Mercury 100 FourStroke, Service Manual

Page: 102 / 574

2B-20 - ELECTRICAL 90-830234R3 DECEMBER 1997
4. Remove components from armature.
d
e
c b
a
f
g
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a - Locknut
b - Spacer
c - Spring
d - Drive Assembly
e - Drive End Cap
f - Armature Shaft
g - Washer
Starter Cleaning, Inspection and
Testing
CLEANING AND INSPECTION
1. Clean all starter motor parts.
2. Check pinion teeth for chips, cracks or excessive
wear.
3. Replace the drive clutch spring and/or collar if
tension is not adequate or if wear is excessive.
4. Inspect brush holder for damage or for failure to
hold brushes against commutator.
5. Replace brushes that are pitted or worn to less
than 1/4
″
(6.4mm) in length.
6. Inspect the armature conductor (commutator bar
junction) for a tight connection. A loose connec-
tion (excessive heat from prolonged cranking
melts solder joints) results in a burned commuta-
tor bar.
7. Resurface and undercut a rough commutator as
follows:
CAUTION
Do not turn down the commutator excessively.
a. Resurface the commutator and undercut the
insulation between the commutator bars
1/32
″
(0.8mm) to the full width of the insula-
tion and so that the undercut is flat.
b. Clean the commutator slots after undercut-
ting.
c. Sand the commutator lightly with No. 00
sandpaper to remove burrs, then clean the
commutator.
d. Recheck the armature on a growler for shorts
as specified in the following procedure (“Test-
ing”).
8. Open-circuited armatures often can be repaired.
The most likely place for an open circuit is at the
commutator bars, as a result of long cranking pe-
riods. Long cranking periods overheat the starter
motor so that solder in the connections melts and
is thrown out. The resulting poor connections
then cause arcing and burning of the commutator
bars.
9. Repair bars, that are not excessively burned, by
resoldering the leads in bars (using rosin flux sol-
der) and turning down the commutator in a lathe
to remove burned material, then undercut the
mica.
10. Clean out the copper or brush dust from slots be-
tween the commutator bars.
11. Check the armature for ground. See the following
procedure (“Testing”).
Testing
ARMATURE TEST FOR SHORTS
Check armature for short circuits by placing on growl-
er and holding hack saw blade over armature core
while armature is rotated. If saw blade vibrates, ar-
mature is shorted. Recheck after cleaning between
commutator bars. If saw blade still vibrates, replace
armature.
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