1. Engine Construction and Principles of Operation
Chapter 4

2. Objectives Explain simple engine operation.
List the qualities of gasoline that make it an efficient fuel for small engines.
Explain why gasoline is atomized in the small engine.
Identify the basic components of a small engine and describe the function of each part.

3. How does an Engine Work?

4. Gasoline Hydrocarbon fuel (mix of hydrogen and carbon) Gas should
Ignite readily, burn cleanly, resist detonation
Vaporize easily w/o vapor lock
Free of dirt, water, and abrasives

5. Octane Number Ability to resist detonation Low Compression = Regular
High Compression = Premium
Video 1
Video 2

6. Octane Number
Lead
Oxygenates
Ethanol

7. How does gasoline burn?
Liquid?
Vapor?
Atomizing

8. Containing Our Explosion
Minimizing Lost Energy
Combustion Chamber

9. Questions on Page 71

10. Cylinder Block
Keeps all parts aligned
Cast Iron
Aluminum Alloy

12. Cooling Fins
Function
Design

14. Crankshaft Major rotating part of the engine
Forged or Cast Steel with precisely machined and ground bearings

15. Crankshaft Counterweights Crankpin or Connecting Rod Journal Throw
Flywheel
PTO

16. Crankcase Rigid and Strong Keep Parts Aligned
Hold Oil and Keep Out Dirt

17. Piston Straight line driving member of the engine
Subject to direct heat from combustion

19. Piston Adequate clearance to allow for expansion Piston rings
Compression Ring:
Scraper Ring (Compression):
Oil Ring:

20. Piston Ring grooves Characteristics of a Piston
Wrist Pin (Piston Pin):
Retainers

21. Connecting Rod
Connects piston to crankshaft
Bearings
Bearing Cap

22. Intake and Exhaust Ports
Ports (Two Stroke)
Poppet Valves

23. Poppet Valves
Intake (Usually Larger):
Exhaust:

26. Poppet Valves
Valve Face
Valve Seat
Valve Stem

27. Poppet Valves Valve Guide Valve Spring Valve Rotator Retainer (Keeper)
Pin
Collar
Keyhole

28. Valve Lifter or Tappet
Link b/w camshaft lobe and valve stem

29. Camshaft
Timing Gear
Lobe
Compression Release
Position?

30. Flywheel
Three Functions
Momentum
Cooling
Ignition/Accessories

31. Objectives Explain simple engine operation.
List the qualities of gasoline that make it an efficient fuel for small engines.
Explain why gasoline is atomized in the small engine.
Identify the basic components of a small engine and describe the function of each part.