Yoshimura tec insert for 03 450?

4 replies to this topic
  • highmark00700

Posted June 25, 2008 - 08:04 PM


I installed the tec insert to my 03 yz 450f and lost all bottom end. My jetting was perfect before insert was installed, and now i cant seem to get it runing right. I have adjusted the low speed fuel screw. Once you get it wound up it will run ok but I just cant seem to get it to run right.The only reason for install is to be USFS compliant! Has any one ever ran one of these?

  • VB_Racing

Posted June 27, 2008 - 01:56 PM


I have a TEC insert on my Yosh equipped 03 WR 450, and have not noticed much if any difference with the insert in or out, other than alot more noise. I did jet to the insert however. The WR powercurve is a bit different than the YZ, so I may not be comparing apples to apples. You may have to play with the jetting a bit to compensate for the restriction, or it may just be the nature of the beast. :thumbsup:


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  • highmark00700

Posted June 28, 2008 - 12:20 PM


What circut of jetting did you have to change when you installed you insert? pilot, needle, main,or fuel screw? Thanks for the input!

  • VB_Racing

Posted June 29, 2008 - 04:08 AM


On mine, I changed the main and the pilot jet.I changed to a 158 main, and a 52 pilot.( I am at about 500 ft). I also adjusted the fuel screw, but I do that several times a year anyway when the temps change here in WI. Remember, that is on a WR. The same carb as a YZ but it may require slightly different jetting.


  • highmark00700

Posted June 29, 2008 - 03:03 PM


I will try changing the main and the pilot. Thanks for the help Dave!

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