another jetting ????

5 replies to this topic
  • ktmburty22

Posted January 13, 2008 - 03:23 PM


sorry to bother you again guys,i just recently put the white bros aluminium pro on my 08 yz450,it recommends to run a 162main jet at sea level,ive run the new pipe and my bike runs awesome with the stock jetting,so usually im quite happy not to change something if its not broke,but out of curiousity i was wondering what would be the symptoms of needing a different main jet and should i replace the main jet because it is recommended,thanks heaps for any help.

  • William1

Posted January 13, 2008 - 03:45 PM


With a 4 stroke, it appears to run well over a wide A/F range. You could be running a bit lean as it is now. The pipe added a bit a power, try the rec. 162, might find a bit more power. Worth a 5 dollar bill.

  • ktmburty22

Posted January 13, 2008 - 03:59 PM


thanks william,im half mechanically minded ,but never ventured into my carby,is it something that would be easy enough for me to give it a go?cheers and beers.

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  • William1

Posted January 13, 2008 - 05:29 PM


Swapping the main is super easy. Petcock off, carefull open the drain screw on the bottom of the carb, drain. 17mm wrench on the big cover nut on the bottom of the carb. Main jet is dead center inside. Remove it, swap with the 160, Do not over tighten! Put the cover on, open the petcock and go for a rip. Took longer to type this than to swap mains!

  • grayracer513

Posted January 13, 2008 - 05:43 PM


Main jet is dead center inside.

Minor point, but the main jet is offset slightly to the rear of the access hole. This is done so as to allow access to the pilot jet through the same cover. You can see it easily enough with a small mirror.

  • ktmburty22

Posted January 13, 2008 - 05:51 PM


thanks heaps guys,sounds pretty simple ,i'll give it a go and let you know how i went,cheers.

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