You need aftermarket needles with the open airbox. Unfortunately the only way to get them is with the Dynojet kit...
Make sure you have the reverse and parking brake switch issues resolved (read the Most common 660 problems sticky) because they can cause problems just above idle (but you can't break through them to higher RPMs - if you CAN, they are not likely the issue).
Remember, the pilot jets and fuel screws control mixture at closed to 1/4 throttle, the needles between 1/4 and 3/4 and the mains from 3/4 to full throttle. AN easy way to tell if you are rich or lean at one of those three areas is to close the fuel petcock and then ride with the throttle in the one position you want to test. As the fuel level drops in the float bowls, all three stages get leaner SO if your issue briefly gets better you were too rich... if it gets worse your are too lean.
Oh, and WELCOME to the forum!
'01 660 Raptor, Burgard +2+1 arms, YFZ Shocks, LSR anti-vibe, CTR pipe, jetted, K&N
'01 Polaris Scrambler 400, K&N
'02 Honda 400ex, Big Gun pipe, jetted, K&N, Lonestar +2 A-arms, Lonestar anti-vibe
'04 Suzuki LTZ400
'16 RZR XP4 1000 Turbo
Last edited by QuadManiac; 08-16-2019 at 05:16 PM.