Двигатели мотоциклов: история, типы и современные тенденции.

Engine that powers a motorcycle

A motorcycle engine is an engine that powers a motorcycle. Motorcycle engines are typically two stroke or four stroke internal combustion engines, but other engine types, such as Wankels and electric motors, have been used. Although some mopeds, such as the VéloSoleX, had friction drive to the front tire, a motorcycle engine normally drives the rear wheel, power being sent to the driven wheel by belt, chain or shaft. Historically, some 2,000 units of the Megola were produced between 1921 and 1925 with front wheel drive, and the modern Rokon, an all terrain motorcycle with both wheels driven, has been produced since 1960. Most engines have a gearbox with up to six or even 7 ratios. Reverse gear is occasionally found on heavy tourers, for example the Honda GL1600, and sidecar motorcycles, such as the Ural. The rider changes gears on most motorcycles using a foot pedal and manual clutch, but early models had hand levers. More recently, some have automatic or semi automatic gearboxes, and some using CVT transmission. Outside the United States, engine capacities typically ranged from about 50 cc to 650 cc; but in Europe since 1968 motorcycles with larger capacities have become common, ranging as high as the Triumph Rocket 3's engine. In the United States, V twin engined motorcycles with capacities of 850 cc or more have been the norm since the 1920s.

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 after nearly every possible engine location was tried. The origins of the scooter engine arrangement (including the shaft drive) can be traced back to the 19th century but the current layout became generally adopted after the Great War. The modern equivalent became universally popular in the 1950s and remains much the same today. 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 experimented with briefly in 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 models to the American market.

Almost all production motorcycles have gasoline internal combustion engines. Both four stroke and two stroke engines are used, but strict emission laws have led to far fewer two strokes. A few have used Wankel rotary engines, but no Wankel bikes are currently in production. Motorcycle engines can be air cooled or liquid cooled, and optionally include oil cooling as well. Some scooters use batteries and an electric motor. The 2009 TT races introduced a new category 'TTX' (renamed as TT Zero) for electric bikes using fuel cells or batteries. Motorcycle engines can be mounted transversely; with the crankshaft aligned perpendicular to the frame or longitudinally, with the crankshaft parallel to the frame. Motorcycles with transversely mounted engines are more suited to have chain or belt final drive. Motorcycles with longitudinally mounted engines are more suited for shaft final drive. Motor scooters often have the engine as part of the rear suspension, so the engine is not fixed rigidly to the main frame. Instead, the combined engine transmission swingarm assembly is pivoted to follow the road surface and is part of the "unsprung weight". The chain final drive of scooters runs in an oil bath within the engine casings. "Step through" motorcycles may have a rigidly fixed engine, or may have a scooter type arrangement.

Two stroke engines have fewer moving parts than four stroke engines, and produce twice the number of power strokes per revolution. Fuel economy is 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 off road motocross 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 dirt bikes and developing nations.

Cylinder head design has a significant effect on the efficiency of combustion, and hence the power output of the engine. The head may be flat, in which case the combustion chamber resides within the cylinder and/or a depression in the piston crown, but usually a "dome" within the cylinder head provides most of the combustion volume. Motorcycles use poppet valves in a range of designs: side valve, overhead valve (OHV) with pushrod operation, overhead cam (SOHC), and double overhead cam (DOHC). A cylinder with desmodromic valves may have three or even four camshafts. An OHC or DOHC cylinder head will have at least two valves per cylinder (1 inlet and 1 exhaust), but multi valve engines may have three (2 inlet and 1 exhaust), or four (2 inlet and 2 exhaust), or even five (3 inlet and 2 exhaust). Cylinder heads are the hottest part of the engine and require adequate cooling, typically air cooling, oil cooling or liquid cooling. Some motorcycles such as Harley Davidsons, Moto Guzzis and BMWs become identifiable by their cylinder head types, namely airhead, panhead, oilhead, and even knucklehead. The Ducati desmos head enables higher rpm to be achieved without detrimental valve float also known as valve bounce.

In a side valve engine, the valves are operated from the "underhead" cam without special valve gear. Overhead valve (OHV) engines have valves operated by pushrods. Single and double overhead camshaft (SOHC and DOHC, respectively) engines have overhead camshafts typically operated by chain, belt, gear train or bevel gear drive. The earliest motorcycle engines had exhaust valves operated in the same way as a side valve engine, but they had overhead intake valves held closed by a weak spring. The intake valve was opened by the suction caused by the intake stroke. As the need for mechanical control of the intake valve arose, the design was modified by adding another cam to the camshaft and using a pushrod and rocker arm to operate the intake valve. Honda equipped the CBR400F with REV, described as "revolution responding type valve pausing mechanism", in 1983. This system enabled switching over the number of valve operations per cylinder between low and medium speed revolution range and high speed revolution range. In 2002, Honda introduced HYPER VTEC in the VFR800 Interceptor. In 2006, Kawasaki introduced VVT in the Concours 14.

Engines and gearboxes were originally separate items, the gearbox being driven by a "primary chain". Later designs combined the two elements into a single "unit construction". Some manufacturers, such as Norton and Enfield continued with "pre unit" construction until recently, and Harley Davidson still makes pre unit engines today. In the early 1960s, BSA introduced new short stroke unit construction 500 and 650 cc parallel twins to replace their existing pre unit long stroke engines. Triumph modified their large pre unit 500 and 650 cc parallel twins into unit construction engines. The smaller Triumph 350 and 500 cc twins had been unit construction from their introduction in 1957. The decision by Lucas to discontinue making dynamos and magnetos, and to produce only alternators and coil ignition systems, was a significant factor in forcing the redesign. Traditionally, engines and gearboxes had separate lubrication systems with different grades of oil; but modern practice is to use the same oil for both.

Generally, motorcycle engines have between one and six cylinders. The majority of motorcycle engines are configured as singles, parallel twins, triples, fours and sixes; and all these may be inline or transverse. Vee engines include V twins and V fours, and horizontally opposed engines include flat twins, flat fours and flat sixes. Wankel engines are either single rotor or twin rotor. Bigger bikes tend to have more cylinders for smoothness and increased power. Modern singles range in capacity from 50 cc to 660 cc, twins from 175 cc to 1,800 cc, triples from 380 cc to 2,300 cc, and so on.

Single cylinder engines ( "singles" or "thumpers") have the cylinder vertical, inclined or horizontal, the last type most common in step through motorcycles. Single cylinder engines require both a larger flywheel and a heavier duty gearbox than multicylinder engines. Small singles are cheap to build and maintain and are suitable as cheap utility motorcycles. Until the mid 1960s, road racing machines, like the UK's Matchless, AJS and Norton, tended to be large singles, but since then multicylinder racers have become the norm. Off road and smaller dual sport bikes tend to use single cylinder engines. The simplicity of these engines, often relying on a single carburetor, make them relatively easy to maintain and repair in remote locations with few tools. Compared to lightweight off road singles, the modern category of heavier off road adventure bikes tend to forgo such simplicity, and instead have larger and more powerful parallel twin, flat twin, or V twin engines.

Galbusera built a V8 in 1938, and Moto Guzzi experimented over a period of two years with its dual overhead cam 500 cc V8, the Otto Cilindri, in the 1950s. Some custom and one off motorcycles use more than six cylinders. For example, the Boss Hoss motorcycle uses (5,700 cc, 6,000 cc and 8,200 cc) Chevrolet V 8 crate motors. In 2003 Daimler Chrysler manufactured a limited number of Tomahawk concept vehicles with a Dodge Viper V 10 engine. Australian company Drysdale have built short runs of 750 cc V8 superbikes and 1L V8 roadgoing motorcycles, both with engines specifically developed for the purpose. No major motorcycle manufacturer has used eight or more cylinders, although Honda made the 'almost' V8 oval piston NR750 road bike and NR500 GP bike, having eight connecting rods. Morbidelli has shown two V8 prototype road bikes that were not produced.

Liquid cooled motorcycles have a radiator, similar to the radiator on a car, which is the primary way their heat is dispersed. Coolant is constantly circulated between this radiator and the cylinders when the engine is running. While most off road motorcycles have no radiator fan and rely on air flowing over the radiators from the forward motion of the motorcycle, many road motorcycles have a small fan attached to the radiator which is controlled by a thermostat. Some off road motorcycles are liquid cooled, and anti dirt protection is attached to the radiator. The cooling effect of this fan is enough to prevent the engine overheating in most conditions, so liquid cooled bikes are safe to use in a city, where traffic may frequently be at a standstill. Emissions regulations and the market demand for maximum power are driving the motorcycle industry to liquid cooling for most motorcycles. Even Harley Davidson, a strong advocate of air cooled motors, has recently added water cooling to the heads of their V twin motors in their large touring models, with the radiators being hidden in the lower leg fairings. The Harley Davidson Street 500, Street 750, and two V Rod models have 60° V twins that are fully water cooled, as opposed to the traditional air cooled 45° V twins.

Most air cooled motorcycles take advantage of air blowing past the cylinder and cylinder head while in motion to disperse heat. Frequent, sustained stationary periods may cause overheating. Some models, mostly scooters, are equipped with fans that force the air to go past the cylinder block, which solves the problem of city driving. The cylinders on air cooled bikes are designed with fin heat sinks to aid in this process. Air cooled bikes are cheaper, simpler and lighter than their water cooled counterparts.

Some manufacturers use a hybrid cooling method where engine oil is circulated between the engine case and a small radiator. Here the oil doubles as cooling liquid, prompting the name "oil cooling." Suzuki has produced many oil cooled motorcycles. Modern BMW R series flat twin motorcycles, such as the R1150GS, use air and oil cooling. Polaris's Victory motorcycles use oil/air cooling exclusively.

Fuel injection and computer engine management systems are now normal on middle range and larger motorcycles and are increasingly being incorporated onto the smaller machines, partly driven by better emission control and lower maintenance but mostly by manufacturing cost considerations.

Ignition systems moved from magneto in the 1950s to battery coil contact breaker points, and these were increasingly superseded by Capacitor Discharge Ignition (CDI) from the 1980s. Small, single cylinder motorcycles abandoned the flywheel magneto system with contact breakers to similar flywheel driven solid state systems at about the same time.

Superchargers, or blowers, were common in the GPs, until they were banned. The first supercharger on a production motorcycle was the 2015 Kawasaki Ninja H2 and H2R. The big four made a turbocharged bike, and Honda made two, mainly as an exercise in technical expertise and later discontinued them for more conventional methods. Bolt on superchargers are available for street bikes and are essential for performance applications such as drag bikes and land speed record streamliners. Most sports bikes now use a ram air induction system where as road speed increases, more air is forced through ducts in the fairing to pressurize the airbox. The first on a production motorcycle was the 1990 Kawasaki Ninja ZX 11. Not to be confused with the original Ram Air system where an air scoop/cowl was fitted to the top of the cylinder heads of Suzuki two stroke engines to aid cooling.