Starter Electric; Purpose; How It Works; Testing - Toro 74161 Service Manual

Purpose

The starter motor pushes the starter pinion into
engagement with the flywheel, then rotates the starter
motor to start the engine.

How It Works

The starter motor is really just a collection of simple
parts:
FIELD: A coil of wire on an iron core that becomes an
electromagnet when current is applied. It surrounds the
armature.
ARMATURE: Eight coils of wire on an iron core that
become electromagnets when current is applied. The
end of each coil is connected to a section of the
commutator. The armature rotates.
COMMUTATOR: The commutator is the connection
point between the brushes and the coils in the
armature. The sections are divided such that only one
armature coil is "on" at a time. This sets the armature to
rotating because the electromagnetic field in the field
coil will oppose the one in the armature.
BRUSHES: Supply power to the commutator.

Testing

With the starter assembled, disconnect the connecting
lead from the starter solenoid C terminal. Connect a
jumper lead from the connecting lead to the battery
positive terminal. Connect a jumper lead momentarily
between the starter motor housing and the battery
negative terminal. If the motor doesn't run, check the
motor for problems.
Mid-Mount Z Service Manual
ELECTRICAL SYSTEMS
Starter
Electric
7 - 25