WR450 Jetting

I have a race this Sunday but my bike is too lean right now.

I have a 2003 WR450 with stock Titanium header. Purchased a FMF Titanium 4 AMA muffler and spark arrester end cap.

Bike is too lean from 1/4 throttle to 3/4 throttle. Crackles and pops quite profusely.

Stock Jetting is:

150 Main Jet

45 Pilot Jet

DUT 5TJ-14916-DT Jet Needle

#4 Jet Needle Clip Position

Have changed to these settings eliminating leanness under 1/4 throttle and over 3/4 throttle.

168 Main Jet

50 Pilot Jet

Stock Jet Needle

#7 (raised max) Jet Needle Clip Position

If you have any suggestions or know anyone who has worked on a WR450 please give me your feedback

Here is what is working for me.



1-1/2 turns air jet

#5 on stock needle

I also had to adjust the idle screw from stock position because it was too lean at idle, I turned it out about 1/2 turn. I live at 1500ft and ride at 1500-4000ft.

if you havent done the grey wire mod and throttle stop mod you will most definitely want to do those too.


You need to try a YZ needle Part # 5TA-14916-JN-00 and start rich in the 5th clip position and go from there.

It makes a world of difference with the unchoked exhaust pipe.

I did take out the baffle and fixed the throttle stop. Are you using and aftermarket pipe? I have a FMF Titanium 4 which breaths a lot more than the stock.

In my post, you will see that most of my settings are richer than your suggestions. My elevation is higher, 4,500, but that should make me run even more rich! FMF is looking for an answer for me... but I may not get a response before Sunday.

Thank you for your help

I ride mine uncorked or with the baha insert depending on the noise rules. You have to rejet richer when uncorked.

I think it would be close to your race pipe. 170 main and 6 or 7th clip on the YZ needle may be a good starting point. I run 165 with the 5th position with my baffle in.

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