Greetings fellow Thumpers!!!!

Own a new 2001 WR426, muffler plug is removed, throttle stop cut down (dealer did it for me), grey-wire mod completed, air-box cover removed, otherwise stock (never adjusted jetting, etc). Only about 250 miles on her and have been changing plugs every other ride (won't start without changing one). Plugs that I remove are black but no heavy build up, bike runs fantastic when running, next day won't fire up just sputters and dies. Won't start with choke on, am I too rich or did removing my air filter lid throw me off or something? Or am I just stupid????

As soon as I get a new plug installed, first kick, VAROOM!!!! Next time I go to ride, no luck. I live in the midwest, Illinois and have not tinkered with the jetting or anything, what happened all of a sudden? Is my plug suppossed to be tan in color, mine is charcoal black, only one ride on it.

My air filter is clean and my carb is set up as I got it from the factory, never had any problems before now. I want to cry, I am frustrated and fear dumping her out somewhere on the side of a mountain and then no start (OUCH).

Thanks in advance for the info!


[This message has been edited by fourstroker (edited October 07, 2001).]

[This message has been edited by fourstroker (edited October 07, 2001).]

Stroker, I too have a 01 WR426 with the box cover removed, grey wire clipped, and stock muffler plug removed. After doing these mods I took it to a pro shop, he rode it, tested the exhaust and decided that it really didnt need anything done to the jetting. I didnt beleive him but what the hell, I rode it for two weeks anyway. ran well, took the plug out and she is a wonderful golden brown color. Couldnt ask for better tuning from the factory. Strange but true. just my .02 cents worth.



oh yeah i live in Minnesota.

Everybody I know no matter if it's a 426F, 400F, or 250F, we all had problems with plug fouling until we got 5 to 10 hours of riding time on them and then they cleared up on their own. My 400 plug is still black everytime I change it, but no longer fouled. It runs good so I'm not going to lean it out. I'd rather it be a little rich, than burn a valve up by being to lean.

Bonzai grin.gif


1999 WR 400F:

Headlight Removed,Odo Removed,Gray Wire - Cut,Throttle Stop - Trimmed,YZ Timing,GYT-R Pro-Bend Hand Guards /Tripple Clamp Mounts,YZ Front/Rear Fender,YZ Number Plate,Race Tech Suspension(by MXTuner),Dunlop 756 Front and Rear,Renthal Fat Bars W/GYT-R Pad,Renthal 14/53 Gearing,DID Race Chain

Custom Grips,Graphics by CEET,White Brothers E-Series Exhaust,Modified Compression Release,Acerbis Frame Guards

Never had a fouled plug in about 3,000 miles.

But last time I washed the bike, I didn't start the engine up afterwards. Next week was the bike didn't start, for the first time ever. So I changed the plug and it started right up.

Just a thought.


2000WR - EKN#5, 172MJ, 226MAJ, MAJ Passage drilled to 278, 48PJ, 100PAJ, YZ timing, BK mod, 3/4 turn pilot screw, DSP tapered header and pipe, IMS tank & YZ seat, Scotts dampener & triple clamp & Renthal Fatbar 971, White Bros suspension, Dunlop 756's.

its your jetting,my brother had the same prob w/his , get some more miles on her though you want to make sure she well broke in other wise you'll be messin w/the jetting for a while (which he did on his wife wr250f they had about 75 miles on it , started messin w/the jetting then all h*LL broke lose , no motor damage but just wouldnt start at all!!!)just my .02.... remember thumpers or nuthin !!!!! alan

Same problems I had. For starters, read your manual and learn about the carb. Then take the carb out and raise the clip one position (will cause the needle to drop and lean it out a bit). I had this progressively richening problem as you describe eventuallly causing a fouled plug after about 20 minutes of riding. I finally went to position #2 with the clip and have been trouble free for several months.

I wouldn't be too concerned about running too lean. The syptoms your describing show you are WAY too rich now. I haven't gotten any indication mine's running lean yet, but when and if I do, I'll just raise the needle again.

Believe me, I know how you feel, I still have lumps on my forehead from banging my head on the wall. Good Luck.

All advise given is good, but you did not indicate what octane of fuel you are running with.. IM using 110 leaded race fuel, no problems what so ever of fouling... usually, staying with 93 octane (Amoco) helps alot...try one clip on needle to lean one step and ride ...



90 Hawk

88 K75S

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