fuel screw 99 yz400f

1 reply to this topic
  • TH moto

Posted October 02, 2006 - 06:54 AM


just installed jd jetting kit and zip ty racing FMS02 fuel screw. made sure this was the right screw as apparantly the 98-99 used the "first edition" keihin carb, and this uses a different screw than the 2000 and newer bikes.

jet kit went in no problem, followed jd's advice with blue clip set on 4th setting and 170 main jet.

problem is with the fuel screw. screwed all the way in, and backed out to 3 turns out to get crisp throttle response (bike seems to run really good with jd kit) but the fuel screw seems so loose it will just vibrate out. not only turns really easy but also has a little side to side wobble. this slack is there from 1/4 turn out on.

Anyone experience this same deal, and anybody have a suggestion for a better fuel screw for the 99 yz?

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  • grayracer513

Posted October 02, 2006 - 08:37 AM


Stretch the spring on the fuel screw a little, and go up one step on the pilot jet. You should not need to back the screw out that far.

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