Motorcycle Engine
From Freepedia
A motorcycle engine is, unsurprisingly, an engine found in a motorcycle, which serves to propel the motorcycle. The motor typically sits immediately under the fuel tank, between the rider's legs.
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Types of Engine
Image:Motorcycle engine configs.PNG
Almost all commercially available motorcycles are driven by conventional gasoline internal combustion engines, but some small scooter-type models use an electric motor, and a very small number of diesel models exist (e.g., the USMC M1030 M1). Talk show celebrity Jay Leno owns a motorcycle that is powered by a turboshaft engine.
Gasoline engines can be compared by many criteria.
Displacement
Displacement refers to the total volume of empty space in the combustion chamber(s) if the piston(s) were all fully retracted. To the layperson this is the "size" of the engine. Motorcycle engines range from 50 cc (cubic centimetres) to 2300 cc.
Number of cylinders
Motorcycles have mostly, but not exclusively, been produced with one to four cylinders, and designers have tried every imaginable layout. Engines with more cylinders provide more power for the same displacement, and feel smoother to ride. Engines with fewer cylinders are cheaper, lighter and easier to maintain.
- One-cylinder bikes are known as "singles," and "thumpers" (for the sound they make). In most singles, the cylinder points up and slightly forward, spark plug on top.
- Two-cylinder bikes are called "twins." The most common arrangement is a "V-twin" where the cylinders form a "V" around the crankshaft, which is oriented transversely (i.e., perpendicular to the direction of travel). Typically, the angle of the V is 90°. The Ducati "L-twin" is a V-twin with one cylinder pointing horizontally forward. Also common is the "parallel twin," where, as the name suggests, the cylinders are parallel. BMW makes the famous "boxer twin" (or "flat-twin") where the cylinders are horizontally opposed, protruding from either side of the frame.
- Three-cylinder designs are unusual — they are referred to as "triples" and usually laid out in parallel. The British Triumph and Italian Benelli are two of the motorcycle manufactures using triples in their large displacement motorcycles.
- Four-cylinder engines are known as "four-bangers." They are quite similar to car engines, and most commonly laid out in parallel, although "V" and square designs have been produced.
- Six and eight-cylinder engines are rare, and found only on the biggest bikes. There is even a ten-cylinder concept-bike called the Tomahawk created by Dodge. It uses the same engine found in their Viper model car.
Cooling: Water or Air
Water-cooled motorcycles have a radiator (exactly like the radiator on a car) which is the primary way their heat is dispersed. Water is constantly circulated between this radiator and the cylinder when the engine is running. The radiator has a small fan attached to it which is controlled by a thermostat. The cooling effect of this fan is enough to prevent the engine overheating in most conditions, thus water-cooled bikes are safe to use in a city, where traffic may frequently be at a standstill.
Air-cooled motorcycles have no "cooling system," as such. As air blows past the engine case, it disperses heat. The cylinders on these bikes are designed with fins to aid in this process. Air cooled bikes are cheaper, simpler and lighter than their water-cooled counterparts, but unless the ambient temperature is cold, they will overheat quickly if the bike stands still, as in traffic. 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, hence the name "oil-cooling."
Four stroke or Two stroke
As applied to motorcycles, two stroke engines have some advantages over equivalent four-strokes: they are lighter, mechanically much simpler, and produce more power when operating at their best. But four-strokes are cleaner, more reliable, and deliver power over a much broader range of engine speeds. In developed countries, two-stroke road-bikes above 50 cc are rare, because - in addition to the reasons above - modifying them to meet contemporary emissions standards is prohibitively expensive. Almost all modern two-strokes are single-cylinder, air-cooled, and under 600 cc.
Other components
Motorcycle engine technology generally lags behind that of car engines. Fuel injection and computer engine management systems are now usual on large and expensive bikes, and starting to propagate to smaller bikes, driven by increased demands for emission control and improved performance. Capacitor Discharge Ignition (CDI) is now standard on all bikes, as opposed to the magnetos of yesteryear. More expensive designs now use nikasil as the cylinder coating, leading to much improved engine life.
