Checking The Spark Plugs - Yamaha PZ50W Owner's Manual

CAUTION :
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Make sure that all cables, leads, etc., are routed
properly before installing the covers.
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NOTE:
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When installing the covers, be sure to tighten the quick
fasteners and the quick fastener screws securely.
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ESU03681

Checking the spark plugs

The spark plug is an important engine component and is
easy to inspect. The condition of the spark plug can indi-
cate 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 a light
tan color for a snowmobile that is being ridden normally.
If a spark plug shows a distinctly different color, there
could be something wrong with the engine. For example,
a very white center electrode porcelain color could indi-
cate an intake track air leak or carburetion problem for
that cylinder. Do not attempt 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 plug because
heat and deposits will cause a spark plug to slowly break
down and erode. Consult a Yamaha dealer before chang-
ing to a different type of spark plug.
Specified spark plug:
R CR9EKB (NGK)
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. Also, if the
reach is too short, carbon will form on the exposed
threads resulting in combustion chamber hot spots and
thread damage. Always use a spark plug with the speci-
fied reach.
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