Phoenix , AZ Jetting

I have a 02 YZ426F. I would like how other riders are jetting these bikes in Phoenix. I cant seem to get it as cleanly jetted as I know it can be. I ride at Speedworld, Canyon or MotoGrande.

I ride an '00 426 at the same tracks.

Bike has a WB tapered header and ProMeg ran open (no discs) and 8oz flywheel. I also use Twin Air or Uni Filters.

Was running:

45 pilot (42 is stock)

1 1/4 turns out on fuel screw

needle in 4th groove (stock)

162 main

Did BK mod and am running:

same pilot and screw setting

needle in 5th groove

165 main

It runs very clean and crisp but I think I can go back to 4th on the needle or to 162 main.

I'll be at Speedworld this Sunday if you want to meet up?

What is the "BK mod"?

My bike is stock, running a 165 main, stock pilot and air screw and needle position.

I have played with the needle clip position alot. I am also experencing popping when I let off of the throttle.

It is adding an accelerator pump limiting screw to the carb. The pump stream stock is about 3-4 seconds long, this cuts it to .3 to .5 seconds. Makes the bike run alot cleaner. It was first posted on here by BK, Brian Kinney, Tim Ferry's mechanic. If you search topics on BK mod you will find a ton of posts. Motoman393 has some pictures and instructions on his site.

Try a 162 main.

The popping is lean on the fuel screw/pilot. turn the screw out 1/4 turn at a time till it quits popping, no more than 2 1/2 turns total out or you need a bigger pilot.

Thanks for your help, I ride on Saturday so I can be at home on Sunday.

F-pilot, were you at the races this past weekend? If so, what # and class. I ran the 30+ Nov on a KTM 520 #37. If you see me out there stop by and say hi.

No problem, glad to help.

I like to ride on Sat. too but will probably have to work this one.


no, I have postponed my return to racing until Feb. 9-10 at Speedworld. I race with the AZOTMX and usually race a second class with AMX. Either 40+ Amt or 30+ Nov.

Looks like we might be racing each other soon.

How did you do?

I'll be riding a 426 with YOT grafix and probably #18, my earned # with AZOTMX.

Cool, I got 2nd on Sat, 10th on Sunday - I got arm pump real bad on Sunday for some reason. The track was real rough Sunday, had a good start, but faded bad. Oh well, it was fun anyway. Hope to see you in Feb.

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