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Jetting for the exhaust


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I have a 02' Yz250F and I bought a complete Pro Circuit T4 exaust kit for my bike. The bike seem to be running extremely lean. The head pipe turned bright blue in about 1 to 2 minutes of starting. I can not figure out the jetting for it. A local shop told me to move my needle from the 4th notch to the 5th notch and turn my fuel screw in 2 3/4 of a turn in. When I did that it bogg down with a quick twist to the throttle. So I tried to play with the fuel screw and could not get it. I live in north texas so if any of you could help me I would appreciate it.

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Generally when adding a more free flowing exhaust you will need to richen your jetting. Start with going one higher on the main jet. The do a plug chop test to determin if you need to go richer. You may also need to richen your needle but only do that after you have your main jet dialed in.

There is no way for anyone to tell you where to put your fuel screw. That needs to be adjusted individually on each bike. You can do this by feel: adjust until the RPMs are the fastest by slowly turning the screw in an out. Or you can use a tach. If you need to go more than 2 turns out go up one on the pilot jet. If you are less than 1 turn out go one smaller on the pilot jet.

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