restricted WR426

I am looking at a 2002 WR426 and the pipe is resticted plus the carb doesnt open up all the way and who knows about the air box, My question is what do I have to do to this bike to get the most out of it??? I heard a different pipe and grind off the throttle stops, but what else like timing and the air box? Please help!!!!!

There is a TON of info about all of the "Free Mods" that can be done to the 426 to get better performance. Try the search feature and you will have plenty of reading material to keep you busy for a while. In short though, the first mods should be trimming the throttle stop to YZ spec, or you can just order a YZ throttle stop from your dealer, taking the baffle out of the stock exhaust, the only mod to the airbox is simply removing the top cover - 4 screws, also, you can change the timing to YZ specs if you want to experiment a little, its really not difficult and I think it makes a very noticable improvement. Do a search on the "BK mod" for your carb, I haven't done it yet and my bike runs like a bat out of HE!!...but you might want to try it. And then there is JETTING....Do a search on that and be prepared to get overwhelmed.....HINT: Get a OBELN needle (from a YZ250F) and put it on the 3rd clip....WOW!...Big Difference!! You might want to change gearing too...try a 52 tooth rear sprocket. What else? Ummm, search for the the "grey wire" mod. Seems to help. All these things will come up in a search but heres a quick link to look at.... Look at the TECH ARTICLES there...Plenty of info....Happy WRiding!!

There are tons of sources here on TT for the mods that you may want to consider. Go to

for some very good illustrations on a number of mod for this bike. I have an 02 WR426 and an just beginning to modify and found this page to very helpful in how to do it. Yes, this is for the WR250F but they are the essentially the same. This is a beast of a bike.

1. Throw away air box lid

2. pull baffle in exhaust, I run a vortip 30 bucks lots more power and very quiet

3. Throttle stop

Then when all that is done.....

4. Jet Jet Jet

oh and

5. Buy new bars now. the stock ones bend if you use harsh language around them.

Racemile :):D

I guess I am going to replace my procircuit t4 pipe with the stock one to meet the calif sound laws. =96db But what part of the baffle did you remove to get more power out of the stock restrictive muffler to get maore power and where did you buy the vortip?? Thanks from Jim in california...

I bought my 426 today :D I am going to chuck the air box lid and pull the grey wire and pull the baffle for starters,the jetting :) can you put in a stock YZ426 jet will this work ok?? and what is a vortip??

Vortip = Similar in overall style to the stock baffle but has three different length pipes when compared to the stock baffle, which has only one. I think its gaurenteed to 96 decibals, and is a simple exhaust insert that replaces the stock baffle.

This item can be purchased from BAJA DESIGNS or white bros exhaust.

I have nothing but good things to say about this product. It also keeps the stock spark arrestor in place for off road applications.


I just wanted to say that F6Dood had a great link with that Garlic thing!!!!! I printed out about 16 pages of stuff that I can mostly do myself :) That link is for 250's but most of the mods work on 426's also.Just wanted to say Thanks for the help!!! Cant wait for nice weather to ride this baby :D

well if none of this has been done yet and the bike is a good price then youve got one hell of a good deal. This means the bike was not ridden hard or hardly at all. Buy it and just pull out the baffle. then do the above mentioned stuff. You will love it. Later


Thanks Chris, This bike was a carry over from a dealer that went belly up and my dealer bought all of the inventory, and I got on heck of a buy on it :) cant wait to go riding!!!

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