'01 WR 426 - 1 Mod - 2 problems

(First post, sorry if its a little long) Just want to state that I love this bike ('01 WR 426) as much as anyone could, but there are a couple of annoyances that I would not mind clearing up. Background: white brothers e-series slip-on, valves 'serviced' once, removed the throttle stop, I am not a mechanic. This bike had no problems until I put the new pipe on and then it started fouling plugs occassionally, but have never touched the carb . I then removed the the throttle stop and I was amazed at the difference (positive). I then took it to the shop to get serviced and they reccommended they adjust the valves. That is when the second problem arose. Now the bike will sometimes refuse to start, even with a new plug, and I have to wait a while until it decides its ready to start. The weird thing is that I will kick it 10 or 20 times (choke on and off) and get nothing, then all of a sudden, usually with the choke off, kick 21 and it will start like nothing ever was wrong and it settles into a nice idle. Most recently it seems that the plug fouling is more frequent and is even worse when I remove the air-box lid. Now I just do not ride it quite as hard and the plugs seem to last longer. I also now have an '03 yz 250f and therefore do not ride it as frequently, so maybe that is a factor as well. So, finally, my question is, is this a jetting issue, valve issue, garage jelousy or what? Any advice would be great. This is a great site I only found a few days ago and the answers are probably here somewhere, I just could not find them. Thanks,


Hard starting is usually a sign of valves heading out of tolerances. Fouling of the plugs is getting, usually a sign of richness.

If it were me, I'd go in an check those valves, and take a hard look at the plug. Maybe come down one size in the main jet.

Good luck!

Seems pretty weird to me that you are fouling plugs, especially with the new exhaust. Did you rejet the carb when you replaced the exhaust? If so, perhaps you went a little too far on the rick side. I have NEVER fouled a plug in my bike. If you remove your plug (during a period where the bike is running well), does it look very black? It sounds to me like a too rich situation - I would look to your jetting. I'm assuming that your air filter is not completely clogged with dirt or oil as well, as this will cause a too rich situation as well.

if already rejetted then try leaning out the fuel/air mixture screw

Jetting would be my first instinct also

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