A little dissapointed

Ok, maybe you guys can tell me if I am full of it or not. I bought an 02 WR426 leftover from the local shop last year. I had read all of the posts about free mods and how the WR uses the same motor as the YZ and all that jazz. I have done most of the free mods, and I am still not happy with the throttle response. It is nowhere near as snappy as the YZ400 I had. (God help the guy I catch riding that thing) Anyway, Have I simply not got it tuned propperly yet or am I wasting time trying to get it to run like the YZ? I have done the BK mod, cut the grey wire, shortened throttle stop, modified air box, toyed with the jetting, YZ timing, and still can't get the crisp throttle respose that I had with the YZ. I realize that they have different tranny's, but what I am finding is that there is a very slight hesitation when I hammer the throttle. Anyone have any ideas? Thanks,


Sounds like a jetting issue to me, if there is hesitancy. My 450 is real smooth on to the gas, but has a little stutter or so on cruise, caused by the TPS I believe.

Have you changed the needle or just the main jet?

My WR's got considerably snappier when I went to the YZ jetting in addition to the timing mods. It's been a few years since I did it and I don't remember the exact combo. I think it was EJQ and a 168. There were some real good jetting threads back then. I wonder if the new TT keeps those older threads in the search memory.

See Ya,


The JD jetting kit sold here on TT should do it. The WR are pretty lean from the factory and until I re jetted I had the same off idle stumble you are describing. It starts much better also :cry:

It is all jetting! Search for the BK mod and jetting should get rid of your hesitation. :cry:

I've done the BK mod, however I am not certain that it is set correctly. When I installed it I originaly set it without a stopwatch. Then after installing the carb back onto the bike I adjusted it for what I judged to be best throttle response. To tell you the truth, I didn't notice much difference from stock. This is the first carb work I have ever done so I am very much still in the learning phase. I should probably reset the BK mod to .3 seconds or so and then leave it alone while I try to fine tune the jetting. If you have any more suggestions please let me know. I have not changed the needle, but I have played a little with the needle position. Thanks,


I really wouldn't worry much about the stopwatch, just try to time it to where you get a slight shot right under the slide on its way up.

I think you'll notice a difference with a YZ needle.

If I remember correctly another popular combo was an EMM with a 160 or 162, going for the slimmer needle allowed them to lean the jetting with good results.

I'll search for some of those threads and post links if I find them. They were in late 01 and up into 02.

I know a lot of guys here have got great results with the JD jetting.

See Ya,


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