01 WR 426 Mods??


I've seen alot of posts for the WR 450, and I'm sure that the posts about the mods for the 426 are old news, but I was trying to figure out what mods specifically apply to the 01 WR 426. I'm new to this list and this bike and I'm having trouble making my way around both. I imagine the exhaust insert and airbox lid mods are standard, but does the throttle stop and grey wire mod apply to the 01 as well? All posts seem to address the 450 only. (If so, 01 YZ throttle stop or just cut it?)I know to advance the timing too, but if I do all these "free" mods will I have to adjust stock jetting or re-jet altogether, or no adjustments at all? Right now the jetting is bone stock, with the stock adjustments, the timing is advanced to YZ, and the insert is out. A local New Hampshire dealer told me to leave the lid on the box otherwise I'll be blowing through air filters after EVERY ride? (I've recently had some experiences causing me to lose faith in dealers for WR repairs, and NH guru's I should know about?) Any suggestions to walking the beast would be helpful (such as carb settings for the free mods in NH at +/- 220'..and I have a mid throttle surging when running at a constant RPM) My buddy bought a DR and I want him toasted! :thumbsup: Also, what is a Zip-ty, and is the BK mod really necessary? Where do I find help on the BK? Add a GYT-R insert or leave it out? Thanks for taking the time to read and answer all this!! :lol::awww: To make it short, what are the much needed free mods, and what are the jet settings I should be trying? THANKS!!


although written for the 250F, the 250F FAQ covers just about everything you asked about and 99% of it applies to your 426F as well. check it out and scroll down to the FREE MODS section, link is in my sig...

jim aka the wrooster

'01 wr250f

Do a search on free mods that should keep you busy for a while! :thumbsup:

Great help guys! Sometimes is hard finding what others may have named the same problem. Looks like I have to get to work. :thumbsup:

For some jetting suggestions you can start with the JD needles and probably run the jetting close to mine. The elevation of Michigan is around 700ft so its not to far off of where you are. The surging is pretty normal at around 1/3 throttle and if I remember right it was something to do with the CDI and not really an ussue on the trail since you are rarely holding the throttle constant anyway. All of the mods you listed apply to the 01. The BK mod is very helpful in cleaning up throttle response and the off idle bog, just make sure its timed correctly. Can't say anything about the Powernow but it is supposed to help the low RPM response. I've done the following mods to my 01: YZ throttle stop, grey wire, light blue wire, airbox, exhaust insert, JD jetting kit, BK mod, and the fuel adjust screw from Kouba.

where can you pick up the JD kit? Also, with the airbox uncapped, how often do you clean the filter (I know it depends on the season and dirt you get into, but whats a good rule of thumb)

JD kit can be purchased through the TT store. As for the air filter, just clean it when it is dirty. Not a bad idea to clean it after every long ride, My philosophy is that it doesn't take that long to clean it. Clean it often and you will not have to worry about it. Hope this helps,


I clean the air filter frequently since its easy and doesn't take long. Since switching to the No Toil stuff its even easier as it cleans up great. I wind up cleaning it when it looks dirty or after long rides just so its clean for the next ride.

I recently purchased a K & N filter for my 01 WR426. Has anyone experienced any problems with them? I live in middle GA, so there is little to no dust. Does anyone else ride in the southeast?


I just picked up an '02 WR426 with 150 miles on it. Basically a new, stock bike. Anybody from CO on this forum? How's your jetting? I'm going to upgrade the pipe (FMF) and open up the air box & run a Uni filter. I'll need to richen the mixture and was wondering what jets are best for altitude (5280 feet).

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