New Holland WorkMaster 50 Service Manual page 671

Starter solenoid
The starter solenoid is an electromagnetic type solenoid
that is located on the bottom of the starter motor assem-
bly. The solenoid contains two coils, a pull-in coil, (1)
and a hold-in coil (2) When the key switch is turned to
the "START" position and the safety start relay is closed
(safety switches closed), current from the battery will en-
ergize the solenoid's two coils. With the coils energized,
the solenoid plunger, (3) pushes a spring (4) which will
then push the pinion gear out to engage the flywheel. At
the same time, a set of contacts (5), on the solenoid be-
come closed, allowing current to flow to the starter motor.
Closing the contacts also supplies current to both ends
of the solenoid pull in coil which makes the coil become
non-energized. The hold-in coil continues to engage the
pinion gear with the flywheel.
Pinion clutch
To prevent the engine from driving the starter motor once
the engine is running, the pinion gear is equipped with an
overrunning clutch. The clutch will disengage the pinion
gear from the rest of the starter components once the en-
gine has been started and the key switch is in the "START"
position. The clutch consists of an outer gear/shell, (1), a
cam with tapered notches, (2), rollers, (3), roller springs,
(4), a splined pinion collar/tube that acts as a clutch hub,
(5), and the pinion shaft, (6). As the starter motor engages
and rotates, the rollers are locked against the pinion collar
with the tension provided by the roller springs. While the
rollers are locked, the clutch assembly is locked, allowing
the pinion gear to rotate the flywheel. When the engine
starts, the flywheel moves faster than the starter motor
and this causes the rollers to become unlocked. With the
rollers unlocked, the clutch assembly is unlocked, allow-
ing the pinion gear and shaft to turn independently of the
starter motor.
The clutch is not serviceable and is replaced as a com-
plete assembly.
Once the engine is started and the key switch is released
from the "START" position, the solenoid's pull in coil be-
comes energized, pulling the solenoid plunger in, which
disengages the pinion from the flywheel.
Electrical systems - Engine starting system
A -
(1) Clutch Gear
(2) Cam
(3) Roller
(4) Spline Tube - Inner (Pinion Collar)
(5) Pinion Shaft
(6) Roller Spring
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55.5 [55.201] / 4
SEC55CH4PG29_1
SEC55CH4P29_2
Engaged, B - Disengaged
SEC55CH4P29_3
2
3
4