JD jet kit

Not being able to say the difference with the JD kit in the new bikes you must look at the research JD has done in developing these kits. All the WR's have benefitted from these over the years. I remember when these were begun and all the work on this site from him finding the right balance. The difference in the older bikes was phenominal and well worth the money in only the time it saved a person. Go ahead and buy the various jets from the dealer and spend the time making changes, evaluating, and changing again to find what is right for you. Meanwhile people who buy the kit will be enjoying their bike. I tried the other route for about 9 months and then bought the kit for my 99 and it solved all the little headaches for me. I appreciated all the work he did for the owners of these bikes at the time and would buy from him again in a heartbeat just for peace of mind. OK, off my soapbox.

Right on Jekel!

I'd pay twice the price to not have to tear into the carb area again. What a PITA! I can't wait for my first valve adjust; just as my bloody knuckles have healed.

JD, you're fantastic! Keep up the good work.


doing the jet ,, what causes the power increase ,, the main jet or the needle,, the rear tire just spins ,, how can I bring it back to stock with out making it leaner.

so would a jd kit work very well on a 03 model wr 450 because its an older bike that can benefit from it more than the newer bikes?

Search some of the old posts to see results on the older bikes. I know it did wonders to my 99 after I tried the I'll do it myself approach and tore in to the carb many times. Once the JD kit was in, only took the carb off to clean.

Go to JD's website, and look at the pix of all the various bikes on the dyno. That kind of research costs money, and the research is ongoing; there's an

'07 WR on that dyno.

Furthermore, JD offers us tangible, proven results, not some seat of the pants opinion (which, quite frankly is what 97% of the opinions expressed on this forum are). JD offers the jets in the kit that offer the best chance for proper tuning. If you can't get good results with the kit, maybe it's not a jetting issue (AP timing, pilot circuit problems, over oiling air-filters, bad fuel, etc.).

doing the jet ,, what causes the power increase ,, the main jet or the needle,, the rear tire just spins ,, how can I bring it back to stock with out making it leaner.

stick a potato in the end of the pipe.

The value in research is difficult to quantify, I know. We try to be as thorough as possible and look at the same questions you want answered before establishing the jet kit needles, pilot jet, main jets, and other settings. Only you can decide the value in research when it comes to tuning your jetting.

A few of the aspects that go into the WR's JD jet kits are shown below.



Dynamometer runs-


Street tire mounted for consistency-


Throttle stop changes-


Throttle marked for tuning each 1/8 throttle range-


Air/Fuel Monitoring for each throttle position over wide rpm ranges-


Gray ignition wire mods-


Steady ¼ ½ ¾ and Full throttle comparisons – Grey Wire vs No Grey Wire



Pump modifications-


Leak jet and Diaphragm effects-


Airbox Mods-




Cool JD.......you rock!

I can't believe we got the famous james dean to post.

how cool is that?

James, what exhaust modifications (if any) were made during your research? I bought one of your kits and am contemplating doing the other free mods but leaving the silencer stock. It's a sure way to stay under a 94 dB limit.



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