There are many systems for classifying types of motorcycles, describing how the motorcycles are put to use, or the designer's intent, or some combination of the two. Six main categories are widely recognized: cruiser, sport, touring, standard, dual-purpose, and dirt bike. Sometimes sport touring motorcycles are recognized as a seventh category. Strong lines are sometimes drawn between motorcycles and their smaller cousins, mopeds, scooters, and underbones, but other classification schemes include these as types of motorcycles.
There is no universal system for classifying all types of motorcycles. There are strict classification systems enforced by competitive motorcycle sport sanctioning bodies, or by certain legal jurisdictions for motorcycle registration, emissions, road traffic safety rules or motorcyclist licensing. There are also informal classifications or nicknames used by manufacturers, riders, and the motorcycling media. Some experts do not recognize sub-types, like naked bike, that "purport to be classified" outside the six usual classes, because they fit within one of the main types and are recognizable only by cosmetic changes.
The internal combustion engine is an engine in which the combustion of a fuel (normally a fossil fuel) occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine (ICE) the expansion of the high-temperature and high-pressure gases produced by combustion apply direct force to some component of the engine. The force is applied typically to pistons, turbine blades, or a nozzle. This force moves the component over a distance, transforming chemical energy into useful mechanical energy. The first commercially successful internal combustion engine was created by Étienne Lenoir.
The term internal combustion engine usually refers to an engine in which combustion is intermittent, such as the more familiar four-stroke and two-stroke piston engines, along with variants, such as the six-stroke piston engine and the Wankel rotary engine. A second class of internal combustion engines use continuous combustion: gas turbines, jet engines and most rocket engines, each of which are internal combustion engines on the same principle as previously described.
Mechanical engineering is a discipline of engineering that applies the principles of engineering, physics and materials science for analysis, design, manufacturing, and maintenance of mechanical systems. It is the branch of engineering that involves the production and usage of heat and mechanical power for the design, production, and operation of machines and tools. It is one of the oldest and broadest engineering disciplines.
The engineering field requires an understanding of core concepts including mechanics, kinematics, thermodynamics, materials science, structural analysis, and electricity. Mechanical engineers use these core principles along with tools like computer-aided engineering, and product lifecycle management to design and analyze manufacturing plants, industrial equipment and machinery, heating and cooling systems, transport systems, aircraft, watercraft, robotics, medical devices, weapons, and others.
A two-stroke, two-cycle, or two-cycle engine is a type of internal combustion engine which completes a power cycle in only one crankshaft revolution and with two strokes, or up and down movements, of the piston in comparison to a "four-stroke engine", which uses four strokes to do so. This is accomplished by the end of the combustion stroke and the beginning of the compression stroke happening simultaneously and performing the intake and exhaust (or scavenging) functions at the same time.
Two-stroke engines often provide high power-to-weight ratio, usually in a narrow range of rotational speeds called the "power band", and, compared to 4-stroke engines, have a greatly reduced number of moving parts, are more compact and significantly lighter.
The two-stroke power valve system is an improvement to a conventional two-stroke engine that gives a high power output over a wider RPM range.
A stroke is the action of a piston travelling the full length of its cylinder. In a two-stroke engine, one of the two strokes combines the intake stroke and the compression stroke, while the other stroke combines the combustion stroke and the exhaust stroke.
The Honda CR125M Elsinore was a motorcycle designed and manufactured by Honda and released in late 1973. Modeled after the first Elisnore, the Honda CR250M, the 124cc version sold for $749 at its debut. A CR125M ridden by Marty Smith won the 1974 AMA National Motocross championship, echoing the success of Gary Jones on a factory CR250M in 1973 and further spurring the Elsinore's popularity. According to the September 1973 issue of Dirt Bike, the 125 Honda Elsinore was the only off-road bike on the market at the time that offered both speed and reliability. Any other 125cc motocross bike at the time would have to have undergone major suspension, motor, and chassis upgrades to be able to handle the rigors of motocross racing.
The CR125M was built in Japan and was extensively tested on motocross tracks in both Japan and California. It had a chrome-moly tube frame, a six-speed gearbox, four-point adjustable Showa shocks, plastic fenders and a magnesium alloy engine casing for weight economy. The bike weighed 154 pounds dry. With a full tank, the CR125M tipped the scales at 188 pounds. The CR125M’s single-cylinder, two-stroke 124cc engine weighed a scant 46 pounds, inclusive of the 28mm Keihin carburetor.