I own a 2002 wr 426 and was wondering if I uncork the exhaust, use yz throttle stop, take air lid off, and cut grey wire, can I stay with stock jetting. Can there be any negative effects to your motor with these mods (if staying stock jetting). Any info will be greatly appreciated.

Has anyone done the 4 mods without rejeting, or if rejeted, what to? Does bike run leaner or richer with mods. So far really like my 2002 wr 426.

I have done all those to my 00wr400 and did not find any reason to rejet. It runs perfect, crisp, snappy throttle response.

From what I understand the bike runs hot with the stock baffle in. Many magazines stated that the bike is not intended to be operated like that.

Others may prefer to change the jetting to get more power etc. But it is not necessary.

Do the mods you listed and discover how the bike was really intended to run. It will rip.

I forgot to mention you can just cut the throttle stop with a dremel tool or hack saw to the right length. Looks thru the archives for the correct length.

I have been racing and riding mine for two years and had zero problems.

Thanks for the information.

I was also wandering if you happen to know when is the best time to check your sparkplug to see if your running rich or lean, hot or cold, or does it matter.


I have an '02 426 with the 4 mods done and I have the jets to do th re-jet but i don't feel the need after the 4 mods I've done (that and i'm lazy). My bike Runs great.It's not as fast as my buddies , Who has the same bike with the jetting and timing done (plus a few cosmetic items) but there is also a 40lbs. diff between us and he doesn't pull from me that much ... One of these days i will get around to re-jetin my bike but, I am having no problems with the way it is . Only reason i will re-jet is to add to my signature! (lol jk)

good luck ...ride safe!


well this all sounded so wonderfull i did them removed the airbox lid pulled the baffel cut the grey wire the one on the black connector and the blue wire for eaiser starting and did the throttle stop and mine runs terrible so i put the airbox lid back on and put the baffel back in and it still runs terrible so i left the airbox lid on and removed baffel agian still runs terrible was i not supposed to cut the blue wire could this be my problem???? i cant even get it back to where it was stock its running worse than it did out of the box what did i do wrong it dies if i give it full throttle i can only open the throttle about 1/4 for it to run very well at all HELP this thing has know guts at all i am bummed my buddy did the same stuff to his and it rocks thats why i bought it but i must be missing somthing here or maybe i removed the wrong wire i dont know im am frustrated now time to quit for the day and try agian tommarrow this thing is a whimp and i know it shouldnt be.

On my 2002 wr 426, So far I pulled baffle and put yz throttle stop in. Bike is up north, so next time up I will be cutting gray wire and removing air lid, however so far my bike runs to my satisfaction with just the the 2 mods. I haven't heard anything about cutting a blue wire, so maybe that might be your problem. Is your or your bodies bike jetted or stock? I'm not to much of a mechanic, so whatever mods I do make, I want to do without messing with the carb, or at least for a while. Also, did you check your spark plug to see if running rich or lean?

Blacksunday, I have an '02 and only did the airbox lid, exhaust baffle, throttle stop, and grey wire mods and my bike runs great. I know for YZ's they have a blue wire mod, but I didn't know WR's had one. That might be your problem.

[ July 26, 2002: Message edited by: Red-eyed Demon ]

thanks guys that may very well be my problem got a little carried away with the mods i guess, did them all at once but the blue wire is supposed to improve spark in neutral on wr also according to motoman393 check it out

when you go there check out the tech section and the read the article on make your yzf start eaiser and it says it is also for wr i just dont want to tear the tank back off unless i have to but i guess thats the only thing left is to reconnect the wires and see what happens unless anyone has any ideas i am running stock jetting and will pull the plug to day after work to check it

[ July 26, 2002: Message edited by: blacksunday12101 ]

Make your YZF start better

If you are fouling plugs, or have trouble starting your YZF then this mod is for you! This mod works on 98-02 YZ/WR250f, YZ/WR400f, and the YZ/WR426


To do this mod all you need to do is remove the light blue wire from the CDI. This light blue wire goes to the neutral switch and is causing low voltage output out of the cdi when it neutral. So when you disconnect the wire you get more voltage in neutral and more spark=easier starting. It takes some wiggling around to get the wire out (WD-40 and compressed air helped loosen all the dirt and made it easier to remove) You DONT cut the wire you simply unhook it. Make sure you wrap electrical tape around the wire (in case you ever want to plug it back in)

Now go amaze your 2 stroke buddies and fellow YZF owners by how easy your bike starts w/o fouling plugs.

well in an effort to solve my problem i went ahead and pulled the carb off and changed the main jet went from stock 165 to a 168 and did the bk mod while i had it off also slowed the accelerator pump timing to come in later and decreased the spry length to about .35 and it is still running like a dog it didnt seem to make any difference. now i am really starting to wonder about the wire mods and if they are correct for this 2002 wr426 anyone have any ideas or should i just take it in and have it professionaly done ?


Put the blue wire back in. Make sure no other wires are disconnected. You may even want to fix the grey wire.

I have an 02 426. I did rejet, but, I also did the other mods first. (except the blue wire)

I found a noticeable difference when I got rid of the airbox lid, and again when I switched to the vortip exhaust, and again when the throttle stop was cut. I DID NOT find that much difference with the grey wire cut. However, the best mod I did was REJET. My bike can pull up the front wheel almost at will. No one wants to ride behind me anymore. They are tired of getting pelted with debris.

Also, according to all sources, these bikes come stock from the factory rich. So I am not sure going with a larger MJ is what you want to do. I am no jetting expert, but, I know that jetting is easy and needle changes are easy. just don't be intimidated if you have never done this before. DO NOT use my jetting as a comparison because of the altitude difference.

Last, it seems like all these bikes have their own quirks and personalities. Get used to snatching off the seat and the tank. You will be doing it a lot until you get your ride dialed in. Once you do get it dialed in, start doing shoulder and arm excersices to keep your arms from being pulled out of their sockets. LOL

If anyone has any different advice or if I have mis-spoken, make sure you let blacksunday know. nothing is more frustrating than a new bike that wont run right.


i have had it every mod i do makes it worse thats it i am going to find someone that knows what the hell they are doing i guess i sure dont even if i can make my cr scream and have built entire engines from the ground up i cant seem to get this damn bike to run right my damn lawnmower is faster should have bought something else right now i am sure feeling like i wasted my money on this bike it bogs it pops it bacfires and nothing changes right now i am so not glad i bought it my brother is comming over tomarrow he is a certified mechanic if we cant get it to run right then i dont know what to do.

[ July 26, 2002: Message edited by: blacksunday12101 ]

Re-connect the blue wire.

well now i am back to where the jetting changes have effect i do not care what is said about the blue wire dont do it on a 02 wr 426 or it will drive you crazy i believe that i can now get this bike dialed in will continue to play with jetting tomarrow re-connecting the blue wire made alot of difference why would someone reccomend this it may be fine for the yz but the article i read on motoman393`s site it clearly states that this is also for 20 wr426 well i guess not it may be fine for the yz but i would not recomend this for wr`s

anyone got a good starting point where my settings should be for my carb in michigan bike is a 2002 wr426 MJ 168 all others are stock airbox lid removed stock pipe baffel out grey wire cut and yz throttle stop any ideas thanks

[ July 27, 2002: Message edited by: blacksunday12101 ]

I also ride in Michigan, and am interested in other 2002 wr 426 owners that have the free 4 mods done, on what there jetting is for Michigan.

Originally posted by Team Oatmeal Pie:

I have done all those to my 00wr400 and did not find any reason to rejet. It runs perfect, crisp, snappy throttle response.

Ditto, zero problems at Socal elevation with stock jetting, Lid off, WR timming, BK mod. Euro/Canadian model: No throttle stop, No grey wire. Pro-Circuit T4.

I've tried to rejet my bike with other spec's with worse results. I would love to be in the jetting club but rejetting never worked out with my WR timmed bike. When ever my bike does sputter it's usually because my carb is dirty and my air filter needs a cleaning.

DL :)

ps dan what about the ACV MOD did you or have you tried that one.

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