Small Engine Terminology

This presentation is from Virginia Tech and has not been edited by the Arizona Curriculum Office.

Small Engine Terminology

This presentation is from Virginia Tech and has not been edited by the Arizona Curriculum Office.

Performance Objectives:Performance Objectives:

Students will be able to define, recognize, and utilize terms concerning small engines effectively.

Enabling ObjectivesEnabling Objectives

Students will define small gas engine terms. Students will use correct terminology in

discussion of small engines. Students will recognize small gas engine

terminology and be able to effectively apply terms to usage and maintenance of the engine.

“How does this whachamacallit fit into the whozamathingy?”

“I need a flappy white thing that goes on the top of the engine.”

“ Effectively communicating your intentions is a key point to success. Terminology is the key!”

“How does this whachamacallit fit into the whozamathingy?”

“I need a flappy white thing that goes on the top of the engine.”

“ Effectively communicating your intentions is a key point to success. Terminology is the key!”

Small Engine MaintenanceSmall Engine Maintenance Internal Combustion Engine- Device that burns

fuel inside a cylinder to create a force that drives a piston.

Piston- A sliding cylinder fitting within a cylindrical vessel that receives the force of combusting fuel.

Crankshaft- A shaft with an offset projection that converts circular motion to reciprocal motion, or vice versa.

Reciprocating- return; move back and forth

Horizontal shaft engine- An engine with a crankshaft that lies crossways for normal operation

Vertical shaft engine- an engine whose crankshaft is vertical for normal operation

Stroke- the movement of a piston from top to bottom or from bottom to top

Cycle- All the event that take place as an engine takes in air and fuel, compresses the air fuel mixture, burns the fuel, and expels the burned gasses. Also the current produced by one turn of a generator armature.

Four- stroke cycle- four strokes per cycle Two-stroke cycle- two strokes per cycle Poppet valve- a valve that controls the flow of air

and gasses by moving up and down. Port- a special hole in the cylinder wall of a two cycle

engine to permit gasses to flow in or out of the cylinder.

Reed valve- a flat, flexible plat that permits air or liquid to pass on one direction but seals when the flow reverses.

Intake stroke- engine process of taking fuel and air into the combustion chamber

Compression stroke- Movement of an engine piston to squeeze or compress the air-fuel mixture

Compression ratio- the relationship between the volume of an engine cylinder at the beginning and end of the compression stroke.

Top Dead Center (TDC)- position of a piston when at its highest point (furthest from the crankshaft)

Bottom Dead Center (BDC)- piston at its lowest point ( point nearest the crankshaft)

Fire- flame; to make a spark jump across an air gap

Ignition- a spark igniting an air-fuel mixture Power stroke- the engine process in which

burning fuel expands rapidly but evenly to drive the piston down

Exhaust- burned gasses removed by the motion of a piston

Exhaust Stroke- Movement of a piston which expels burned gases from a cylinder

Revolution- one complete turn of 360 degrees

Momentum- turning force of the flywheel and other moving parts that carries an engine through nonpower strokes.

Maintenance- doing the tasks that keep a machine in good condition

Troubleshooting- determining what causes a malfunction in a machine or process.

Repair- to replace a faulty part or make it work correctly.

Adjust- to set a part or parts to function as designed.

Contaminant- any material that does not belong in a substance

Saturate- to add a substance until the excess starts to run out.

Dual-two Precleaner- a device that removes large

particles from air entering an air cleaner Shroud- to cover; a cover Score- to scratch Torqued- A twisting force; to twist Speed indicator- a device used to measure

revolutions per minute (RPM) of a turning shaft or part.

RPM-revolution per minute

Leaner- a greater proportion of air and lesser proportion of fuel in an air-fuel mixture.

Richer- a mixture with an increased proportion of fuel to air

Labor- to struggle or work hard to keep running

Small Engine Adjustment and RepairSmall Engine Adjustment and Repair Overhaul- complete disassembly with

cleaning and reconditioning or replacement of most moving parts.

Governor- Speed control device Air Vane- type of governor used on small

engines Carburator- Provides fuel and air to the

engine in appropriate portions and volume.

Needle- A long tapered shaft A hole shaped to receive the needle and

control the flow of fuel. Jet or Seat- a hole shaped to receive the

needle and control the flow of fuel. Battery- produces electricity by chemical

action. Magneto- produces electricity by magnetism Condensor- stores and releases current to

boost current in the Primary circuit

Primary circuit- low-voltage circuit of an ignition system

Secondary circuit- high-voltage circuit of an ignition system.

High-tension wire- high voltage wire in a secondary circuit

Electromagnetic induction- conversion of low-voltage current to high-voltage current with a coil.

Ignition spark- hot electrical arc across an air gap

Ignition points- interrupt the flow in the primary circuit at the correct time to induce the high voltage flow to the spark plug.

Discharge- loss of power from a battery Electrolyte- acid solution in a battery Distilled water- free of iron or other parts Armature- the rotating part of a motor. Also

the iron core portion of a magneto. Head gasket- seal between the head and the

cylinder block

Valve Spring Compressor- compresses the valve spring to remove keepers.

Valve keeper- transfers spring force to valve stem

Stem- long, round section of a valve Margin- outer edge of a valve head Face- surface that is intended for use. Also

tapered section of a valve head. Lapped in- grinding valves to fit the seat for

a perfect seal

Lapping compound- gritty material used for lapping in valves

Valve grinding- the process of grinding valves

Valve guide- holds valve stem in alignment Valve stem clearance- air gap between valve

and push rod. Cylinder- engine cavity containing a piston Head- flat part of a valve; cylinder cover

containing the spark plug and combustion chamber.

Piston- a sliding cylinder fitting within a cylindrical vessel that receives the force of combusting fuel.

Rings- complete the seal between the piston and cylinder wall.

Inside micrometer- telescoping gauge used to measure inside surfaces of hollow objects.

Telescoping gauge- inside micrometer Cylinder hone- Tool for restoring cylinders

Ring expander- tool used to remove and install piston rings

Blow-by- compression leakage past pistons Piston ring compressor- used to force piston

rings into their grooves Wrist pin (Crank pin)- pin between a

connecting rod and piston Micrometer- Used to measure outside

surfaces of round objects Plastigage- carefully designed material that

flattens out uniformly when pressed.

Rope starter- rope wrapped around a pulley for turning power to start an engine

Wind up starter- uses a lever to coil a spring for cranking an engine.

Valve pin- Transfers spring force to valve stem

Head- flat part of a valve; cylinder cover containing the spark plug and combustion chamber.

Vocabulary QuizVocabulary Quiz1. Burned gases removed by the motion

of the a piston.2. The movement of a piston from top to

bottom or from bottom to top.3. A sliding cylinder fitting within a

cylindrical vessel that receives the force of combusting fuel.

4. The engine process in which burning fuels expands rapidly but evenly to drive the piston down.

5. Movement of a piston which expels burned gases from a cylinder.

A. Exhaust strokeB. Power StrokeC. PistonD. StrokeE. Exhaust

6. Doing the tasks that keep a machine in good condition.

7. Engine process of taking fuel and air into the combustion chamber

8. Movement of an engine piston to squeeze or compress the air-fuel mixture.

9. A spark igniting an air-fuel mixture10. Turning force of the flywheel and

other moving parts that carries an engine through nonpower strokes.

11. To replace a faulty part or make it work correctly

A. RepairB. MomentumC. Intake strokeD. IgnitionE. Compression

StrokeF. Maintenance

12. Determining what causes a malfunction in a machine or process.

13. All the events that take place as an engine takes in air and fuel, compresses the air-fuel mixture, burns the fuel, and expels the burned gases.

14. Device that burns fuel inside a cylinder to create a force that drives a piston.

15. A shaft with an offset projection that converts circular motion to reciprocal motion, or vice versa.

A. CrankshaftB. TroubleshootingC. CycleD. Internal

Combustion Engine

16. Provides fuel and air to the engine in appropriate portions and volume.

17. Produces electricity by magnetism

18. The rotating part of a motor.19. Seal between the head and the

cylinder block20. Complete the seal between the

piston and the cylinder wall.21. Stores and releases current to

boost current in the Primary circuit.

A. Head gasketB. ArmatureC. CondensorD. MagnetoE. CarburetorF. Rings

21. Used to measure outside surfaces of round objects.

22. Inside Micrometer23. Flat part of the valve24. A twisting force25. Compression leakage past

pistons

A. Telescoping gauge

B. Blow-byC. TorqueD. HeadE. Micrometer