Spark Plug Inspection - Yamaha BIG BEAR YFM400NN Owner's Manual

EBU00286

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.
For example, a very white center electrode
porcelain color could indicate an intake air
leak or carburetion problem for that cylin-
der. Do not attempt to diagnose such prob-
lems yourself.
Instead, take the machine 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,
you should replace the spark plug with one
of the proper type.
Standard spark plug:
DR8EA (NGK)
Before installing the spark plug, measure
the electrode gap with a feeler gauge and
adjust to specification.
Spark plug gap:
0.6 ~ 0.7 mm (0.024 ~ 0.028 in)
a. Spark plug gap
When installing the spark plug, always
clean the gasket surface and use a new
gasket. Wipe off any grime from the
threads and tighten to the specified torque.
Tightening torque:
Spark plug:
17.5 Nm (1.75 m·kg, 12.5 ft·lb)
8-11