Section 3 Engine Diagnostic Tests
Diagnostic Repair Manual
35
Flywheel Key
In all cases, the flywheel’s taper is locked on the
crankshaft taper by the torque of the flywheel nut. A
keyway is provided for alignment only and theoretically
carries no load.
If flywheel key becomes sheared or even partially
sheared, ignition timing can change. Incorrect timing can
result in hard starting or failure to start.
Test 27 – Check Flywheel
General Theory
See
. In Test 20, a spark tester was used to
check for engine ignition. If sparking or weak spark
occurred, a possible cause might be the ignition
magneto. This test checks magnetism of flywheel and will
check the flywheel key.
Figure 1-14. Engine Ground Harness
Procedure
1.
Check flywheel magnet by holding a screwdriver at
extreme end of handle with its point down. When
the tip of screwdriver is moved to within 3/4 inch
(19mm) of magnet, the blade should be pulled in
against the magnet.
2.
For rough running or hard starting engines, check
flywheel key. The flywheel’s taper is locked on the
crankshaft taper by the torque of the flywheel nut.
A keyway is provided for alignment only and
theoretically carries no load.
NOTE:
If flywheel key becomes sheared or even partially
sheared, ignition timing can change. Incorrect timing can
result in hard starting or failure to start.
Test 28 – Remove Shutdown Wire
General Theory
A single wire is used to shut down the unit when either
the switch is placed in OFF, or a low oil condition occurs.
A ground is applied to the magneto in both instances
which inhibits spark and shuts down unit. If a short to
ground exists on this wire, the engine will be inhibited
from producing spark. This test will check the integrity of
the wire.
Procedure
1.
Turn off fuel supply.
2.
Remove flywheel cover (blower housing) so
magneto is exposed.
3.
See
. Disconnect Wire 18 from
magneto.
4.
Repeat Test 20, “Check Ignition Spark”.
Results
1.
If spark now occurs, the shutdown wire has a short
to ground. Trace the shutdown wire back to
START-RUN-STOP switch and Oil Pressure Mod-
ule (if equipped).
2.
If spark still does not occur, refer to flow chart.
Figure 1-15. Wire 18
Test 30 – Check / Adjust Governor
(Mechanical)
General Theory
Rotor operating speed and AC output frequency are
proportional. The generator delivers a frequency of 60
Hertz at 3600 Rotor rpm or 62 Hertz at 3720 rotor rpm.
The voltage regulator should be adjusted to deliver 120
VAC (line-to-neutral) at a frequency of 60 Hertz or 124
VAC (line-to-neutral at 62 Hertz. It is apparent if governed
speed is high or low, AC frequency and voltage will be
correspondingly high or low. Governed speed at no-load
is usually set slightly above rated speed of 60 Hertz (to
62 Hertz) to prevent excessive rpm, frequency, and
voltage droop under heavy electrical loading.
Governor Adjustment
1.
Loosen GOVERNOR CLAMP BOLT.
2.
Push Spring end of GOVERNOR LEVER
clockwise to wide open throttle position of lever.
a. Hold GOVERNOR LEVER at wide open
