Yanmar 3TNV Series Service Manual page 163

(d) Armature and commutator run-out
Use a dial gage and measure the armature core
run-out and commutator run-out. Correct or replace if
the limit is exceeded.
Standard
Armature
Commutator
(e) Commutator surface inspection
If the commutator surface is roughened, grind with
#500 to #600 emery cloth.
(f) Commutator insulation depth
Measure the depth of the insulating material between
commutator segments, and correct it if it is less than
the limit.
Standard
0.5 0.8
Limit
0.03 0.2
0.03 0.2
mm
Limit
0.2
mm
148
9. Starting Motor