WR426 jetting help

I posted this to JD but until he can reply is there anything I can do or what did you find that worked?

"Like everyone else before, I have the dreaded bog off idle (when the throttle is wacked.) So bad that it would kill the bike. It became more noticeable when I did the YZ cam Mod. I did the BK mod and it helped (bike doesen't die). I have read all the other posts looking for the fix. Still confused so I ordered your jetting kit. Are there any other jets (leak, etc) that I need to purchase while I'm waiting on your kit in the mail? Are there any mods I still need to do?

I ride in SoCal from sea level to 2500ft.

01WR426-YZ cam mod, Air box lid off, FMF Q pipe, BK mod set to .4 sec, Grey wire removed. Stock jetting-165MJ, 42PJ, stock needle set on 4th clip"

Also tried moving clip up and down.



Have you found any resolution? I am in the exact same boat! :cry:

I'll bite............

Did you have this problem before the YZ cam install?

I had an 01 WR426 that ran absolutly perfect with stock jetting in socal, I could've sworn that the stock main was a 168.. (maybe that's what I had) At any rate, have you played around with the air screw? A lot of times the air screw could be the culprit. I had my needle in the third position always, now that I think about it I had the stock YZ needle in the bike but I remember it not being much different than the WR needle. :cry:


I tried adjusting the air screw and moving the clip up and down. I could make the bike run worse but when jetted as close as I could get it, :cry: the bike still stumbled when the throttle was WOT from a slow speed. I ended up buying the JD jet kit, installed it per the instructions with the exception of the main jet which I went with a 168 instead of the recommended 170. I have the FMF Q installed and with the 170 main it ran rich. (elevation-400ft) The bike kinda pulsed at full throttle. But now with the blue needle, 42PJ, 168Main the bike runs great. I also turned up the idle speed per James suggestion. Couldn't be happier.


Couldn't be happier.


Well alright.... :cry:

Thanks, I'll try it.

Another thing to consider is your BK timing. The general concensus is that 0.5 sec is good. This was NOT the case with my bike. I turned the squirt up to a full 1 sec and this almost entirely eliminated the bog. I had a LEAN bog due to a short duration. My carb was not dirty or plugged. I also have an 01WR426, but original timing. Try adjusting the BK with the help of a video camera, or digital camera in movie mode and count the frames. Adjust in increments until you are conviced you have the best you can get, dont forget to write down the time and your feedback. If it doesnt help, time to try something else.

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