Fouled Plug

I just bought my son a 2005 yz85 and he is just learning to ride the new

bike and is not riding it too hard and is having a problem of fouling the plug.

What can anybody suggest i do to stop this from hapening.Should i turn in the pilot air screw adustment to lean it out a little? Or any other suggestions.

Other than that the bike runs great.I am also mixing the fuel at 36 to 1

try dropping the main jet one size at a time.

you don't think i sould change the pilot air screw?

My boy's 65 was similar and I dropped the needle one notch, you may even go a size smaller on the idle jet too. If he isn't opening it up you need to cut back on the fuel. 0 to half throttle is mainly your air fuel screw, slow idle jet and your needle position in the main jet in that sequence. Dropping the needle and adjusting the air/fuel screw cost $0.00.


I'm not quite sure how to drop the needle at this time so do you think ajusting the pilot air screw alone will help?

Not really, The owners manual should have a step by step description on how to do it. It not too bad especially on the smaller bikes.

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