Replace it if necessary.

Inner Tube Inspection
Spring Tension InspectionPiston Removal
Remove:
Crankshaft (see Crankshaft Removal)
Remove the piston together with the connecting rod to the
cylinder head side.
NOTICE
Discard the connecting rod bolts and nuts. To prevent
damage to the crankpin surfaces, do not allow
the connecting rod bolts to bump against the
crankpins. ...
Armature Inspection
Using the × 1 Ω hand tester range, measure the resistance
between any two commutator segments [A].
Special Tool - Hand Tester: 57001-1394
If there is a high resistance or no reading (∞) between any
two segments, a winding is open and the starter motor
must be replaced.
...
Alternator Rotor Installation
Using a cleaning fluid, clean off any oil or dirt on the following
portions and dry them with a clean cloth.
Crankshaft Tapered Portion [A]
Alternator Rotor Tapered Portion [B]
Install the alternator rotor.
Using a cleaning fluid, clean off any oil or dirt on the
washer [A] ...