Checking The Spark Plugs - Yamaha FX Nytro FX10D Owner's Manual

ESU11784

Checking the spark plugs

The spark plugs are important engine compo-
nents and are easy to inspect. The condition
of the spark plugs can indicate the condition of
the engine.
Check the coloration on the white porcelain
insulator around the center electrode. The
ideal coloration at this point is a medium-to-
light tan color for a snowmobile that is being
ridden normally. If any spark plug shows a
distinctly different color, there could be some-
thing wrong with the engine. For example, a
very white center electrode porcelain color
could indicate an intake track air leak or car-
buretion problem for that cylinder. Do not at-
tempt to diagnose such problems yourself.
Instead, take the snowmobile to a Yamaha
dealer for inspection and possible repairs.
You should periodically remove and inspect
the spark plugs because heat and deposits
will cause any spark plug to slowly break
down and erode. Consult a Yamaha dealer
before changing to a different type of spark
plug.
Specified spark plug:
Manufacturer:
NGK
Model:
CR9E
EWS00710
WARNING
Be sure to use the specified spark plug
and spark plug cap. Otherwise, the
T.O.R.S. may not work properly.
Spark plugs are produced in several different
thread lengths. The thread length or reach is
the distance from the spark plug gasket seat
to the end of the threaded portion. If the reach
is too long, overheating and engine damage
may result. If the reach is too short, spark plug
Periodic maintenance and adjustment
fouling and poor performance may result. Al-
so, if the reach is too short, carbon will form on
the exposed threads resulting in combustion
chamber hot spots and thread damage. Al-
ways use a spark plug with the specified
reach.
Spark plug reach:
19.0 mm (0.75 in)
1. Spark plug gap
2. Spark plug reach
Before installing any spark plug, measure the
spark plug gap with a wire thickness gauge
and adjust to specification.
Spark plug gap:
0.7–0.8 mm (0.028–0.031 in)
When installing the spark plug, always clean
the gasket surface. Wipe off any grime from
the threads and tighten the spark plug to the
specified torque.
Spark plug tightening torque:
13 Nm (1.3 m·kgf, 9.4 ft·lbf)
ECS00382
NOTICE
Make sure that the spark plug caps are se-
curely installed. Otherwise the spark plug
caps could be damaged due to engine vi-
bration.
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