Spark Plug Inspection - Yamaha XTZ 125K Owner's Manual

Spark plug inspection

The spark plug is an important engine component and is
easy to inspect. The condition of the spark plug can indicate
the condition of the engine.
The ideal color on the white porcelain insulator around the
center electrode is a medium to light tan color for a
motorcycle that is being ridden normally. Do not attempt to
diagnose any problems yourself. Instead, take the
motorcycle 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 excessive, or if carbon and
other deposits are excessive, you should replace the spark
plug with the specified plug.
Standard spark plug:
CR7HSA (NGK) and U22FSR-U (DENSO)
Before installing the spark plug, measure the electrode gap
with a wire thickness gauge and adjust the gap to
specification as necessary.
Spark plug gap:
0.7 mm ( 0.028 in)
When installing the plug, always clean the gasket surface
and use a new gasket. Wipe off any grime from the threads,
and torque the spark plug properly.
Spark plug torque:
12.5 N.m (1.25 Kgf.m, 9 lbf.ft)
NOTE:
If a torque wrench is not available when you are installing a
spark plug, a good estimate of the correct torque is 1/4 to
1/2 turn past finger tight. Have the spark plug torqued to
the correct value as soon as possible with a torque wrench.
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