PowerPoint ® Presentation Chapter 4 Small Engine Fundamentals Four-Stroke Cycle Theory Four-Stroke Cycle Engine Operation Engine Components and Functions.

PowerPoint® PresentationPowerPoint® Presentation

Chapter 4Chapter 4Small Engine FundamentalsSmall Engine Fundamentals

Four-Stroke Cycle Theory • Four-Stroke Cycle Engine Operation • Engine Components and

Functions • Small Engine Systems • Compression Systems • Fuel Systems •

Ignition Systems • Lubrication and Cooling Systems • Governor Systems • Electrical

Systems • Braking Systems

Four-Stroke Cycle Theory • Four-Stroke Cycle Engine Operation • Engine Components and

Functions • Small Engine Systems • Compression Systems • Fuel Systems •

Ignition Systems • Lubrication and Cooling Systems • Governor Systems • Electrical

Systems • Braking Systems

Chapter 4 — Small Engine FundamentalsChapter 4 — Small Engine Fundamentals

Gasoline-powered four-stroke cycle engines typically power lawn mowers, snow throwers, lawn and garden tractors, and many other types of outdoor power equipment.

Gasoline-powered four-stroke cycle engines typically power lawn mowers, snow throwers, lawn and garden tractors, and many other types of outdoor power equipment.


Small engines are designed to perform simple tasks with specific types of outdoor power equipment.

Small engines are designed to perform simple tasks with specific types of outdoor power equipment.


A four-stroke cycle engine completes five events in one operating cycle, including intake, compression, ignition, power, and exhaust events.

A four-stroke cycle engine completes five events in one operating cycle, including intake, compression, ignition, power, and exhaust events.


An intake event is an engine operation event in which an air-fuel mixture is introduced to a combustion chamber.

An intake event is an engine operation event in which an air-fuel mixture is introduced to a combustion chamber.


A compression event is an engine operation event in which a trapped mixture of air and fuel is compressed inside the combustion chamber.

A compression event is an engine operation event in which a trapped mixture of air and fuel is compressed inside the combustion chamber.


An ignition event is an engine operation event in which a charge is ignited and rapidly oxidized through a chemical reaction to release heat energy.

An ignition event is an engine operation event in which a charge is ignited and rapidly oxidized through a chemical reaction to release heat energy.


A power event is an engine operation event in which a compressed charge is ignited and hot expanding gases force a piston head away from a cylinder head.

A power event is an engine operation event in which a compressed charge is ignited and hot expanding gases force a piston head away from a cylinder head.


An exhaust event is an engine operation event in which spent gases are removed from the com-bustion chamber and released to the atmosphere.

An exhaust event is an engine operation event in which spent gases are removed from the com-bustion chamber and released to the atmosphere.


Basic small engine components are used for starting, running, and stopping the engine.

Basic small engine components are used for starting, running, and stopping the engine.




Valve location determines whether an engine is an L-head or overhead valve engine.

Valve location determines whether an engine is an L-head or overhead valve engine.


A piston acts as the movable end of the combustion chamber by using the forces and heat created during engine operation.

A piston acts as the movable end of the combustion chamber by using the forces and heat created during engine operation.


Piston rings provide a seal between the piston and the cylinder bore and commonly include a compression ring, wiper ring, and oil control ring.

Piston rings provide a seal between the piston and the cylinder bore and commonly include a compression ring, wiper ring, and oil control ring.


A crankcase houses and supports the crankshaft of an engine.

A crankcase houses and supports the crankshaft of an engine.


A typical small engine fuel system includes a fuel tank, fuel pump (on some models), fuel filter, carburetor, and fuel line.

A typical small engine fuel system includes a fuel tank, fuel pump (on some models), fuel filter, carburetor, and fuel line.


A carburetor provides the required air-fuel mixture to a combustion chamber based on engine operating speed and load.

A carburetor provides the required air-fuel mixture to a combustion chamber based on engine operating speed and load.


A throttle plate is used to regulate the flow of the air-fuel mixture to an engine, while a choke plate is used only to assist in cold starting.

A throttle plate is used to regulate the flow of the air-fuel mixture to an engine, while a choke plate is used only to assist in cold starting.


An ignition system includes multiple magnets, an ignition armature, a spark plug lead, and a spark plug.

An ignition system includes multiple magnets, an ignition armature, a spark plug lead, and a spark plug.


Breaker points control the flow of electricity to other parts of the ignition system circuit.

Breaker points control the flow of electricity to other parts of the ignition system circuit.


A solid-state ignition system has a solid-state transistor in the ignition armature.

A solid-state ignition system has a solid-state transistor in the ignition armature.


The lubrication system and its engine oil absorb heat energy and transfer it to the aluminum cylinder block. The cooling air can then absorb the heat energy from the aluminum and transfer it into the atmosphere.

The lubrication system and its engine oil absorb heat energy and transfer it to the aluminum cylinder block. The cooling air can then absorb the heat energy from the aluminum and transfer it into the atmosphere.


A governor system is an engine system that maintains a desired engine speed regardless of the load applied to the engine.

A governor system is an engine system that maintains a desired engine speed regardless of the load applied to the engine.


A mechanical governor uses the gears and flyweights inside a crankcase as speed-sensing devices to detect changes in a load and adjusts the throttle accordingly.

A mechanical governor uses the gears and flyweights inside a crankcase as speed-sensing devices to detect changes in a load and adjusts the throttle accordingly.


A pneumatic governor uses a movable metal or plastic air vane as a speed-sensing device by registering the change in air pressure around a rotating flywheel.

A pneumatic governor uses a movable metal or plastic air vane as a speed-sensing device by registering the change in air pressure around a rotating flywheel.


A small engine electrical system typically consists of an alternator, rectifier, regulator, and 12 V battery.

A small engine electrical system typically consists of an alternator, rectifier, regulator, and 12 V battery.


An electrical system can be set up to produce either alternating current (AC) or direct current (DC).

An electrical system can be set up to produce either alternating current (AC) or direct current (DC).


Small engine braking systems include several components that are designed to stop an engine quickly.

Small engine braking systems include several components that are designed to stop an engine quickly.