Jetting Help PLS

3 replies to this topic
  • unclemd

Posted November 15, 2009 - 03:45 PM


Dealer installed Hot Cams in my 07 WR450F did the 1/2 hour break in and valve check. Installed a pro circuit header pipe with a LEXX MXE Silencer and a JD jetting kit. Called JD jetting to help with jetting for my mods. I was told to use YZ specs for the jetting installed 170 main jet, 48 pilot jet, Blue Needle on the 3rd clip(temp is below 50), installed the large O-ring. When riding the bike under light acceleration up to about 1/4 throttle it has a sputtering type of miss. This is not present when accelerating hard. Elevation is about 500'. I'm thinking that the needle position is the problem but i am no expert.

Am i running on the lean side or the rich side or is there another problem?

  • tribalbc

Posted November 15, 2009 - 04:30 PM


I would wait for spring to fine tune your jetting. If you do it now you will be too rich come spring and warmer, fairer temps.
I just did YZ cams and a HC piston on my 07 this fall. Already had A YZ exhaust. Didn't seem to make a huge difference to my previous jetting but I'm waiting for spring to fine tune.

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  • yams

Posted November 15, 2009 - 07:16 PM


i had the same issue with my '04 i used a jd jetting kit and e-mailed jd before i installed it he gave me a different spec than what is listed in instructions if i remember it was 170 main red needle on 5th clip counting from the top stock pilot and fuel screw
1 3/4 turns out what i had was an excessive stutter 1/4 to half throttle it is about 95% gone i can live with it ,i was loosing my mind with the stutter,try e-mailing james at he is very helpful good luck

Edited by yams, November 15, 2009 - 07:17 PM.

  • unclemd

Posted November 16, 2009 - 01:06 PM


Toke out the JD Blue needle on the 3rd clip and replaced it with the JD Red on the 5th clip removed most of the sputter/miss what is left i think is normal. Bike pulls hard all the way through the power curve. Temp is about 55 today and the red needle on the 5th clip seemed good so i may need to go to the red needle on the 4th clip when the temps warm up?


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