7 Engine ShroudHelps cool the motor by transporting air through the motor like a fan
8 CylinderThe core of the engine is the cylinder. The piston moves up and down inside the cylinder. The engine described here has one cylinder. That is typical of most lawn mowers, but most cars have more than one cylinder (four, six and eight cylinders are common). In a multi-cylinder engine the cylinders usually are arranged in one of three ways: inline, V or flat (also known as horizontally opposed or boxer), as shown in the following figures.
9 Spark PlugThe spark plug supplies the spark that ignites the air/fuel mixture so that combustion can occur. The spark must happen at just the right moment for things to work properly.
10 Cam ShaftThe cam shaft has lobes that open the valves and allow them to close. The cam shaft is driven by the camshaft gear.
11 Carburetor A device that mixes air and fuel for combustion on spark - ignition
12 Connecting RodThe connecting rod connects the piston to the crankshaft. It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates.
13 Crankcase BreatherAllows the air in the crank case to equalize so the pressure remains constant.
14 Crank ShaftThe crank shaft turns the piston's up and down motion into circular motion just like a crank on a jack-in-the-box does.
15 Cylinder HeadAn iron alloy or aluminum casting that bolts on top of the engine block to form the top of the combustion chamber.
16 Air FilterA device that removes dirt and other foreign partials from intake air on an internal combustion engine
17 Oil DipperA device that throws oil around the crank case to lubricate the internal parts of the engine.
18 PistonA piston is a cylindrical piece of metal that moves up and down inside the cylinder.
19 Piston RingsPiston rings provide a sliding seal between the outer edge of the piston and the inner edge of the cylinder. The rings serve two purposes:They prevent the fuel/air mixture and exhaust in the combustion chamber from leaking into the sump during compression and combustion.They keep oil in the sump from leaking into the combustion area, where it would be burned and lost.
20 Starter ClutchHolds the starting rope that starts the motor. Recoils the rope for continuing starting.
21 ValveThe intake and exhaust valves open at the proper time to let in air and fuel and to let out exhaust. Note that both valves are closed during compression and combustion so that the combustion chamber is sealed.
22 Valve SpringThe coil springs that keep the valves closed.
23 Fly WheelA heavy wheel that is part of an internal combustion engine. Attached to the crankshaft, it is used for opposing and moderating by inertia any fluctuation of speed in the rotation of the crankshaft.
27 1st StrokeThe first stroke of the cycle is described as the intake cycle, where the piston that starts at the top of the cylinder chamber, begins to move downward.At the same time that the piston begins it path downward, the intake valve opens and allows air to be drawn into the cylinder chamber by the downward moving piston.Also during this time a small quantity of gasoline is squirted into the chamber through a fuel injector and mixes with the air.
28 2nd StrokeThe second stroke, also known as the compression stroke, begins with the closing of the intake valve. As the intake valve closes a sealed chamber is created between the piston and the top of the cylinder where the valves are located. The piston then begins its upward path, the gasoline and air mixture is compressed at a ratio of roughly 10:1. This ratio comes from the differences in volume between the volume of the cylinder chamber at the top of the pistons stroke compared to the volume of the cylinder chamber when the piston is at the bottom of its path. The greater that this ratio can be made the more power an engine can produce.
29 3rd StrokeThe third stroke of the cycle, the power stroke refers to the combustion itself. Now that the cylinder chamber is full of highly compressed air and gasoline, a spark from a spark plug initiates an explosion in the chamber that causes a rapid expansion of the compressed mixture, resulting in the piston being forced downward very quickly. The expansion of gas, caused by the combustion is the single most important stage of the cycle.
30 4th StrokeThe fourth and final stroke, is known as the exhaust stroke. Once the piston reaches the bottom of its path after the explosion, all that remains in the cylinder chamber is waste.Once the piston begins its movement upward in the cylinder the exhaust valve opens and the piston forces the exhaust out of the chamber and away from the engine. Following this exhaust removal the intake valve opens allowing air to enter the chamber and continue the cycle.