Help Please????

I know that everyone has asked this question a thousand times. I have read all of the posts and cant seem to get it right. I ride in New Hampshire. I have a 2003 Wr450f. I have the gyt-r baffle. I took out the airbox snorkle and purchased the JD kit. I put in a 170 jet blue needle 4th clip, zip ty fuel screw. The bike at bottom and top of throttle worked great. In midrange throttle at constant throttle it was very jumpy and seemed almost to be misfiring. Upon recommondation I put the clip on the blue needle up to the third position. This seemed to help maybe a tiny bit or it was in my head im not sure. I know that the fuel screw has no effect on the idle at all. It still runs great at low and high throttle but runs like crap in the middle. Has anyone gotten there jetting to work just right? I hate to keep taking the carb off and checking jets and stuff because the screws on the bottom of the carb strip way too easy. Im new ot playing with carbs so I dont know about all of the other jets beside just the ones that came with the JD kit. Any advice would be much appreciated. Im getting kind of annoyed with the fact that it takes this much to make a $6400 bike to run good. I just want to be able to rip out on it and not get annoyed with the jetting. Thanks alot, Denis :)


It sounds like you have the EXACT same problem I have. I put the JD kit in last week (same jet and needle as you)and when I went to test it, it ran crappy through the middle. It was recommended that I cut the grey wire due to the fact that it changes the fuel mapping. I was told that it makes the fuel mapping much more steady and adjustable to un-hook the grey wire. Also JD himself told me that the 170mj, blue needle #4 is primarily for the WR426 and the WR450 has a little bit different carb therefore you probably need to go with 165mj, red needle middle position due to the fact that this carb likes a leaner configuration. I am changing the setup to this new one today as it's my first day off in awhile. I will definately let you know what happens. Believe ME I feel your pain....I would be lying if I said I wasn't a little disappointed when I shelled out $6399+tax and I can't get the thing to run really good yet. It didn't really run that great when I rolled it off the showroom floor. I just thought that it needed to be "broke in" ???!!!

Chuck :):D

TcTrailRider is right you are way to rich. Both Jonesy920 and I have the 450's running very fast with the 160 main and red clip#4 or 5 ( I am on 5 Jonesy is on 4 ) I get some mild sputtering on decel from the richer needle setting than Jonesy but the midrange has better snap with the needle in clip #5. You are cutting out in the midrange from being too rich with the blue needle. Try our settings and report back your results. :)


Indy 450 has spent alot of time with the JD kit on his 450. He is running 160MJ and Red 5, a little over sea level.

Just a thought. Also missing is rich, weak is lean.

Hey there Indy!

I am having the same problem with turning the fuel screw all the way in and the bike still runs pretty good. Prior to the JD kit It would stall if I turned the fuel screw in all the way in. I thought of changing the PJ to a #42 from a #45 but would have to order it cuz the 2 smallest PJ's I have are the stock 40 and 45. If I run the 40 PJ I will have to run the fuel screw out 3 or more turns and I am afraid at that setting it may fall out while riding. Over the weekend I changed the needle clip on the blue needle from #4 to #3 to lean it out. I got to ride Monday to test and found the popping or backfiring on start up was pretty constant and prior to going to #3 on the needle it only popped maybe 20% of the time. the temp has been in the 80's constantly around here but at sea level I didn't feel I needed the red needle. Maybe the blue needle #4, a 162 or 165 MJ with a #42 pj, fuel screw out 1 1/2- 2 turns will do it, I'm just not sure. THANKS for any advise!

Smoke :)

Foursmoke, Leave the pilot circuit alone. I have tried all of them from 38, 40 , 42, 45, 48 PJ and my results show that the 45 and 48 are your best choices and really do not need changing for the summer. Yes you will be rich at idle and that is why it is not dying when you turn in the screw. I find you will loose bottom end because of the overlap of the needle and pilot circuit near 1/4 throttle. The Wr450 needs the 48 pilot even though the idle is rich during the summer. You can get better idle but you will lose the bottom end grunt. As long as it idles well without stalling or surging when riding on the trails leave the 48 pilot in there. My buddy Jonesy920 is using a 45 PJ and is happy. Try the red needle in clip #5 when you get a chance.

Happy Trails! :)

Cutting the gray wire changes IGNITION mapping!! I have an 03 450, all I have done, jetting-wise, is a Zip-Ty Fuel screw(for ease of adjustablity...)changed MJ to a 162 and PJ to a 48. All free mods done and she flat-out bogging, stutters or pops or any of that crap.Most of you don't need to do all the crap you've done, just some minor tuning should get you there! I spent less than $10 on necessary parts to re-jet her....the ZTR fuel screw was for my convenience. :)

Thanks Indy, I will try the red needle #5 for this Sundays ride and let you Know next week what I think. Thanks again.

p.s. I love this suspension from Pro-Action ( re-valve fr & r, 5.6 rear sring, stock front srings and fluid viscosity modified :D)

Smoke :)

Indy what elavation and temp are you at. I just purchased the jd jetting kit and am wondering what to start off with i ride from 4000 to 6000ft. or more and the temp's around 80. i have a yz pipe on it and am currently using a 162 main and 48 pilot and it's running fine but not great. :)

Try the 160 main with red # 3 . I was riding in Colorado between 8,000 and 11,000 feet a few weeks ago with the a 155 main and the red needle and it ran fine. Start there and see how she runs. :)

All right Indy you came to Colorado and you didn't try to hook up with any of us natives. Your on the list now!!! :)

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