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