The Ultimate Repairing a Small Engine Quiz

Combustion and friction produce heat that can damage the engine parts. To prevent this, air is used to cool the engine and lubricant is used to reduce the amount of friction - smaller engines generally don't have liquid coolant systems.

It's best and safer to disconnect the spark plugs before working on an engine. Internal combustion can't start without a spark, so removing the spark plug makes sure you don't get any surprises when you get to work.

A little corrosion on your battery's terminals is normal, but they should be cleaned off so the battery terminals are making good contact. Battery cables and terminals should be cleaned with a little baking soda and a stiff wire brush.

Viscosity is the thickness of an oil, grease or other lubricant. Different grades of oils are designed to work optimally in various temperatures.

Wear parts, such as bearings, wear out as part of their function and are designed to be replaceable. Your engine will generally let you know, through noises or decreased functionality, when parts such as these need to be replaced.

If you have trouble with a repair, many equipment manufacturers can provide copies of their products' repair manuals. Even more helpfully, many of these manuals are available online in PDF format on the manufacturer's website.

White or blue exhaust is a sign that the engine is burning oil. This could be due to overfilling the crankcase with oil, operating the engine at an extreme angle or using an incorrect oil grade, or something more series, like a blown head gasket or worn cylinders.

Magneto-powered and battery-powered are both examples of ignition systems commonly used in small engines. A magneto is a type of electrical generator that has been designed to make high-voltage pulses that supply power to the spark plug.

A governor maintains the speed of the engine, keeping it constant whether it is undergoing a light or heavy load at any given moment. A mechanical governor uses a system of flyweights and springs to measure the load on an engine; an air vane governor uses changes in air pressure around the rotating flywheel to determine the load.

A choke is a valve that controls the air entering the engine and used in the air/fuel mixture. When starting a small engine, the choke restricts the amount of air to run a more fuel-rich mixture until the engine warms up. Once at operating temperature, turn the choke off and allow more air in for a more-balanced mix.

Fuel stabilizer should be added to the fuel when a vehicle or piece of equipment is being stored. If the water content of gasoline is allowed to evaporate, the remaining fuel can form a resin that can damage an engine. Stabilizer helps to prevent this process.

Untreated gasoline breaks down with exposure to oxygen but should last between three and six months if stored in a tightly sealed plastic container or metal tank. Gasoline that has been fuel stabilized can be kept between one and three years.

Gasoline is a highly combustible liquid but still needs oxygen to make it burn. This combustion occurs in the cylinder and moves the piston to turn this explosion into mechanical force. In a two-stroke engine, oil is mixed with the fuel to help lubricate the crankcase. The four-stroke engine is structured differently and doesn't need this fuel/oil mix.

The throttle controls the speed of the engine by controlling the amount of air that is delivered to the engine which affects how much fuel is delivered - the correct proportion determined by the carburetor - and therefore controls the engine's speed.

By pulling the cord, you're actually rotating the crankshaft which is connected to the magneto. The magneto generates the electrical charge that ignites the internal combustion process, which then keeps the crankshaft rotating and the process moving along.

The flywheel - a round-shaped, weighted wheel - maintains the momentum between the engine's power (combustion) strokes. The crankshaft is moved by the piston's up-and-down motion in the cylinder via the connecting rods, but since there is a moment between combustion strokes, the flywheel keeps the crankshaft in motion.

You should change your engine oil in your lawnmower after every 25 to 50 hours of use. Most small engines come with a service chart which helps you keep track of which parts need to be serviced when.

In-line fuel filters are usually made of disposable pleated paper, which should be replaced when cleaning the fuel system. Other engines have a fuel strainer in the bottom of the fuel tank, or a removable sediment bowl type strainer in the fuel line.

Air cleaners keep particles in the air from blocking the carburetor. There are two types: oil baths, which can be cleaned (but are messy to work with) and dry cleaners, which must be replaced.

There are three types of carburetors that are usually used in small engines: natural draft (or side draft), downdraft and updraft. These describe the direction of air flow from the inlet to the engine.

An internal combustion, gasoline-powered engine has six basic systems: fuel, exhaust, ignition, combustion, cooling and lubrication. Each of these systems, of course, has many components.

An incorrectly adjusted governor will damage or destroy an engine by causing it to operate at excessively high speeds. All governors operate differently, so read your service manual to see how to correctly adjust yours.

In a battery cell, the electrolyte material provides a medium of transporting the ions between the lead plates that generate electricity.

A new spark plug requires 5,000 volts to work. An old spark plug can require double as much, so it's important to change out the plug on a regular basis.

Two-stroke engines are lubricated by mixing oil and gasoline. You can buy a premixed product, or mix it yourself using a vented gas canister that is set aside for mixing only.

Some engines require that their parts be lubricated using lubrication grease, a high-viscosity petroleum product. Most lubricating greases have a viscosity of between 80 and 90. Check your owner's manual for recommendations and which parts, if any, require lubrication grease.

Because it's a machine built around a series of explosions, heat quickly becomes an issue. An internal combustion engine reaches about 4,500 degrees Fahrenheit (2,500 degrees Celsius). Therefore, an engine's cooling system is an essential component of its functioning.

Most single-cylinder engines are cooled by air that is generated by fan blades on a flywheel. This system is easy to service; it just needs to be cleaned and kept free of debris.

Many problems can cause an engine to overheat, such as a gasket that needs to be replaced. Other causes might be low oil levels, dirt and debris clogging the air filter or damaged cooling fins.