3. Check depth of mica on commutator. If undercut is less
than 0.008 in. (0.20 mm), use an undercutting machine
to undercut the mica to 1/32 in. (0.79 mm) deep.The slots
should then be cleaned to remove any dirt or copper dust.
NOTES
• See Figure 5-2. If an undercutting machine is not available,
undercutting can be done satisfactorily using a thin
hacksaw blade. After undercutting, lightly sand the arma-
ture with crocus cloth to remove any burrs.
• Do not use sandpaper or emery cloth on commutator.The
abrasive grit may remain on commutator segments and
could cause excessive brush wear.
4. See Figure 5-3. Check for a SHORTED ARMATURE.
a. Place armature on growler (1).
b. Hold a thin steel strip (2) (hacksaw blade), against
the armature core and slowly turn armature.
c. A shorted armature will cause the steel strip to vibrate
and be attracted to the core. Replace the armature if
shorted.
5. See Figure 5-4. Check for a GROUNDED ARMATURE
with an ohmmeter or continuity tester.
a. Touch one probe to any commutator segment.
b. Touch the other probe to the armature core.
c. There should be no continuity (infinite ohms). If there
is continuity, the armature is grounded. Replace a
grounded armature.
6. See Figure 5-5. Check for an OPEN ARMATURE with an
ohmmeter or continuity tester.
a. Check for continuity between all commutator seg-
ments.
b. There should be continuity (0 ohms) at all test points.
If there is no continuity at any test point, then the
armature is open. Replace an open armature.
2008 Dyna Service: Starter 5-3
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