Emergency help needed.

4 replies to this topic
  • hawkins1

Posted March 19, 2004 - 08:15 AM


I just installed a fmf titanium pipe and mid pipe. I am getting a ton of back fire do I need to loosen the fuel screw on the bottom of the carb or re-jet it. 01 yz 426

  • BrandonW

Posted March 19, 2004 - 08:19 AM


Turn the fuel screw out, to a max of 2 turns. If that does not make the backfire subside, then your pilot jet needs to be changed to the next bigger size, and redeaux.


(New pipe is allowing it to breath much easier, and I bet your air/fuel ratio is a little on the lean side. Good luck!)

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  • Indy_WR450

Posted March 19, 2004 - 10:50 AM


Most likely need to raise your needle. Dont mess with your pilot until you get the needle closer. :)

  • WR450F_RDR

Posted March 19, 2004 - 01:12 PM


I second Indy's thought, raise needle first, maybe even go to a larger main jet? ( you dont list your current jetting settings?)

  • Treebark

Posted March 24, 2004 - 05:22 AM


The fuel screw will only effect idle and off idle fuel air mix and would change the main jet to a 170 or 175. I put a stock yz muffler on and had to change main to a 175 and that took care of it. The needle may need to be raised if your having a throttle response problem such as having a hessitation. My 04wr450 expierenced the same problem after I changed my exhaust and Raised it one notch to (#5).


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