New '02 WR426 Jetting After Mods

I've read many posts on jetting the WR's and they've helped a lot. I also have JD's guide which is great. It seems most of the guys are riding at higher altitudes and was wondering if anyone had suggestions for jetting around 100-1500ft? I ran it stock last week and was very lean on the idle (surged and when hot the choke made it run faster and didn't kill it). It had a very slight backfire when shutting down. The only mod I did before this first ride was the GYT-R insert. My sig has the stock settings I found when pulling the carb. We are relatively humid here in Seattle so that may offset the lower altitude a bit. Anyway, I am bumping the PJ up to 45 and raising the needle to position 5 to richen it up a bit. Now that I've pulled the air box lid, it will probably be even leaner. I don't want to change too much jetting until I put the bike back together so just want ideas. I have a 48PJ on order and a 168MJ but figure they might be too rich and I haven't hit higher throttles to check the main since I'm breaking it in still. I don't want to swap the DRR for another needle until I test it and get more miles in. Thanks. :)

I'm no jetting pro by any means, but I did the same with my 02. The jetting you mentioned is stock for that year. Since you put the GYT insert in, you still basically have a restricted exhaust. The 42/75 pilot is a very good combo. I would stick with that and "check your fuel screw".

The DRR on 4 should also work well at your elevation.

If you want some real improvement, swap the DRR for ELN or EKN on 3, and leave the jetting the same.

Morris, I also have a new 426. My mods are as yours with a Baja vortip and the james now mod. I run 100 to 800 feet all stock jetting, DRR on clip 5 fuel screw approx. 1 1/4. Throttle response is crisp and clean all the way through. Couldn't ask for anything more, it rips.


You seem like an excellent candidate to make the "leap of faith" to Taffy's sea-level jetting. Heard lots of great reviews from very satisfied customers. Just find a post by "Taffy" and mimick his jetting. My $0.02... :)


Morris,I think the move to try the 45 pilot may be ok,but don't move the needle & change the pilot at the same time.Make one change at a time,IMHO the move on the needle is much more drastic,since it affects jetting over a broader area.Do the needle & then adjust pilot as necessary.

I was thinking the same thing. I don't have the 45 jet from the dealer yet so I'm trying the needle first and will put the bike back together today. I can jet it all on the bike now that I've got the BK mod done.

tctrailrider, thanks for the input. I'm trying just the clip position 5. I'll do a search on the James Now mod. I haven't gotten to checking that out yet. Good thing there is TT forums. I'd hate to do these things the old way by just trial and error. Too much wasted time.

Post deleted by MorrisWR


You should be able to fix the bottom end with the fuel screw in the bottom of the carb. Turn it 1/4 at a time as you test it, you will know when you have it right. If you end up out more than two turns you need a leaner pilot jet, and less than one richer. The rich and lean symptoms on the bottom can be hard to tell apart. If you start the bike when cold, turn off choke right away, if it idles OK I think its rich and you should first go in on the fuel screw. Good luck.

Thanks, I've been using the choke to tell me rich/lean. It's a great trick. Along with the hot start also you can figure it out pretty quick. I was under the assumption that if you turned the screw out too far to get right you needed a richer jet though. Of course, I've been tired and my brain doesn't always work. :)

If you end up out more than two turns you need a leaner pilot jet, and less than one richer.

I think that's backwards. 2 or more, go richer. 1 or less, go leaner.

oops, its been a long day. Glad you guys are smart enough to know what I mean and not what I say.

Got it set now. Took about 5 minutes to get the fuel screw adjusted right. No hesitation left. Thanks.


Congrats, enjoy the ride. This tinkering is a progressive disease. It will be great for now but soon you will start to wonder how you can make your great running, responsive ride a little better. Have fun.

Looks like I'll be doing a lot more. I thought I had it but although the slow roll hesitation is gone, it started dying when I tried to do snap wheelies while rolling. I went out over 4 turns on the screw and still too lean. To verify it, I put the stock baffle back in, backed out my BK mod screw, and put the airbox lid back on (without snorkel). Now it runs better and I can do wheelies from a roll just by cracking the throttle. Seems to still idle a bit high then drop but just barely. So, it looks like I need those richer pilot jets that haven't come in yet. I'll try the 45 and add one mod back on at a time. Wish I could head up to the mountains with some new jets for testing. Hard to do on my 2 acres.

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