James Dean Jetting Kit Now Available For WR400/426/450

42 replies to this topic
  • kevs_wr426

Posted April 23, 2004 - 05:59 PM


Guys & Gals,
If you are deliberating on buying this kit, all I can say is DO IT. I've had an 02 WR426 for about a year now and hadn't touched jetting or engine (scared of stuffing it up completely:) and I thaught it was fine, UNTIL... I ordered kit. Kit arrived in a week (Australia) and followed the easy to understand instructions to the letter and fitted in an hour. Rode the bike today 22 Deg C. I couldn't believe I was riding the same bike. My bike has turned into a 450, its super smooth, yet so responsive, it's hard to explain how good the bike felt. Even the exhaust note has changed into a raspy sound like a 2 stroke without huge powerband. All I can say is I hope James reads this cause he has one very satisfied customer.
Thank you James you have obviously spent hours and hours on wr's to get us a bolt in kit that is just fantastic from the word go.
Very Happy
Kev :)

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  • jrutherf

Posted April 25, 2004 - 06:12 AM


The purpose of this note is to share my JD jet kit/ Power Now experience. I live in Michigan, and have trail ridden my 2004 WR450 twice with JD jet kit components, and a Power Now carb. insert. I have done all the modifications to get a WR450 to run correctly (GYT-R insert, cut gray wire, YZ throttle stop, and air box mods). The temperature was 60 - 70 for both rides. The first ride was with the "Blue" needle (clip in #3), 168 main jet, 45 pilot jet, and 2 turns on the air screw. The second ride was with the "Red" needle (clip in #4), 170 main jet, 45 pilot jet, and 2 turns on the air screw.
Observations from the first ride: Some pre ignition during full throttle. Sputtering during 30-50 MPH cruise. Throttle response like a two stroke. Fuel economy was 25 MPG.
Observations from the second ride: No pre ignition during full throttle. Full throttle power seemed higher than on the first ride. No sputtering during 30-50 MPH cruise. Throttle response like a two stroke. Fuel economy was 32 MPG.
PS- I wish all companies had Customer Support like James Dean. James promptly solved my concerns via e-mails and phone calls. I love my WR450. The sound of a 13,000 RPM thumper is a wonderful thing! I am curious about one thing. If KTM can sell the 450EXC ready to race, why can't Yamaha sell the WR450 ready to race? Cutting the gray wire was a little scary.

  • 42A

Posted December 23, 2011 - 07:57 PM


I have a 07 WR450F with our kit in it and not many miles on it. i have gone from a red neddle #4 to #5 clip position 165 to a 170 main, #45 pilot to a #48 and still have some decel poping. it seem to be getting better, but i'm conderned that i might be going in the wrong direction.
i've done all of free mod's,air box, pluged AIS, GYTR slip on, K&N air filter,gray wire. I'd like to start with sea level spec's and adjust from there. what do you recomend? Thanks 42A


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