Help, my 426 has started fouling plugs.....

The last time I took my bike out (two weeks ago) it fouled two plugs, and then I got it out this past Saturday and it fouled another plug. It has never done this before. The bike had the carb tuned in November with the oxygen sensor, had been running great until now. It had the same plug in it four six months. Any help or guidance you guys could lend is greatly appreciated.

I heard a guy out at the track saying he heard that the YZ426 was hard needles over time. Is there any truth to this?

Thank you for your help,


Is the plug oily or more gas on the threads

You can tell by looking at the needle if its worn any. I had a 00 426 and never had any problem with it. It is probably just a small minor thing like air screw or the jetting.

I know the with mine if the pilot was to rich I would have problems at tracks with mine.

the plugs are completely black. Why would the air screw suddenly need adjustment or the pilot jet changed?

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