Yamaha YFM450FAT, Owner'S Manual

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3. Use the spark plug wrench in the tool kit
to remove the spark plug as shown.
1. Spark plug wrench
Inspection
The spark plug is an important engine compo-
nent and is easy to inspect. The condition of
the spark plug can indicate the condition of
the engine.
The ideal color on the white insulator around
the center electrode is a medium-to-light tan
color for a ATV that is being ridden normally.
Do not attempt to diagnose such problems
yourself.
Instead, take the ATV to a Yamaha dealer.
You should periodically remove and inspect
the spark plug because heat and deposits will
cause the spark plug to slowly break down
and erode. If electrode erosion becomes ex-
cessive, or if carbon and other deposits are
excessive, you should replace the spark plug
with the specified plug.
Installation
1. Measure the electrode gap with a wire
thickness gauge and, if necessary, adjust
the gap to specification.
Specified spark plug:
DR8EA (NGK)
Spark plug gap:
0.6–0.7 mm (0.024–0.028 in)
U1D910.book Page 29 Thursday, May 27, 2004 11:08 AM