WR426 Popping problems?

I have a 2001 WR426 that I recently timed to the YZ specs. It seemed to run fine for a while. But recently it has started popping when trying to accelerate. If you ride it real nice and slow and not rap it up it runs fine. But when you try to go past about 1/4 throttle it starts missing. It seemed to do it worse up at about 8000 feet than around my house at 5000 feet. And sometimes it doesn't do it at all sometimes it runs fine. I am not sure at this point that it is even jetting related. I was thinking maybe it is a timing problem or something. Any advice would be greatly appreciated!


Sounds like your rich on the needle, lower it by one clip.

P.S. lower the needle not the clip.

I am interested in your results. I don't have a solution for you, but would like to see how this turns out.

Keep us posted. :)

I ride at anywhere from 6000' to 11,000' and have had a problem with my bike missing around 1/2 throttle. I've advanced the timing to the YZ specs and it ran great for awhile. The local shop has changed the jetting numerous times without any sucess in solving the problem. Any ideas on what may solve this problem?

It definetly sounds like a timing problem to me, especially since you have had no luck with different jetting settings. I have a 2001 WR426 that I have rode at 2200' (where I am currently), 6000', and in Brianhead, UT at over 10,000' and I have never had any popping problems. (I think Brianhead would probably be very close to the riding climate you are experiencing, because it's dry up there, and it's pretty dry in Colorado also isn't it?) I'm running on stock jetting with only the D.I.Y. airbox, exhaust, and throttle stop modifications. You might want to retard your timing back, and see how that works for you. That's an interesting side effect of the advanced timing, if that is what's happening.

Oops, I didn't notice that Baja was not the author of the thread until now. But maybe it is the timing. Like I said, i've never experienced the popping. I have noticed the power-loss at 3/4 - full throttle, but nothing like what you guys are describing.


Missing is a rich condition. Try dropping the needle one clip.

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