IGNITION SYSTEM
56
5. Inspect the key, keyway, and tapered mating sur-
faces of the flywheel and crankshaft.
NOTE: If the key is damaged, it must be
replaced. If there is damage to the crankshaft,
the engine must be short blocked because the
crankshaft is not available as a service part.
NOTE: On installation, confirm that the key is
properly seated (the flat of the key parallel with
the threaded section of the crankshaft) in the
keyway, and that the tapers are fully seated.
Key or keyway failure may result from improper
seating.
IMPORTANT: The tapers in flywheel and on the
crankshaft must be clean and dry. The flywheel
is held in place by the friction between the fly
-
wheel and the crankshaft, not the key. The key is
only to guide the flywheel to the proper position
until it is torqued down.
6. Install the flywheel nut to a torque of 47-52 ft-lbs.
(64-70 Nm).
7. Adjust the air gap by following the steps
described in the previous section of this chapter.
8. Reassemble the engine.
9. Test run the engine before returning to service.
About the spark plug
• The spark plug is a Torch model F6RTC, gapped
to .026”-.030” (0.65-0.75 mm).
• Champion RN14YC or NGK BPR4ES are physi-
cally similar but do not match the F6RTC in heat
range. This difference in heat ranges will effect
performance and emissions. It is recommended
that the Torch F6RTC plug be used for service.
• Wear rate will vary somewhat with severity of
use. If the edges of the center electrode are
rounded-off, or any other apparent wear / dam-
age occurs, replace the spark plug before oper-
ating failure (no start) occurs.
Cleaning the spark plug
• Cleaning the spark plug is not recommended. If
the plug needs to be cleaned, replace it.
• Use of a wire brush may leave metal deposits on
the insulator that cause the spark plug to short-
out and fail to spark.
• Use of abrasive blast for cleaning may damage
the ceramic insulator or leave blast media in the
recesses of the spark plug. When the media
comes loose during engine operation, severe
and non-warrantable engine damage may result.
Inspection of the spark plug
Inspection of the spark plug can provide indications
of the operating condition of the engine.
• Light tan colored deposits on insulator and elec-
trodes is normal.
• Dry, black deposits on the insulator and elec-
trodes indicate an over-rich fuel / air mixture (too
much fuel or not enough air)
• Wet, black deposits on the insulator and elec-
trodes indicate the presence of oil in the com-
bustion chamber.
• Heat damaged (melted electrodes / cracked
insulator / metal transfer deposits) may indicate
detonation.
• A spark plug that is wet with fuel indicates that
fuel is present in the combustion chamber, but it
is not being ignited.
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