Piper Dakota Maintenance Manual page 537

GENERAL
DESCRIPTION AND OPERATION (figure 80-1)
The gear reduction starting motor comprises commutator end head assembly, armature, frame and field
a s s e m b l y, gear housing, pinion housing, and Bendix drive asembly. When the starting circuit is energ i z e d ,
battery current is applied to the starting motor terminal.
The gear cut on the drive end of the armature shaft extends through the gear housing, where it is supported
by a roller bearing. The gear mates with the teeth of the reduction gear that drives the Bendix shaft. The shaft
is keyed to the reduction gear. The Bendix drive is held in position on the shaft by a spiral pin. The shaft is
supported in the gear housing by a closed end roller bearing and in the pinion housing by a graphitized bronze
bearing.
When the armature turns the reduction gear, the Bendix drive pinion meshes with the flywheel ring gear by
inertia and action of the screw threads within the Bendix sleeve. A detent pin engages in a notch in the screw
threads which prevents demeshing if the engine fails to start when the starting circuit is de-energized.
When the engine reaches a predetermined speed, centrifugal action forces the detent pin out of the notch in
the screw shaft and allows the pinion to demesh from the flywheel.
TROUBLESHOOTING
Troubles peculiar to the starting system are listed in chart 8001 along with their probable causes and
suggested remedies.
PIPER AIRCRAFT
PA-28-236
MAINTENANCE MANUAL
2K21
80 - 02 - 00
Page 80 - 01
Reissued: August 1, 1986