TM 5-4240-5501-148P
STARTERS
Gear Drive 12V & 120V
Checking Starter Motors
If a starting problem is encountered, check the engine
thoroughly to be sure it is not the cause of starting
difficulty. It is a good practice to remove the spark plug
and rotate the crankshaft by hand, to be sure it rotates
freely. Any belt, clutch or other parasitic load will affect
cranking performance.
Service procedures for both the 12 volt and 120 volt
starter motors are similar and will be covered together,
except where noted otherwise.
A list is provided to aid in diagnosing problems for 12 volt
DC and 120 volt AC systems. See page 9 and 10.
CHECKING STARTER MOTOR DRIVE
When the starter motor is activated, the pinion gear
should rise, engaging the flywheel ring gear and crank
the engine. This action can be observed by removing
the starter shield. If the starter motor drive does not
react properly, inspect the helix and pinion gear for
freeness of operation. If any sticking occurs, this must
be corrected. Proper operation of the starter is
dependent on the pinion freely moving on the helix. See
Fig. 109.
Fig. 109 - Checking Starter Motor Drive
DISASSEMBLING STARTER MOTOR DRIVE
To
remove
the
drive
assembly
for
cleaning
or
replacement, clamp the pinion gear in a vise having
brass jaws, to prevent damage to the gear teeth. The
lock nut may then be removed and the starter drive
disassembled for cleaning or replacement.
The pinion gear should be inspected for damaged teeth.
If a sticking condition exists between the pinion gear and
the helix, the parts may be washed in a solvent such as
Stanasol or Varsol. If the sticking condition is not
corrected by cleaning, the complete drive assembly must
be replaced. Individual parts of the drive assembly are
not available.
ASSEMBLING STARTER MOTOR DRIVE
Reverse disassembly procedure for assembling. The
interior of the shaft screw has a spline machined to the
center; when assembling, the spline must face the end of
the armature shaft. See Fig. 110. Torque the lock nut
to 170 inch pounds (19.2 Nm). This torque has an effect
on pinion travel, so proper torque should be maintained.
NOTE: Do not lubricate Drive Assembly.
NOTE: For starter motors equipped with nylon pinion
gear, page 24 and 25 contains assembly and repair
information.
Fig. 110 - Assembling Starter Motor Drive
If sticking occurs during freezing weather, spray
a dry silicone spray on helix.
CHECKING STARTER MOTOR
PERFORMANCE
120 VOLT AC STARTER MOTORS
A performance test of the 120 volt starter motor may be
made in the following manner.
Equipment Needed
1. A tachometer capable of reading 10,000 RPM.
2. An ammeter capable of reading 0 to 10 amperes.
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