LessonLesson

Using Small Using Small EnginesEngines

Interest ApproachInterest Approach

How could we accomplish lawn How could we accomplish lawn tasks without small engines?tasks without small engines?

Student Learning ObjectivesStudent Learning Objectives

Identify the reasons why small Identify the reasons why small engines are widely used.engines are widely used.

Describe how small engines can be Describe how small engines can be classified.classified.

Identify common service jobs Identify common service jobs performed on small engines.performed on small engines.

TermsTerms Blow-byBlow-by DegreaserDegreaser Dry-filter type air cleanersDry-filter type air cleaners Horizontal crankshaft engineHorizontal crankshaft engine Oiled-filter type air cleanersOiled-filter type air cleaners Service intervalsService intervals Vertical Crankshaft engineVertical Crankshaft engine

Small enginesSmall engines

25 horsepower or less.25 horsepower or less. Several million are now in use in the Several million are now in use in the

U.S.U.S. Accomplish tasks that other Accomplish tasks that other

equipment cannot do.equipment cannot do.

Small engine popularitySmall engine popularity

CompactCompact LightweightLightweight Easy to service and repairEasy to service and repair AffordableAffordable

Reasons for small engine troubleReasons for small engine trouble

Dirt and dust leads to rapid wear Dirt and dust leads to rapid wear if not serviced properly.if not serviced properly.

Abuse by overloading.Abuse by overloading. Do not receive proper service or Do not receive proper service or

regular maintenance.regular maintenance.

Classifying small enginesClassifying small engines

By the position of their By the position of their crankshafts.crankshafts.

By the number of power strokes By the number of power strokes per crankshaft revolution.per crankshaft revolution.

Position of crankshaftsPosition of crankshafts

Vertical crankshaft engine – its Vertical crankshaft engine – its cylinder is in a horizontal position.cylinder is in a horizontal position.

Horizontal crankshaft engine – may Horizontal crankshaft engine – may have its cylinder in a vertical, have its cylinder in a vertical, horizontal, or intermediate position.horizontal, or intermediate position.

Multi-position crankshaft engine – Multi-position crankshaft engine – operates in any position.operates in any position.

CrankshaftCrankshaftPositionsPositions

Number of power strokesNumber of power strokes

Four stroke cycle engines – Four stroke cycle engines – intake, compression, power, intake, compression, power, exhaust.exhaust.

Two-stroke cycle engines – Two-stroke cycle engines – compression & intake, power & compression & intake, power & exhaust.exhaust.

ExtremeExtremeanglesangles

of of operationoperation

and oiland oilsupplysupply

Service intervalsService intervals

The periods of time between the The periods of time between the performance of service jobs.performance of service jobs.

Common Service JobsCommon Service Jobs

Cleaning the engine.Cleaning the engine. Inspect and clean the exhaust Inspect and clean the exhaust

system.system.Degreaser – solvent good for Degreaser – solvent good for

cleaning hard to reach places.cleaning hard to reach places. Inspect cooling system for Inspect cooling system for

obstructions.obstructions.

Servicing Carburetor Air CleanersServicing Carburetor Air Cleaners

Oil-filter type air cleaner – made Oil-filter type air cleaner – made of a sponge-like filtering material of a sponge-like filtering material called polyurethane.called polyurethane.

Dry-filter type air cleaner – Dry-filter type air cleaner – consists of a porous filtering consists of a porous filtering material made of paper or fiber.material made of paper or fiber.

Types ofTypes ofair air

cleanerscleaners

Lubricating Small EnginesLubricating Small Engines

Engine oil is vital to engine life.Engine oil is vital to engine life. Blow-by – gases under pressure that Blow-by – gases under pressure that

leak by the piston rings during leak by the piston rings during combustion and the power stroke.combustion and the power stroke.

Four cylinder engines are lubricated Four cylinder engines are lubricated from an oil reservoir.from an oil reservoir.

Two-cycle engines are lubricated by Two-cycle engines are lubricated by specific types of oil in the fuel.specific types of oil in the fuel.

Servicing Spark PlugsServicing Spark Plugs

Anything that inhibits the flow of Anything that inhibits the flow of current through the spark plug current through the spark plug and across the spark plug gap and across the spark plug gap will affect the operation of the will affect the operation of the engine.engine.

SparkSparkplugplug

operationoperation

Review/SummaryReview/Summary

Why are small engines so widely Why are small engines so widely used?used?

How are small engines classified?How are small engines classified? What are some of the common What are some of the common

service jobs performed on small service jobs performed on small engines?engines?