Yanmar 4LHA-HTP Operation Manual page 638

Chapter 9 Electrical System
3. Starter Motor
6 Inspection
6.1 Armature
(1) Commutator
Inspect the surface of the commutator. If corroded or
pitted, sand with #500 ~ #600 sandpaper. If the
commutator is severely pitted, grind it to within a surface
roughness of at least 0.1 mm (0.0039 in) by turning it on a
lathe. Replace the commutator if damage is irreparable.
Model
Commutator
outside diameter
Deflection
(2) Mica undercut
Check the mica undercut, correct with a hacksaw
blade when the undercut is too shallow.
Bad
Hacksaw blade
Commutator
Commutator
S e g m e n t m i c a
Bad
Maintenance
standard
0.2
Mica undercut
(0.0079)
Sand paper
SI 3-41A
Maintenance
Wear limit
standard
036.6(1.4409)
038(1.4961)
Repair accuracy
Repair limit
0.05(0.002)
0.1 (0.0039)
Good
Hacksaw blade
" 0.5 ~ 0.8 mm
F a C i 9
Good
mm (in.)
Repair limit
0.5 ~ 0.8
(0.0197 ~ 0.0315)
(3) Armature shaft outside diameter
Measure the outside diameter of the armature shaft at
four locations: front, center, end, and pinion. Replace the
armature if the shaft is excessively wom.
Check the bend of the shaft; replace the armature if the
bend exceeds 0.08mm (0.0031 in)
Front side
Armature shaft Armature shaft
diameter diameter
Rear side
(4) Armature coil continuity and ground test
Using a tester, check for continuity between the
commutator and the shaft (or armature core). Continuity
indicates that these points are grounded and that the
armature must be replaced.
Checking commutator for insulation defects.
Checkpoint
Kind oftest
Commutator
Continuity
between armature
Commutator
Insulation between armature
or shaft
9-12
i 4LHA Series
mm (in.)
Maintenance
Repair limit
standard
025(0.9843) 024.90(0.9803)
012(0.4724) 011.90(0.4685)
Normal Abnormal
NO (Broken or
YES
disconnected coil)
YES (Short-circuit)
NO