Motorcycle engine
History
The first motorcycles were powered by steam engines. The earliest example is the French Michaux-Perreaux steam velocipede of 1868. This was followed by the American Roper steam velocipede of 1869, and a number of other steam powered two and three wheelers, manufactured and sold to the public on through the early 20th century.
Using frames based both on the earlier boneshaker and the later—and in many ways completely modern safety bicycle design, these early steam motorcycles experimented with a variety of engine placement strategies, as well as transmission and options. While today nearly every motorcycle has its engine in the center of the frame, this became standard only around 1900-1910[verification needed] after nearly every possible engine location was tried. The modern scooter engine arrangement was arrived at in the 1940s and remains the same today.
The Otto cycle gasoline internal combustion engine was first used on an experimental two wheeler created by Gottlieb Daimler to test the practicality of such an engine in a vehicle. This motorcycle, the Daimler Reitwagen, is credited as the world's first motorcycle by many authorities, partially on the assumption that a motorcycle is defined not as any two wheel motor vehicle, but a two wheel internal combustion engine motor vehicle.The Oxford English Dictionary, for example, defines the word motorcycle this way.The steam cycles were also simply neglected and forgotten by many historians, even as the Michaux-Perreaux waited forty years on display in the National Motor Museum, Beaulieu.
In recent years, a surge in interest in clean energy has put many new electric powered two wheelers on the market, and they are registered as motorcycles or scooters, without the type of powerplant being an issue. Diesel motorcycles were also been experimented with briefly throughout the 20th century, and are again the subject of interest due to fuel economy and the needs of military logistics. The USMC has ordered a new diesel motorcycle, the M1030 M1, that can use the same fuel, JP-8, as the rest of their armored vehicles, aircraft, cars and trucks.
The overwhelming majority of the motorcycles produced and used in the world today have small displacement air-cooled single-cylinder engines, both two- and four-strokes.In the wealthier parts of the world, Europe and Japan, larger displacements and multiple cylinders are common alongside small-displacement bikes required by various licensing and rider experience requirements, and so a very diverse range of sizes, cylinder numbers, configurations, and cooling systems are seen on the road. Many developed countries have graduated licensing, where a rider is licensed for a period of time to ride only smaller-displacement motorcycles before being allowed to ride larger ones. In the United States, there are no such mandates, and so the mix is skewed even further to the largest displacements, consumer demand drives manufacturers to offer their largest motorcycles to that country, and to export far fewer sub-600 cc (37 cu in) models to the American market.
Types
Almost all commercially available motorcycles are driven by conventional gasoline internal combustion engines, increasingly four-strokes in all size ranges. Some are still air-cooled (forced with a fan in some cases) but water-cooling is more common. The mid-range and large two-strokes seen in the 1970s and 1980s have almost disappeared, particularly as emission laws were introduced. There are a few small scooter-type models using batteries and an electric motor. Van Veen, Hercules, Norton, and Suzuki produced quite small numbers of motorcycles propelled by Wankel rotary engines. The 2009 TT races included a new category 'TTX' for electric bikes using either fuel-cells or batteries.
Most motorcycle engines have the primary working member or crankshaft across the frame (transverse mounting). Others are arranged to turn a shaft-drive to the rear wheel and the crankshaft is longitudinal, along the frame.
A sub-type of motorcycle, the scooter, has the engine as part of the rear suspension, so it is not fixed to the main frame. Such engines pivot to follow the road surface and are partly "unsprung weight". The final drive of scooters is much shorter than that of regular motorcycles and is contained within the engine casings in an oil-bath, a design that is only suitable for machines with small wheels, or is fully automatic using belts and expanding/contracting pulleys, ala DAF variomatic cars. The engines of the motorcycles known as underbones or "step-throughs" may be of either kind.
Two-stroke and four-stroke
Two-stroke engines have fewer moving parts than four-stroke engines, and produce twice the number of power strokes; consequently, two-stroke engines are more powerful for their mass. Two-strokes offer stronger acceleration, but similar top speed compared to a four-stroke engine. They are also easier to start. However, two-stroke engines have shorter life due to poorer piston lubrication, since lubrication comes from the fuel-oil mix.
Four-stroke engines are generally associated with a wider power band making for somewhat gentler power delivery, but technology such as reed valves and exhaust power-valve systems has improved ride-ability on two-strokes.[citation needed] Fuel economy is also better in four-strokes due to more complete combustion of the intake charge in four-stroke engines.
Nevertheless, two-strokes have been largely replaced on motorcycles in developed nations due to their environmental disadvantages. Cylinder lubrication is necessarily total-loss and this inevitably leads to a smokey exhaust, particularly on wide throttle openings. Two-stroke engined motorcycles continue to be made in large numbers, but mostly low power mopeds, small scooters and step-through underbones where they still compete strongly with four-strokes (including the highest selling motorcycle of all time, the 50 cc Honda Super Cub). The major markets of two-stroke motorcycles are in developing nations.
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