IQ”d
FIGURE
87.
TESTING
STALL
TORQUE
High free speed with low developed torque and high
current draw indicates shorted fields. Since there is
no easy way to detect shorted field coils, replace and
check for improved performance.
The voltage drop across the solenoid on the starting
motor should be less than
0.3
volts. If not, remove it
for repair.
BATTERY
Engines with aseparatecranking motor normally use
a single 12 volt battery of at least
62
amp-hour
capacity.
The battery charging system maintains the batteries
at or near full charge at all times. Inspect the battery
charging system and adjust the charge rate if batter-
ies appear to be continually discharged.
Adding accessories that draw battery current requires an adjust-
ment
of
the
charge
rate.
If discharge or failure to charge cannot be traced to
the battery charging system, thoroughly inspect and
test the battery, and replace
it
as necessary.
REPAIR
Armature
Inspect the armature for mechanical defects before
checking for grounds or shorted coils.
To
test for grounds, use a 12volt test lamp and check
between each segment of the commutator and the
shaft. Do not touch probes to the commutator brush
surfaces, as this will burn
the
smooth surfaces.
A
growler is necessary to test for shorted coils. With
the armature on the growler, run asteel strip over the
armature surfaces. If a coil
is
shorted, the steel strip
will become magnetized and vibrate. Rotate the
armature slightly and repeat the test. Do this for one
complete revolution of the armature. If the armature
has a short or ground, replace
it.
If the commutator is only dirty or discolored, clean
it
with
00
or
000
sandpaper. Blowsand out
of
rotor after
cleaning. If, however,
it
isscored, rough orworn, turn
it down
in
a lathe.
Field Coils
Using atest lamp and probes, check the field coilsfor
grounding to themotorframe or open circuit. Inspect
all connections to be sure they are properly clinched
and soldered. Inspect the insulation for evidences of
damage.Theonlywayto check forfield coilshorts is
to use the starting motor test.
Bearings
If either the front or rear bearings show excessive
wear, replace them. Drive the old bearings out, and
using an arbor press and the proper arbor, press new
bearings into place.
Brushes
Check the brushes for wear or improper seating.
They should slide freely in their holders. Check the
brush spring tension with a spring scale. To change
spring tension, twist thespring at the holder with long
nosed pliers.
Replace Prestolite brushes when excessively worn,
or when worn to
5/8
inch in length. Replace Mitsubi-
shi, brushes when excessively worn
or when worn to
7/16
inch
in
1ength.Some brushesaresoldered to the
field coil. To remove these brushes, unsolderthe lead
and open theloop
in
the field coil lead. lnsertthe new
brush pigtail completely into the loop and clinch
before resoldering.
A
good soldering job is necessary
to ensure good contact and low voltage drop across
the connection.
Over-Running Clutch
Clean the clutch thoroughly but do not dip
in
solvent.
It
cannot be repacked with grease.
It
should slide easily on
the
armature shaft with no
binding. Turn
the
pinion;
it
should rotate smoothly,
but not necessarily freely. Reverse the direction afew
times and
it
should instantly lock and unlock. Replace
the
clutch
if
operation is defective
or
pinion is worn or
damaged.
Shifting Solenoid
See that the plunger moves freely
in
the coil. Check
pull-in coil continuity between the solenoid control
terminal and the solenoid connection to the motor.
Check the hold-in coil continuity between
the
sole-
noid control terminal and ground on the motor.
Redistribution or publication of this document,
by any means, is strictly prohibited.
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