A fellow 02 WR426 rider in need of help

I've had my WR426 for 4 months now and I just found this site. It talks alot about re-jetting the carb, bk mod, backfiring solutions, and yz timing. Lately while riding I too can feel the "lack of punch" my bike should be having. I live in colorado and ride from 7500'-13000'. Could someone help me on getting the right jet and needle settings for my carb for my area. Maybe what others have found to eliminate the bog that I can definately feel now. I really have to jerk the wheel to wheelie over things. It shouldnt be that way with this monster. My bike is stock right now and like many others I know I can get more, crisper power out of this beast. I notice the backfiring alot more now too ever since I read it on this forum. I, like others, want the max out of my bike. Please help!!!

Bluedragon we need to get together I live in Arvada and am fighting the same problems. I have done the BK mod and will show you how.

All this has been covered a million times, here are some more recent posts:

Re: High-altitude Jetting results - Colorado

Re: '02 WR426 Jetting in the Denver area

Re: Re-visit High Altitude Jetting

As both of you guys have noticed, altitude affects jetting. You need to jet your bike. Another thing you may NOT have noticed is that intake and exhaust changes also affect jetting. The fact is that as soon as you remove that pencil-sized exhaust restriction you need to rejet.

If you own a YZ and live near sea level odds are your bike runs okay. Otherwise you are missing out if you run stock jetting in a 426.

Search on "Free Mods" first and formost...........

If your uncorking the bike for the first time (lid, throttle stop, butt plug), I'd suggest YZ jetting (again, search function)..........

If that's not enough punch, look into YZ timing...........

Wealth of knowledge on this site, search and you'll have weeks of reading to do...........

As you can see, I'm very close, let me know if you need help.............


Dodger :D:)

Here is what I am using right now (in my signiture) and it seems to work great. Bog is barely noticeable and 3rd and 4th gear wheelees aren't a problem. The E series needles make a huge difference compared to the stock D needle. All of the Denver area riders have fairly similar jetting, so it should give you an idea. Check out the high altitude jetting results. I work in Arvada so let me know also if you need any help.

First of all, thanks guys for all the help. I am really just overwhelmed by all the diffrent settings to my carb. I really dont know too much abot re-jetting carbs but would like to re-jet it once and not worry about it every weekend. I ride woodland park(7500-9000) one weekend then rollinsville/St. Marys the following. I just would like to find a happy medium for both. Can anybody help? Also Ive heard about this BK Mod and ACV Mod. What are they and how can they help my performance? Ive tried to read up on them but its alot of reading and it really doesnt explain what they do. Help!!!!! Thanks guys

Attn. Dragon:

How to Rejet your bike.

Step 1) Go to TTalk and find jetting specs of members w/ same bike who ride at same, or close to same, altitude and climate (see links above).

Step 2) Remove carb, remove jets and replace with parts specified by best consensus of TTalk members. Consult owner's manual as needed.

Step 3) Ride and be happy.


BK Mod. Named after Brian Kinney (I think that is his name), Tim Ferry's mechanic, who originally posted this mod to TTalk. It refers to a tab cast into the body of the '00 and newer 426 carbs, through which you could drill and tap a hole to accept an adjustment screw that would limit, or act as a stop on, the accelerator pump mechanism.

ACV valve: refers to the Air Cut Valve, some kind of emissions foof found on WR carbs that leans the mixture at idle. Do a search for detailed instructions on how to disable this sometimes troublesome carb engineering band-aid.

Hope this helps.

O.K, now I have some settings I would like to try for my carb. The next question is Where do you guys shop for your needles and jets. Can you buy a jet kit with numorous amounts of jets? Do you go through Yamaha or is there a better place? I am ready to explore the world of RE-JETTING.(LOL) Thanks for the input.

You can get jets at your local motorbike store. Try Excel Yamaha, Fay Myers, or where ever down there in Denver. You don't actually need to go to a Yamaha shop, just a shop that carries jets for Kehin carbs, which should be most of them. Needles may be a little harder to come by, some need to order them (try Sudco @ sudco.com), but shops may carry some. I was able to walk into the shop up here in Bldr, and buy my YZ needle.

Don't fret too much about removing the carb, it looks complicated, but it's actually real easy to work with.

Have fun :D.....

Dodger :D:)

Thanks Dodger, I lived in Boulder for a little while myself. I was wondering where else do you like to ride that isnt too far from us. I like Rollinsville and Empire but is there any other places that you could ride in a day? P.s Cool website!


My jetting is in my sig line if you want to try that. Notice though that I have a vortip exhaust, throttle stop cut and the airbox lid is removed. If you want some actual help I would be happy to give you a hand.

I try to tune my bike a little different than most but it seems to work. I think I told Wicked how I did it on a winter riding thread but I dont know for sure.

The carb is really easy to work on. If this is the first time you have done jets, I would suggest that you only do one thing at a time, test ride it, and then change something else. This allows you to see how clip positions effect performance, and MJ vs. PJ performance. It was a real education for me.

Last advice: Set the bike up for the way you like to ride. This bike, throttle stop removed, can generate some monster hit late in the throttle. Some people love it. I dont like it for the way I ride, so mine has been tamed down a bit.

Good luck, You wont belive how much proper jetting effects the fun factor.


I ride up around Apex, Kingston Peak, James Peak, Rollins as you do. I like being up in the high country.........nothing like it.

But, for normal weekends, West Magnolia area just south of Nederaland is real sweet, some awesome single track, and a lot of real fast fire roads. We do a ride from West Mag, though Eldora, and up to Yankee Doodle Lake.......it's a trail called Jenney Creek (she likes to drown bikes :)). If you've never done the ride from Nederland to Winter Park, I highly recommend it, very cool. We also have a mostly single track ride from Bldr Canyon, though the next two canyons to the north, ending up at Jamestown. We used to be able to go all the way to Peaceful Valley, but they have since closed the Battlerat Trails :D. There is always Lefthand canyon, oh boy, that place is nuts. Real loose, lots of 4x4's and quads, but there is a lot of trails, and let me tell you, VERY GOOD PRACTICE!!!

Other than that, I REALLY try to motivate myself, and go to farther places, stuff around here is just to crowded, over used, and well the same ol same ol. I rode Rabbit Valley again this weekend, OOOOOOOohhhhhhh man, what an incredible ride.

Feel free to shout at me for riding, I'm on the scoot usually both days of the weekend.


Dodger :D :D

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