2008 YZ450 Warm weather jetting

6 replies to this topic
  • MX926

Posted April 24, 2008 - 07:25 AM


Has anyone had any trouble with stock jetting on the 08 in 70 degree plus temperatures? My 08 runs great below 70 degrees, with stock settings
-160 main
-45 pilot
-stock needle clip in #3 pos.
-fuel screw 1-3/4
-leak jet 55

However its starting to get warm and I'm noticing the bike is getting sluggish off the bottom, with some hesitation. I adjusted the fuel screw and that didn't seem to help much, then I raised the clip on the needle, also, not much help. I'm thing about dropping the pilot jet? any advice?

My 06 ran great with:
-165 main
-45 pilot
-honda needle #2 pos.
-fuel screw 1-3/4
-leak jet #55

  • WGP

Posted April 24, 2008 - 11:02 AM


Whats your elevation/Temp/humidity??

  • MX926

Posted April 24, 2008 - 12:27 PM


Not sure on elevation, I'm in southern minnesota, i'm guessing 200 to 300 ft? Temperature is 65 and above that I'm concerned with. humidity is 50%.

I ended up dropping my leak jet from #55 to #50, and that seems to have solved my problem. I now have the snappy response I had when temperatures were near the 50 degree mark. I elected not to change the pilot since the leak jet controls mainly "off idle" response. I'm not sure why my jetting is different as compared to 06-07 jetting, but seems to be running good now.

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  • WGP

Posted April 24, 2008 - 12:42 PM


I have had good luck with a #40 Leak Jet in my 06.

And I would try a 165 main.... It is also the easiest to change with only removing the float bowl plug.

  • MX926

Posted April 24, 2008 - 12:54 PM


Yeah thats no kidding. Trying to yank that carb off and on is no fun. I'm racing this weekend, so we'll see how this setup works. thanks for the info

  • todds924

Posted April 24, 2008 - 06:43 PM


I have had good luck with a #40 Leak Jet in my 06.

And I would try a 165 main.... It is also the easiest to change with only removing the float bowl plug.

165 main is way to fat for a stock 08.

  • wolfie12

Posted April 24, 2008 - 07:53 PM


Interesting. What makes you say that? The only reason I'm asking, is because it seems like most like the 165s in the earlier model years. I think my stock 08 runs as good as its gonna with the stock pipe and jetting. But I also am wondering whether I need to rejet for the Two Bros pipe I have. It was a huge improvement, again with stock jetting.

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