2007 yz250f jetting recommendations

I have a 2007 yz250f. I have modified the bike slightly and i am curious if i need to rejet the carb to get the best performance?????

so far i have done--

power now insert

quick shot acc. pump cover

big gun evo x slip on exaust ( even though i am running the stock header big gun still recommends re jetting the carb?)

removed the backfire screen in the airbox

i am new to the 4 stroke world.... any advice would be much Appreciated.



Hi, welcome to TT.

Probably yes. The simplest thing to do might be to get a JD jetting kit for your bike and go from there. Get an aftermarket fuelscrew if it's in the budget. I use the GYTR one, but it's a few $ more than non-oem.

Here's a link for setting your pilot circuit. The main and needle are quite a bit easier. The accelerator pump circuit can be a drag.


MJ: ride the bike at WOT. Go larger on the MJ until the bike stutters. Use 1 size smaller MJ than that.

Needle: Select the clip that provides the best control and power between 1/4 and 3/4 throttle.

AP: Tune out any off-idle bog (when riding the bike) by o-ringing your accelerator pump linkage and installing an appropriately sized leak jet.

There are plenty of posts on these subjects. A little searching should be helpful.

Hey what do you mean by o ringing the accelerator pump linkage?

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