8-9
8
EBU23215
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 and lubri-
cation 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.
2. Remove the spark plug as shown, with the
spark plug wrench included in the tool kit.
To check the spark plug
1. Check that the porcelain insulator around the
center electrode of the spark plug is a medi-
um-to-light tan (the ideal color when the ATV
is ridden normally).
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.
1. Spark plug cap
1
1. Spark plug wrench
1
UBD364E0.book Page 9 Monday, January 28, 2019 9:30 AM
Summary of Contents for YFM90 2019
Page 2: ...DIC183 Original instructions Notice originale Manual original PRINTED IN TAIWAN 2019 01 E F S ...
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Page 56: ...7 1 7 EBU21142 RIDING YOUR ATV UBD364E0 book Page 1 Monday January 28 2019 9 30 AM ...
Page 123: ...11 2 11 1 Model label 1 UBD364E0 book Page 2 Monday January 28 2019 9 30 AM ...