Checking The Spark Plug - Yamaha YFM 90 2021 Owner's Manual

EBU23216

Checking the spark plug

The spark plug is an important engine component,
which is easy to check. Since heat and deposits
will cause any spark plug to slowly erode, the
spark plug should be removed and checked in ac-
cordance with the periodic maintenance chart. In
addition, the condition of the spark plug can reveal
the condition of the engine.
To remove the spark plug
1. Remove the spark plug cap.
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1. Spark plug cap
2. Remove the spark plug as shown, with the
spark plug wrench included in the tool kit.
1. Spark plug wrench
To check the spark plug
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1. Check that the porcelain insulator around the
TIP
If the spark plug shows a distinctly different color,
the engine could be operating improperly. Do not
attempt to diagnose such problems yourself. In-
stead, have a Yamaha dealer check the ATV.
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center electrode of the spark plug is a medi-
um-to-light tan (the ideal color when the ATV
is ridden normally).
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