Arctic Cat Cougar Service Manual page 142

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as those shown, while still exhibiting the same
condition.
Normal condition
If the plug has a light tan- or gray-colored
deposit and no abnormal gap wear or erosion,
good engine, carburetion and ignition condition
are indicated. The plug is of the proper heat range
and may be serviced and returned to use.
Carbon fouled
Soft, dry, sooty deposits covering the entire
firing end of the plug are evidence of incomplete
combustion. Even though the firing end of the
plug is dry, the plug's insulation decreases. An
electrical path is formed that lowers the voltage
from the ignition system. Engine misfiring is a
sign of carbon fouling. Carbon fouling can be
caused by one or more of the following:
a. Too rich fuel mixture (incorrect jetting).
b. Spark plug heat range too cold.
c. Over-retarded ignition timing.
d. Ignition component failure.
e. Low engine compression.
Oil fouled
The tip of an oil fouled plug has a black
insulator tip, a damp oily film over the firing end
and a carbon layer over the entire nose. The
electrodes will not be worn. This condition may
occur following engine service. The oil used
during assembly, oil added to the first tank of fuel
and the oil normally injected by the injection
system may foul the spark plugs. These proce-
dures are used on a newly overhauled engine to
ensure adequate initial lubrication. The condi-
tion should be corrected by cleaning or changing
the spark plugs after using the first tank of gaso-
line/oil mix and filling the tank with gasoline.
Other causes for this condition are:
CHAPTER FOUR
a. Too much oil in the fuel (incorrect mixture
of gasoline and oil or incorrect oil pump
adjustment).
b. Wrong type of oil.
c. Ignition component failure.
d. Spark plug heat range too cold.
e. Engine still being broken in.
Oil fouled spark plugs may be cleaned in an
emergency, but it is better to replace them. It is
important to correct the cause of fouling before
the engine is returned to service.
Gap bridging
Plugs with this condition exhibit gaps shorted
by combustion deposits between the electrodes.
If this condition is encountered, check for an
improper oil type, excessive carbon in the com-
bustion chamber or a clogged exhaust port and
pipe. Be sure to locate and correct the cause of
this condition.
Overheating
Badly worn electrodes and premature gap
wear are signs of overheating, along with a gray
or white "blistered" porcelain insulator surface.
The most common cause for this condition is
using a spark plug with a heat range that is too
hot. If you have not changed to a hotter spark
plug and the plug is overheated, consider the
following causes:
a. Lean fuel mixture (incorrect main jet or
incorrect oil pump adjustment).
b. Ignition timing too advanced.
c. Cooling system malfunction.
d. Engine air leak.
e. Improper spark plug installation ( overtight-
ening).
f. No spark plug gasket.