Jetting Dilemma!!

I've looked on the posts about different jettings on the "WR",but I'm a little confused :) My bike is a 01 WR 426F(love it!)Couple small problems I'm sure someone has ran across..

1)Airbox lid removed

2)Throttle stop trimmed

3)YZ Timed

4)White Brothers"E" series Pipe w/ stock header and 12 disks.

5)Main Jet-#165

6)Pilot Jet-#42

7)Needle-OBDRR clip in #3 slot

8)Fuel Screw-2 turns out

Bike just RIPPS all through the power band, @ 3000', but when I get to about 5000' it runs great until I shut it down and it cools off, start it up, take off and it pops and back fires @ 1/4-3/4 thottle? The bike starts fine,(never had a problem starting)Seems to run great @ WOT .I feel it has something to do w/ the needle, but I just don't know for sure..I thought about moving the clip up a notch thinking it was running rich do to my exhaust disks turning darker@ the higher elev. rides. I just don't know?I also thought the jets were fine due to the higher elevation..I have a buddy that runs the "DTM"needle in his wr400, same kind of situation, w/ a MJ-175/pj-45..So the only thing different is the "DTM"needle..I've been reading alot on this site trying to learn more about those needles, but it gets kind of confusing..Any help would be greatly appreciated!!! I think I'm really close!...Thanks........TIM

Your jetting is very close to what should work. Moving the clip 1 step leaner is an option. You should first consider the grey wire discussions. Cutting this wire (which is for US models only) may be all that you need to do. Having removed the throttle stop and changed the exhaust make this a good choice.

The DTM is a richer needle from 0-1/4 throttle. It depends on what clip it is set at whether jetting is the problem. #3 is usually a good setting.

[This message has been edited by James Dean (edited 07-01-2001).]

I know my WR will buck sputter, stall, and be all around unrully if I dont warm it up good first. Is it possible you are letting it get too cool and trying to jump on it and go before letting it warm up again? How long of a cool off are you talking about before you are having trouble? James Dean is the Carb man! He can square you away. Hey James, what type of device do you use to adjust the fule air screw while the bike is running? I saw a trick little tool on the web but was wondering what else might work good?


Get the Kouba T-Handle. It goes onto the existing screw and allow you to tune with gloves on, anytime you want.



99 WR400f, YZ timed, MX-Tech suspension, Scotts steering damper, White Bros E-Series (12 discs), tapered header and a/f. Kouba T-handle for the fuel screw. Works Connection billet throttle tube and frame guards. Cycra Pro-Bend, triple clamp mount handguards. Thumper Racing rad guards, Renthal Jimmy Button highs, YZ Tank and IMS seat, YZ number plate, odo removed, EKP, 48PJ, 175MJ at 500-1000' Thanks James Dean!


I use a Moose multi-bit screw driver made to go in a fanny pack (4 tips in it). The smallest flat blade tip on it without the handle is short enough to fit. I can count the flats to check the turns out. Hot is difficult as it is tight to reach and gloves make it harder to turn, easy to get burned knuckles bare handed.

Thanks to all for the reply!!! I kept my stock "DRR" needle that came in the 01 wr426, put clip #3,as I've been running @ 3000'...I also moved up from #165 MJ to a #172, and the PJ-from #42 to a # 45 w/ 1.5 turns out on the fuel screw.Rode it @ 5000' and it ran great!! No popping or anything!!That's where I'm confused, I thought the higher the elevation, the leaner the jets should be? I don't know...Oh well, runs great now! I'll have to try 6000'-7000'now!!..Thanks again to all that replied!


The stock pilot jet is too lean for many setups, the fuel screw can be turned out though. At sea level a #48 pilot jet works well with the #100 pilot air jet.

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