Do I really need to rejet

4 replies to this topic
  • treygreen

Posted May 05, 2007 - 11:22 AM


I am new to the sport and bought a yz450f 2006. It backfires whenever I let off the throttle. Not a horrible amount maybe four or five pops when coming down from 3/4 throttle. Is this something that is bad for the bike or performance of it. I read the rejetting section and it would seem that If I do need to do this I would go to a 45 jet. Or should I just try to turn the mix screw out some. Thanks for the help.:applause:

  • Idaho_Stas

Posted May 05, 2007 - 12:03 PM


Do a search on 'jetting' and '06' in this thread and you will find more info than you want.

If it is just popping a bit when decelerating, probably not, but if it's backfiring frequently, you are running too lean.

Most folks are running a 48 or a 45 pilot w/ fuel screw out between 2 and 3 turns. Usually cleans up excessive popping and backfiring.

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  • grayracer513

Posted May 05, 2007 - 12:03 PM


Some decel popping in a YZF is entirely normal, and if the bike runs well other wise, there's no reason to chase it, as long as it's not due to an abnormal condition like a stuck hot start, or an air leak in the exhaust.

Most '06's are happiest with a 45 pilot, though, and a main int the 160-165 range. Some guys will run them at 48/170, or richer, but in most cases, that's somewhat richer than necessary, IMO.

But every situation is different, too.

  • treygreen

Posted May 05, 2007 - 12:26 PM


Thanks alot guys I may try to turn out the mix a little but other than that I guess I won't worry about it.

  • grayracer513

Posted May 05, 2007 - 02:00 PM


If you go beyond 2 1/2 turns out, it's an indication that you need the next larger pilot.

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