I just bought a 2001 520 Ktm that had a 400 cylinder and piston on it. I just had the head rebuilt and ported with bigger intake valves and put a 520 cylinder and piston on it. I also had my 39mm carb bord out to 41mm. My question is I wonder were to start on my jetting. The carb had a 185 main jet with a OCEMR needle and 48 idling jet and when it was a 450 it ran great with that jetting. My problem is I have tried several different main jets and different needle positions and can't get it to run right. The best run was with a 190 Main and the needle on the first clip but it still sputters on top. It seems to be good from idle to 1/2 throttle but sputters on top. I know I need a different needle but not sure what to start with. Any help would be appreciated.