Small Engines Chapter 4

Cooling

Heat dissipation

One end of the connecting rod is fastened to the piston. The other end is fastened to an offset ______, or _____ of the crankshaft.

Crankpin / Journal

The _____________ is the major rotating part of the engine.

Crankshaft

The __________ keeps all other parts of the engine in proper alignment.

Cylinder Block

The flywheel end of the crankshaft is ________ to fit the hole in the flywheel.

Designed

Mechanical Engine Operation

Engine design and construction

Burned gases are released through a(n) _____ _______ following the power stroke of the piston.

Exhaust Port

Both valves are closed during the period of the ________.

Expansion of burning gases

Ignition

Firing the fuel charge

Expanding __________ push the piston toward the crankshaft, causing the connecting rod to turn the shaft.

Gases

Explain why we should conserve gasoline and use it wisely.

Gasoline cannot be recycled

Crankshafts for small engines are generally made from ________ steel

Hardened (alloy)

The force applied to the piston is a result of the________________________________________________________________________________

Heated gases applying pressure to the top of the piston and cylinder walls.

What is the purpose of the spring keeper and washer?

Helps maintain the engine so that it does not blow up/combust.

An engine with a relatively high compression should use gasoline that has a ______ _________ _______ ________ _______.

High octane and burns slow.

To reduce vibration during operation, the crankshaft has _________ to equal the weight of the _________ __________.

Holes / Connecting Rod

Gasoline is a petroleum product that is mainly a mixture of ______ and _______.

Hydrogen / Carbon

The piston provides a(n) _________ between the combustion chamber and the crankcase.

Seal

Why are aluminum cylinder blocks cast around a steel sleeve?

The aluminum would ware out quickly due to friction with the piston.

During assembly, _______ __________ on the camshaft gear and crankshaft gear must be matched.

Timing marks

What is the purpose of the camshaft?

To cooperate with the crankshaft in order to maintain air/fuel levels within the engine.

The camshaft timing gear is always __________ as the camshaft gear.

Twice as large

How are valves kept in alignment?

Valve guides help align the valves

In order to expose more surface area of the fuel to create rapid burning, the fuel is broke into very small droplets and mixed with air. This process is called ______________.

Atomizing

Carbonation

Atomizing gas and adding it to the cylinder

A gasoline engine is a mechanism that transforms _______ energy into ________ energy for doing useful work.

Chemical / Mechanical

A gasoline engine is an internal ________ engine.

Combustion

The space above the piston where the combustible mixture burns is called the _________ chamber.

Combustion

The sliding piston is connected to the rotating crankshaft with a metal link called a(n) _____________.

Connecting Rod

To perform useful work, the explosive force caused by burning gas must be __________ and ____________.

Contained / Controlled

Cooling efficiency of air-cooled engines is improved through the use of ______ ______.

Cooling fins

In an internal combustion engine, the gasoline is combined with _______ and burned inside the engine.

Air

Cylinder blocks for small engines are usually made of _______ or a(n) _____________ alloy.

Aluminum / Iron

As burned gases are released, a fresh _______-_______ charge enters the cylinder, and the momentum of the power stroke turns the crankshaft journal through bottom dead center (BDC)

Air-fuel

List three desirable characteristics of gasoline for use in engines.

1. Ignites readily 2. Free of dirt, water, and abrasives 3. Resists detonation

What three things do piston rings do?

1. Prevent blow-by of exhaust gases into crankcase 2. Prevent leakage of oil into combustion chamber 3. Fit the grooves near top of piston with a slight side clearance

List three functions of the flywheel

1. Store rotational energy 2. Provides mounting engine output 3. Means of rotating engine by cranking the motor during startup.

Why is a woodruff key used to prevent the flywheel from turning on the crankshaft?

It cannot slip out during operation

__________ and __________ are used to prevent oil leakage from the crankcase.

Lockwasher / Nut

What do valve lifters do?

Maintain zero valve clearance in an internal combustion engine.

Lubrication

Oiling of moving parts

The ___________ is the straight line driving member of the engine.

Piston

Intake and exhaust ports are sealed with ___________ valves.

Poppet

The cylinder block must be rigid and strong enough to contain the ________ developed by the expanding gases.

Power

The crankcase must be rigid and strong enough to withstand the ________ forces of the crankshaft, while keeping all parts in proper alignment.

Rotational

The piston is hollow to reduce__________.

Weight