Fouled Spark Plug

Reader Contribution by Keith Fellenstein
Published on November 4, 2015
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Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, 1503 SW 42nd St., Topeka, KS 66609, or send an email with “Keith’s Garage” as the subject.

Fouled spark plug

Q: I have a question about my Yamaha XT500. The spark plug keeps fouling. Whether I ride it for a short time or a long time, it doesn’t matter, it still becomes black. I took the carburetor apart and cleaned the jets. I adjusted the idle screw, but after running the bike again, the plug is black. I bought the bike from someone who lived in Sacramento, California, and where I live the elevation is around 2,200 feet. Do I need to run smaller jets? How do I fix this problem? – Marvin Schaaf/via email

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