use a 140 outer 142 inner start on clip #4 and start with your fuel screws 2 1/4 that should get you close, from there the fuel screws will for the most part control lower rpm and 4grand rpm cruise, needle adjustment 5-8rpm after that its all jets, but bigger is not always better