Tool Kit; Checking The Spark Plugs - Yamaha VK10A Owner's Manual

Periodic maintenance and adjustment
ESU13470

Tool kit

The service information included in this man-
ual and the tools provided in the owner's tool
kit are intended to assist you in the perfor-
mance of preventive maintenance and minor
repairs. However, additional tools such as a
torque wrench may be necessary to perform
certain maintenance work correctly.
1. Tool kit
ECS00960
NOTICE
Before starting the engine, make sure that
the tools are properly seated in their hold-
er.
TIP
If you do not have a torque wrench available
during a service operation requiring one, take
your snowmobile to a Yamaha dealer to
check the torque settings and adjust them if
necessary.
ESU11783

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
42
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:
CR8E
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
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)