2 Compression System-Upward movement of piston in the cylinder (compression stroke) compresses the gases into the combustion chamber at the top of piston.-Downward movement of piston (power stroke) turns crankshaft and creates power for engine-Compression is usually lost in 1 of 3 places:- the fit of the piston in the cylinder- a bad head gasket- valves that close improperly
3 Fuel SystemConsists of the fuel tank, fuel lines, carburetor, and intake systemAs piston moves down cylinder on intake stroke, a vacuum is created that pulls through the intake valve and through the carburetorAs air is drawn in, it passes through restrictions in throat of carburetor called venturi and creates a low pressure area that makes air come through more rapidlyValves are opened and closed by a lobed rod called a camshaft. It is timed to open and close valves at a precisely correct time.To prevent the engine from running too fast, a governor is attached to carburetor that slows engine when a certain speed is reached.
4 Ignition SystemWhen fuel mixture has entered the combustion chamber and been compressed, a spark must occur for fuel to igniteMost small gas engines have an ignition system called a magneto in which a spark is created by electrical current generated by process called electrical induction. A low-voltage current is generated when a strong magnet located in flywheel passes very close to armature coil.Spark plug consists of 2 parts:Center electrode that runs length of middle of plugGround electrode that’s grounded to the block of the engine
5 Cooling SystemA small engine can fire and ignite fuel mixture over 2,000 times per minute.Heat generated by combustion can be as much as 3,000 degrees FFins on flywheel serve as a fan to move air across and around engine
6 Lubricating SystemIt’s essential oil is circulated to all internal parts within the crankcase.Oil serves 4 purposes:1.) lubricates moving parts2.) cleans engine3.) movement of liquid oil helps to cool interior of engine4.) oil helps to seal gap between rings and cylinder wall