I uncorked my exhaust on my 01 wr426...

Do I need to re-jet and if I do, what size jet/s do I need to go to.



i rode mine all summer in chadswoth,n.j. and had no problem with it uncorked


can u pls tellme how to uncork one's exhaust?


hey as you look at the exhaust it will have 3 bolts going into the main body , don't touch those. the bolt you need is right there holding in the center piece,(spark arrestor)should be pointing to the ground. take it out and pull the plug out, then have a blast.

not sure, but don't the WRs also come with a throttle stop? may want to check that out on this site somewhere... could have sworn i read that here...but, i swear a lot.. :)


I'm not sure your exhaust is the same as US models.

More importantly, What's a DKWOK?

Can you cook in it ? :)


my wr4 exhaust does not have any bolt or screws to hold the outlet, its all welded up, maybe i have to cut open it???


This should tell you everything you need to know.


DK, you have the same exhaust system as the ROTW (rest of the World, not North America) the same as the Canadian, Australian & European models... you can't really do much, and you can't do the throttle stop mod, the grey wire mod - but you can do the airbox lid mod, the YZ timing and the spoke blueprinting & balancing mods...

If you want more from a pipe, it will have to be an aftermarket pipe or at least a header...



thanks a lot,

somebody here wanted to sell me a pipe,

its not only noisy, its expensive,

i dont need those few hp anyway,


:):D :D

Do these mods apply to the WR400F as well. I know about the airbox and the spark arrestor, but was unsure about the throttle stop and cutting the grey wire.



2000 WR400F

2002 YZF R1

Yes you can do all the free mods on the 2000 WR400F. Start with the air-box lid and the plug on the pipe. It's not the spark arrestor, it's just the small plug at the end of the pipe. Then there's the throttle stop. Cut it down 10mm or to an overall length of 24mm. The stock setting only allows for 1/2 throttle & this'll open it up. Once you've done these, ride it & see how the jetting is. You'll probably need to rejet a bit richer cuz these thing's will let it breath ALOT more.

Once your done with these and rejetted the bike it's time for more. The grey wire is really easy. Just get your manual and it'll show you exactly where it is. You can do the blue wire too. The grey wire helps with power delivery and the blue wire helps with starting & helps prevent fouling plugs. Don't need to cut them just unplug them & wrap some electrical tape around the ends. You won't see huge differences just some minor changes. For me the grey wire got rid of a sudden mid-range hit that always wanted to pull the front tire up halfway up a wide open 3rd gear climb.

Then there's the YZ timing. Takes a bit more work, but it's worth it if you ride in open country. If your in tight woods & techical single track all the time, then the WR timing might be better.

Those should give you a good start. I'm looking into the BK mod & may do that one soon too. It's supposed to help with fuel delivery off idle. Check motoman393's website. He's got all this info and more with pics.

Good luck,

I thought only 7mm should be removed from the throttle stop screw for a total length of 27mm. What I did for my 01WR426 is install a 01YZ426 throttle stop screw. It worked perfect.

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