Yamaha YFM90RA Owner's Manual page 83

1. Spark plug wrench
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.
2. Check the spark plug for electrode erosion
and excessive carbon or other deposits, and
replace it if necessary.
Specified spark plug:
NGK/CR7HSA
To install the spark plug
1. Measure the spark plug gap with a wire thick-
ness gauge and, if necessary, adjust the gap
1
to specification.
Spark plug gap:
0.6–0.7 mm (0.024–0.028 in)
1. Spark plug gap
8-10
8 8