04 yz 450f with Leo Vince slip on backfires. Starts first kick and runs strong!

2 replies to this topic
  • big53lee

Posted May 31, 2011 - 10:15 PM


what do i have to do to my carb? i need jetting for 9000-11000 ft. I ride the rocky mountains! any tips?

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  • miweber929

Posted June 01, 2011 - 02:57 AM


My biggest tip is to read the Stickys about jetting for all the answers to your questions, or get a JD kit.


  • grayracer513

Posted June 01, 2011 - 09:20 AM


More backfire questions? Jeez...


Look in the jetting sticky in this forum, find something close to yours, then correct for the altitude:

If you are 5000 feet higher, multiply the jet size by .95 and use the nearest available size as a starting point. At that altitude, it might become necessary to use a needle with a step or two larger upper diameter.


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