Yamaha YXR70FX Owner's Manual page 122

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 of the porcelain insulator
around the center electrode is a medium-to-
light tan for a vehicle that is being ridden nor-
mally.
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.
Specified spark plug:
CPR7EA-9 (NGK)
Installation
1. Measure the electrode gap with a wire
thickness gauge and, if necessary, adjust
the gap to specification.
Spark plug gap:
0.8–0.9 mm (0.031–0.035 in)
a. Spark plug gap
2. Clean the surface of the spark plug gas-
ket and its mating surface, and then wipe
off any grime from the spark plug
threads.
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