ATV Maintenance & Service Manual 1974-1987 Vol. 1 - Honda, Kawasaki, Polaris, Suzuki, Yamaha

OPERATING PRINCIPLES

ENGINE TYPES

The engines used to power all-terrain vehicles and many other items of power equipment in use today are basically similar. All are technically known as "Internal Combustion Reciprocating Engines."

The source of power is heat formed by the burning of a combustible mixture, usually petroleum products and air. In a reciprocating engine, this burning takes place in a closed cylinder containing a piston.

Expansion resulting from the heat of combustion applies pressure on the piston to turn a shaft by means of a crank and connecting rod.

The fuel-air mixture may be ignited by means of an electric spark (Otto Cycle Engine) or by heat formed from compression of air in the engine cylinder (Diesel Cycle Engine).

The complete series of events which must take place in order for the engine to run may occur in one revolution of the crankshaft (two strokes of the piston in cylinder) which is referred to as a "Two-Stroke Cycle Engine," or in two revolutions of the crankshaft (four strokes of the piston in cylinder) which is referred to as a "Four-Stroke Cycle Engine."

OTTO CYCLE: In a spark ignited engine, a series of five events is required in order for the engine to provide power. This series of events is called the "Cycle" (or "Work Cycle") and is repeated in each cylinder of the engine as long as work is being done. This series of events which comprise the "Cycle" is as follows:

1. The mixture of fuel and air is pushed into the cylinder by atmospheric pressure when the pressure within the engine cylinder is reduced by the piston moving downward in the cylinder (or by applying pressure to the fuel-air mixture as by crankcase compression in the crankcase of a "Two-Stroke Cycle Engine" which is described in a later paragraph.



2. The mixture of fuel and air is compressed by the piston moving upward in the cylinder.



3. The compressed fuel-air mixture is ignited by a timed electric spark.



4. The burning fuel-air mixture expands forcing the piston downward in the cylinder thus converting the chemical energy generated by combustion into mechanical power.



5. The gaseous products formed by the burned fuel-air mixture are exhausted from the cylinder so that a new "Cycle" can begin.

The above described five events which comprise the work cycle of an engine are commonly referred to as:

1. INTAKE



2. COMPRESSION



3. IGNITION



4. EXPANSION (POWER)



5. EXHAUST

ENGINE FUNDAMENTALS
Operating principles | Carburetion | Ignition system

SERVICE FUNDAMENTALS
Troubleshooting | Maintenance: spark plug, carburetor | Ignition | 4-stroke valve system | Lubrication | Clutch control | Mixing gasoline and oil—2-stroke engines

METRIC CONVERSION CHARTS

MAINTENANCE LOGS