WR426 to YZ timing results

In preparation for a 70 mile hare scarmble this last Sunday I decided to set the cam timing to YZ specs. I don't want to exaggerate this out of proportion but it was incredible. The punch in the midrange brings it closer to the feel of a 2-stroke. This was extremely useful pulling out of tight corners in deep sand washes. As for the down side, I didn't see any in performance. The first half of the 35 mile loop was very technical with the hardest being a 400 foot assecent up a rock fill canyon. I was still able to lug it in 2nd and 3rd without any noticable loss of lowend from before to conquer these types of obsticles. I feel bad for the guys of similar riding abilities that had to deal with the point and shoot power bans of the 2-stokes. I give this mod two thumbs up and would never consider switching back!

The only down side was the bearing retainer clip. I stuffed the timing cavity with paper towels and still managed to drop it inside the engine :D. Fortunately it came right out with a telescopic magnet :).

Thanks for the report. I am considering the YZ timing but have not yet pulled the trigger. I am awaiting the arrival of a Thunder Alley pipe and want to individually evaluate the performance of each mod that I do. This scoot already has a serious grin factor. :)

Good Luck w/ yours.

I'm glad to hear that! I really want to go with the YZ specs but didn't want to lose the low end power. Did it take very long to switch over and did you have to do anything to the jetting?

I did it and loved it, but I'm use to 2 stroke MX bikes. Some guys that are not use to that kind of power or are not real aggressive like the WR timing better for its smoothness. The nice thing is if you do change it and don't like it you can change it right back.

My son-in-law and I did the YZ timing on his 2002 WR today. Took us a couple of hours but we were very cautious. To cold to take it for a spin and give a report on the power change. It certianly sounded different and seemed to rev quicker during dry revs. If you know anything about wrenching it shouldn't be any problem. Just as all the how to's state be sure and watch the bearing retainer clip. It can easily get away from you and down into the engine via the timing chain galley. My goal today was to get my throttle stop cut. Turns out I don't have one. Darn meddling dealers. Now I have to call them and see if they have it so I can give it a trim. Depending on what you read, some say it will confuse the TPS at high rpm. Better safe than sorry I guess. If nothing else a positive throttle stop sounds better than using the top of the slide for the stop.

The real danger of not having a throttle stop is cracking your slide. Do a search on that, it can cause serious damage.

Like Chaindrive said!!!

yeah, i'm with ryme.... any jetting changes REQUIRED with the yz-timing, or is teh yz-jetting an independant mod? i wanna yz-time my wr for this season, and would like to do it one step at a time, so i would like to change to yz timing, ride it a while, then swap jetting in future if still desired, so again, is yz-timing okay with current jetting, or did you need to rejet with timing?


racer36 :)

In my experience changing the cam timing does not affect the jetting. It does seem to idle a bit rougher, I may have fiddled with the idle mix and speed, but that is about it.

Also, I think going w/ YZ jetting (provided you are uncorked, unstopped, & uncovered) is every bit as much of a performance gain as the YZ timing, and should cost under twenty bucks (about all you need is the PAJ and needle).

I should add I have no experience w/ the 400 however, the above applies to the 426, I don't even know off hand the difference in YZ 400 to WR 400 jetting.

Hope this helps.

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