Adventist Youth Honors Answer Book/Vocational/Small Engines

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Describe the design and operation of the two-cycle engine and the four-cycle engine.

Two-cycle Engine

Four-cycle Engine

Four-cycle engine

A four-cycle engine is so named because it makes four strokes to generate power. These strokes are as follows:

  1. Intake stroke: During this stroke, the piston draws a mixture of fuel and air into the cylinder. The fuel and air enters through an intake valve which opens during this stroke.
  2. Compression stroke: Once the fuel and air have been drawn into the cylinder, the intake valve close and the piston returns towards the engine's head. This compresses the fuel.
  3. Power stroke: When the piston reaches the top of the cylinder, the spark plug fires, igniting the compressed fuel and air mixture and causing an explosion. This explosion causes the gases to expand which powers the piston downwards again. This is where the engines power (and noise!) comes from.
  4. Exhaust stroke: When the piston reaches the bottom of the cylinder, the exhaust valve opens, and as the piston returns to the top of the cylinder again, the exhaust gases are pushed out. When the clylinder reaches the top again, the four cycles are ready to repeat.

Name the parts of the two-cycle engine and tell what each part does.

List four basic fuels used in small engines, and explain their use.

Show care and safety in fuel handling and storage.

Describe three types of ignition systems.

Explain why gasoline is an improper cleaning fluid.

List two acceptable cleaning fluids for small engines.

List and tell how three basic lubrication systems operate.

List in order the steps of a general trouble-shooting procedure.

Demonstrate that you can overhaul, inspect, and properly tune any small engine.

Demonstrate that you know how to test and clean spark plugs and glo plugs.