Starter Motor Label Activity – Worksheet With a Key

All 15 parts on the diagram

Show the list

The motor 8

Field frame The pole shoes are fixed inside it. The solenoid is mounted on it. It is cut through here, so it shows as a wall all round.
Pole shoes Hold the field coils against the frame. They are the cores the coils magnetize.
Field coils Current through them makes the magnetic field that turns the armature. They are seen cut, one at each end of each pole shoe.
Armature Loops of heavy copper run through its iron core. When current flows in them, the field pushes on them and the armature turns.
Commutator Each bar is joined to an armature coil. As it turns under the brushes, the right coils get current at the right moment.
Brushes They carry the current from the battery into the spinning armature.
Armature shaft The armature and commutator are fixed on it. The clutch and pinion ride on its drive end.
Bushings There is one at each end of the shaft.

Solenoid and drive 7

Solenoid Turning the key sends current to it. Its magnetic pull does two jobs: it moves the pinion into mesh and it switches the motor on.
Plunger The coil pulls it in. Its outer end is pinned to the shift lever.
Contacts A disk is pushed across the two large terminals. That happens when the plunger is pulled right in. Battery current then flows to the motor.
Shift lever It pivots in the middle. When the plunger pulls its top one way, its foot pushes the clutch and pinion the other way, toward the flywheel.
Overrunning clutch It passes the drive one way only. Once the engine fires and runs faster than the starter, it slips, so the engine cannot spin the starter.
Drive pinion Slides along the shaft into mesh with the flywheel's teeth. It cranks the engine.
Flywheel ring gear It is part of the engine, not of the starter. The pinion turns many times for each turn of the flywheel.

How this list was compiled: Part names checked on 2026-09-30; a name is kept only when two independent sources use it. (1) US Army TM 9-8000, Principles of Automotive Vehicles, 1985, chapter 14, Starting Systems, with its figure 14-3, Typical Starting Motor, https://archive.org/details/tm-9-8000-principles-of-automotive-vehicles-1985 (armature, commutator, bronze bushings, field coils, pole shoes, field frame, brushes, armature shaft, pinion, overrunning clutch, solenoid, plunger, shift lever, contact disk and switch contacts, teeth on the rim of the flywheel). (2) W. H. Crouse, Automotive Mechanics, McGraw-Hill 1980, searched in full text at https://archive.org/details/automotivemechan00crou (starting motor: solenoid, plunger, contacts, shift lever, overrunning clutch and drive pinion on the armature shaft, field frame, commutator, brushes, bushings at the drive end and commutator end, flywheel teeth). (3) Wikipedia, Starter (engine), Starter solenoid and Bendix drive, text only (solenoid, a lever that pushes out the drive pinion, starter ring gear on the flywheel, overrunning clutch, armature, field coils, brushes, pole shoes, contacts, plunger). Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; no maker's starter, nothing traced. Licence: own work

How it works

This starter motor label activity has fifteen numbers on two drawings. Numbers 1 to 8 are on the whole starter, cut open along its length. Numbers 9 to 15 are on the solenoid and drive end, drawn larger below it.

Read the full guide

Starter motor diagram labeling worksheet: word bank

Fifteen names, in alphabetical order: armature, armature shaft, brushes, bushings, commutator, contacts, drive pinion, field coils, field frame, flywheel ring gear, overrunning clutch, plunger, pole shoes, shift lever, solenoid.

Numbers that get swapped

Above, the line from 1 ends on the wall of the box (field frame), the line from 2 on the curved block inside it (pole shoes). 4 is the large ribbed drum (armature), 5 the smaller one (commutator), 6 a dark block touching it (brushes). Below, 9 is a long coil in the case (solenoid), 10 the bar sliding out (plunger), 11 the upright plate (contacts). 14 is the small gear (drive pinion), 13 the plain drum behind it (overrunning clutch).

When marking, yoke is right on line 1, shift fork on line 12, one-way clutch on line 13 and pinion gear on line 14.
The top drawing also shows the solenoid, the lever and the small gear. Only the lower drawing numbers them.

Questions and answers

Is a starter motor AC or DC?

DC. The modern starter motor is a direct current motor, either permanent-magnet or series-parallel wound, with a solenoid mounted on it. It runs on power from the starting battery. The one on this sheet is the wound kind, with field coils.

How were cars started before the electric starter?

Commonly by hand, with a removable crank handle that engaged the front of the crankshaft. Hand cranking was inconvenient, difficult and dangerous, because an engine could kick back. During the 1920s electric starters became near-universal on most new cars.

How long can a starter motor run?

Only briefly. A standard starter is designed for intermittent use: its electrical parts are built to work for typically under 30 seconds before overheating, which saves weight and cost.

What is a gear reduction starter?

A starter with a gear train between the motor and the drive shaft. That allows a faster, lighter, more compact motor that draws less current and still cranks with more torque. The starter on this sheet is direct drive, with no reduction gears.