'04 YZ450 jetting

[YZ165]

I ride and race at 5000ft.+. Does anyone have any jetting suggestions for that altitude? The bike is all stock except for a White Bros. filter. With stock jetting the plug is very black, but dosen't foul. I did drop the main one and the results are the same, except for some slight poping in the midrange. I moved the needle up two clip positions after that, but have not ridden it to see if that helped. I think the pilot is rich, but any suggestions would be greatly appreciated. Oh, the air screw is at the stock setting, 2 turns out. It does hesitate if you whack the throttle hard from idle. Thanks. :|

 

[biglou]

My suggestion for baseline to start from would be 40 pilot (42 is stock), back to middle (4th) position on the needle, and leave your main down one size. I'd also go to 1-1/4 out on the pilot screw. See how that performs and tweak from there using the pilot screw and, if necessary, the needle clip/pilot size. Other than that, a JD jetting kit (available through the ThumperTalk.com store) should take care of any inconsistancies when transitioning through the cab curcuits. Essentially, what you are buying is two custom tapered needles and the knowledge of how to use them correctly. Worth the money, IMO.

 

[YZ165]

Thanks Lou, I'll give that a try. :thumb:

 

[biglou]

FYI-If you're interested, Jaybird is selling one of those jetting kits in the For Sale forum for $50 I think. That saves about $15-20 over new.