I have no experience jetting wise at all. Having bought a new 04 wr450 with yamaha uk fitted road kit it will not idle and revs on hunting when i want to stop. i have found that it has been down jetted a lot so i have fitted:- Main jet no 165. Pilot jet no 48. Fuel screw 1.75 turns. also Needle standard & clip position no 4. Altitude 0-4000ft. Temperature 70-80. Now the snap of power is great, Idle revs steady, couldn't be nicer, Revs don't hunt anymore, BUT at a steady rev, especially a low or mid rev it seems to choke up and cough. If i release throttle it will idle fine & if i increase throttle i need to open it up well to clear the roughness. There is no popping. What do i do? I'm not sure whether to play with the fuel screw or adjust the needle clip position or what?