Gravely Convertible 10 Shop Manual page 27

COMPACT STARTING MOTOR (C-10A and C-12)
The compact starting motors used with magneto-alternator (ignition and battery charging) systems,
use Bendix type drives to engage and disengage from the engine.
OPERATION: When the starting circuit is closed and the armature starts to rotate, the Bendix drive
pinion moves laterally on a splined sleeve into mesh with the flywheel ring gear. When the pinion butts
against a stop washer at the end of the armature shaft, the pinion rotates along with the armature to crank
the engine. The armature and pinion remain in positive engagement until the engine fires and attains the
speed where the flywheel begins overriding the armature. At this instant, the greater momentum of the
flywheel throws the pinion out of mesh and back into the retracted or disengaged position. After the
starting circuit is opened and as the armature coasts to a stop, a small spring holds the pinion in the
retracted position.
PRECAUTIONS: In the event of a "false start", that is, if the engine gets up sufficient speed to disengage
the starter but fails to continue running, the engine must be allowed to come to a complete halt before a
restart attempt is made. If the flywheel is still rotating when the starter is engaged, the pinion and ring gear
will clash and almost certainly be damaged.
Also, as with all starting motors, the cranking time must be limited to prevent overheating of the
starter. On these compact starters, the maximum time allowed for cranking is 60 seconds followed by a 30
second cooling period. The cranking limit is not unreasonable for if an engine fails to start after this length
of time, ignition or carburetion troubles are indicated and these should be corrected before the engine is
placed in operation.
SERVICE: These starters are pre-lubricated during assembly and further lubrication is not normally
needed until the starter is partially diassembled for brush or commutator servicing. These services are not
required at any specific hourly basis -- they should be performed only after starter performance indicates
the need of such service. Instructions for brush, commutator and lubrication service fallow the Trouble
Analysis Chart.
The end cap assembly must be removed to inspect and service the brushes and commutator. Remove
the two thru bolts then carefully slip end cap off end of armature. Lift spring and remove positive brush
from holder if complete removal of end cap is necessary.
Brush-Commutator Service: Use a coarse cloth to clean brushes and commutator. If commutator is
grooved or extremely dirty, use a commutator stone or fine sandpaper to polish -- do not use emery cloth.
Brushes should be replaced if unevenly worn or worn to lest than 5/16" in length. Brush replacement is
made with a new Brush Kit. The rivet must be drilled out and the new brush riveted in its place. Make sure
good mechanical and electrical contacts are made. Positive brush is affixed to field winding. Peel back
insulating material, remove old brush. Solder or clip new brush to same spot rewrap insulating material
around new joint.
End Cap Installation: Before reassembling new or serviced end cap assembly, lightly coat bushing and
end of the armature shaft with SAE No. 10 oil -- make sure there is no excess of oil to splatter from these
parts. Insert positive brush in a holder. Hold positive brush spring away with a needle nose pliers, then
carefully guide end cap into position - release brush spring after brushes are started on commutator. Secure
end cap to frame with two thru bolts. Tighten bolts to 40 - 55 inch lb. torque value.
Bendix Drive Assembly: To inspect and service the Bendix drive, remove starter from engine (remove
two mounting bolts). If drive pinion or splined sleeve is damaged, replace Bendix drive assembly. If
Bendix is in good condition, wipe clean - do not lubricate -- leave completely dry.
Figure 20 Bendix Drive - Ring Gear Engagement
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