5 replies to this topic
  • TheRainMan

Posted November 07, 2004 - 09:33 AM


I have on 02 426 that runs awesome, no smoke, no bog, it runs like a beast. The jetting is dead on for performance!
With that said, how come this bike fouls the plug after every ride? The plugs are completely black and the bike won't start until I put in a new one. Then it runs awesome and it will eventually foul the plug again and again and again and again. I don't notice any abnormal oil consumption that might contribute to the problem. Don't see how it can be a jetting problem when it runs so good!

  • jespertheil

Posted November 07, 2004 - 09:42 AM


Mine does the same. Runs great the whole day, sometimes even the next. Leave for 3 days and no go...
I have tried everything said on this forum and it´s still the same.
Try the blue wire mod and see if it works for you.
Otherwise, get use to it.... I did. :cry:

  • OldenPhatt

Posted November 07, 2004 - 10:10 AM


I have an 02 426 also and I have never fouled a single plug. I may just be lucky, but my bike backfires a bit on decelleration, which is normally a sign of slightly lean jetting, but I've had no problems whatsoever. Another thing I do is if the bike doesn't start after a few kicks, this happens most often after stalling it, I pull the de-comp lever and kick it through at least ten times to clean it out, which might also keep plugs from fouling. I'm not racing, so I'm not ringing out the motor every second, which might enable to get away with a slighty leaner jetting. Caution is urged as the downside of going too lean is rather large, but a "totally black plug" is a pretty strong indication that you're running too rich.

There is also some great info on the TT jetting forum, just do a search on "426."

Hope this helps.

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  • DoctorRzed

Posted November 07, 2004 - 10:38 AM


Ypur running it a bit rich, drop the main.

  • YZ250F_Rider

Posted November 07, 2004 - 01:56 PM


it's the AP circuit thats too rich. The AP dumps tons of wet fuel on the plug that never does burn. It carbon fouls the plug if it's too rich. Try increasing the leak jet.

  • Fastest1

Posted November 07, 2004 - 06:15 PM


If it runs great and you dont want to adjust the carb, try turning off the fuel and let it run dry before putting it up. Shouldnt have the problem anymore. :cry:

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