Motorcycle Basics
Motorcycles are motorized vehicles for transporting one or two riders. Generally, a motorcycle has only two wheels, but any vehicle with fewer than four wheels in contact with the ground can be classified as a motorcycle. Three-wheel variations of the motorcycle include the "hack" (motorcycle plus sidecar) and the "trike" (short for motortricycle).
Motorcycles are motorized vehicles for transporting one or two riders. Generally, a motorcycle has only two wheels, but any vehicle with fewer than four wheels in contact with the ground can be classified as a motorcycle. Three-wheel variations of the motorcycle include the "hack" (motorcycle plus sidecar) and the "trike" (short for motortricycle).
The layout of the modern motorcycle was established by 1914 and has
remained fundamentally unchanged ever since. The overall structure and
function of a motorcycle is quite simple. It includes a gasoline engine, which converts the reciprocating motion of pistons into rotary motion, just like the engine in a car. A transmission
system transmits this motion to the back wheel. As the back wheel
turns, it propels the motorcycle forward. Steering is accomplished by
turning the front wheel via the handlebars and by leaning the bike to
one side or the other. Two hand levers enable the rider to operate the
clutch and the front brake, while two foot pedals enable him to change
gears and control the rear brake.
Motorcycle engines work the same way that car engines
do. They consist of pistons, a cylinder block and a head, which
contains the valve train. The pistons move up and down in the cylinder
block, driven by explosions of a fuel-air mixture that has been ignited
by a spark. Valves open and close to allow the fuel-air mixture to enter
the combustion chamber. As the pistons move up and down, they turn a
crankshaft, which transforms the energy from the pistons into rotary
motion. The rotational force of the crankshaft is transmitted, via the transmission, to the rear wheel of the motorcycle.
Motorcycle engines are generally classified by one of three
characteristics: the number of cylinders they possess, the capacity of
their combustion chambers or the number of strokes in their power
cycles.
Cylinders
Motorcycle engines can have between one and six cylinders. For years, the V-twin design was the engine of choice for motorcycle engineers in America, Europe and Japan. The V-twin gets its name from the fact that the two cylinders form a V shape, such as the classic Harley-Davidson V-twin shown below. Notice the 45-degree angle in the Harley-Davidson V-twin -- other manufacturers may vary this angle to reduce vibration.
Motorcycle engines can have between one and six cylinders. For years, the V-twin design was the engine of choice for motorcycle engineers in America, Europe and Japan. The V-twin gets its name from the fact that the two cylinders form a V shape, such as the classic Harley-Davidson V-twin shown below. Notice the 45-degree angle in the Harley-Davidson V-twin -- other manufacturers may vary this angle to reduce vibration.
The V-twin is just one way to accommodate two cylinders. When the
cylinders are oriented so that the pistons oppose each other, the result
is an opposed-twin design. Parallel-twin engines have their pistons
placed side by side in an upright position.
Today, the most popular design is the four-cylinder, which runs more
smoothly and at higher revolutions per minute (rpms) than a comparable
twin. The four cylinders can be placed in a row, or they can be arranged
in a V-shape configuration, with two cylinders on each side of the V.
What's in a name?
The term "biker" has come to be associated with members of motorcycle
gangs, which is why many motorcycle enthusiasts prefer the terms
"rider" or "motorcyclist." Born-again bikers are motorcycle riders in
their 40s and 50s, a demographic that had not been well-represented in
the general population of motorcycle owners until recently.
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Capacity
The size of the combustion chamber in a motorcycle engine is directly related to its power output. The upper limit is about 1500 cubic centimeters (cc), while the lower limit is about 50 cc. The latter engines are usually found on small motorcycles (mopeds) that offer 100-miles-to-the-gallon fuel economy but only reach top speeds of 30 to 35 miles per hour.
The size of the combustion chamber in a motorcycle engine is directly related to its power output. The upper limit is about 1500 cubic centimeters (cc), while the lower limit is about 50 cc. The latter engines are usually found on small motorcycles (mopeds) that offer 100-miles-to-the-gallon fuel economy but only reach top speeds of 30 to 35 miles per hour.
A motorcycle engine can create an enormous amount of power, which
must be delivered to the wheels of the vehicle in a controllable way.
The motorcycle transmission delivers power to the rear wheel through a
series of structures that include the gearset, the clutch and the drive system.
Gearset
A gearset is a set of gears that enable a rider to move from a complete stop to a cruising speed. Transmissions on motorcycles typically have four to six gears, although small bikes may have as few as two. The gears are engaged by shifting a lever, which moves shifting forks inside the transmission.
A gearset is a set of gears that enable a rider to move from a complete stop to a cruising speed. Transmissions on motorcycles typically have four to six gears, although small bikes may have as few as two. The gears are engaged by shifting a lever, which moves shifting forks inside the transmission.
Clutch
The job of a clutch is to engage and disengage power from the engine crankshaft to the transmission. Without the clutch, the only way to stop the wheels from turning would be to turn off the engine -- an impractical solution in any kind of motorized vehicle. The clutch is a series of spring-loaded plates that, when pressed together, connect the transmission to the crankshaft. When a rider wants to shift gears, he uses the clutch to disconnect the transmission from the crankshaft. Once the new gear is selected, he uses the clutch to reestablish the connection.
The job of a clutch is to engage and disengage power from the engine crankshaft to the transmission. Without the clutch, the only way to stop the wheels from turning would be to turn off the engine -- an impractical solution in any kind of motorized vehicle. The clutch is a series of spring-loaded plates that, when pressed together, connect the transmission to the crankshaft. When a rider wants to shift gears, he uses the clutch to disconnect the transmission from the crankshaft. Once the new gear is selected, he uses the clutch to reestablish the connection.
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