Incurable Mid-Range on '02 426

8 replies to this topic
  • ThumpDR

Posted February 18, 2003 - 08:23 AM


My brother and I have gone through the archives and tried every which way to get his damn '02 WR 426 to run right with no luck. Here's where we're at:

Airbox lid is off
Grey wire cut
EKP needle installed with clip on 3rd position
168 mainFuel screw 2 turns out
Pilot is 1 richer from stock

Starts fine, pops and bogs in the mid and top. We ride it at about 4,500 feet.

Need your guys help, please. We've been through the archives until our eyes bleed and there is no answer. We've tried the stock needle and 2 other different ones but this EKP seems to work the best. We're close but not good enough.

Help. Help. Take mercy on the DRZ guy who can't help the WR guy... :) :D :D

  • jwriott

Posted February 18, 2003 - 08:42 AM


I'd search the Taffy and LarryCo jetting mods.

I'm riding at a higher elevation than you but my first guess is you are way too rich. I'm running a 152 main and even at 5200 feet, it runs very good. You can see my jetting in my signature, courtesy of LarryCo.

I did the pilot fuel jet, main air jet, needle, main fuel jet and pilot air jet change.

I'd also do the BK mod. Mine squirted fuel for 3 1/2 seconds and I fouled a lot of plugs.

You also don't mention the exhaust baffle removed or installed?

  • Hick

Posted February 18, 2003 - 08:53 AM


You are way too rich for that elevation IMO.

I am at 4,000+, Here is the jetting on my friends '01 WR 426, unstopped, uncovered, uncorked:

EKQ #3
160 main
Stock MAJ (200)
40 pilot
PAJ at 85
Idle at 1.5

I'm sure a 168 main would be too rich for him.

  • ThumpDR

Posted February 18, 2003 - 09:28 AM


Sorry, he's got the White Brothers E-Series S-bend on there with 12 discs.

I'm gonna try Mr. Max's jetting specs first since he is close to our riding elevation. Guess it won't be much longer my DRZ will pull on the old WR huh? :)

Thanks. I really appreciate the advice.

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  • jwriott

Posted February 18, 2003 - 10:31 AM


I am in no way a jetting expert and I think Hick is probably more qualified to help you sort out your jetting.

I just know that my bike was incredibly rich before I did these changes and now it runs a lot better. It starts easier, no backfiring, revs quicker and the plug looks good. My old jetting was with a 160 main, and everything else stock in the carb.

I am a little higher than you and if I remember right, LarryCo had some info on riding in Moab which is about 4500 feet. That being said, my jetting may be a little lean for your altitude so I'd search for his information.

Afterwards, I'd be very surprised if you could out pull a WR426 with your DRZ.

Good luck,


  • Hick

Posted February 18, 2003 - 01:31 PM


Sorry, he's got the White Brothers E-Series S-bend on there with 12 discs.

That same jetting worked equally well on my other friends bike w/ a WB R series. Also worked on my YZ w/ stock can. Also worked on my YZ w/ a reverse megaphone TA. And on my friends' YZ w/ a Yosh slip on. And on my '00 w/ a PC T4. And on another WR w/ a PC T4.

The stock WR uncorked is as free-flowing as any aftermarket system. If you put an aftermarket pipe on a KTM or DRZ you will probably benefit from some jetting changes, but an uncorked WR or stock YZ is pretty much zero backpressure to begin with.

Just my two pennies.

  • tctrailrider

Posted February 18, 2003 - 03:40 PM


It appears that you are running pretty much the same altitude as Hick. You are lucky, my suggestion would be to take his jetting recomendations to the bank. On this side I would rate his knowledge at the top.

  • captain_S

Posted February 19, 2003 - 12:07 PM


Make sure you guys got a good plug in that motor,k is gonna give you a lot of fuel in the mid and top range,maybe try an m (with a new plug),i still got jetting probs too,but i`m thinking that there is a needle out there that has got the rite balance,of root,mid and taper,e series is where it`s at though,just gotta get the rite combo,also make sure the air filter is fresh!,a slightly dirty one can throw you well off the mark.As for mr knievel well he`s gotta be the best bar none!

  • Taffy

Posted February 20, 2003 - 02:05 PM


i used to visit the DR side when they were all trying jetting changes and the taff mod (where does BK come into this one!!) and they were running down to 135MJ at 10,000ft so pull the MJ down and down in tests and when the top end runs out of breath try lowering the needle.

the tests are simple, the results clear so get off your arse, don't bench race no more get up them thar hills and test.

1 hours work. no rad flaps, one tank bolt, one seat bolt no r/h engine mounting plate and pull that carb out the side. no probs!

oh and BTW you can even change the MJ without removing the carb.



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