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Types of Engine


Almost all commercially available motorcycles are driven by conventional gasoline Internal Combustion Engine s, but some small scooter-type models use an Electric Motor

Gasoline engines can be compared by many criteria.


Displacement


Displacement is defined as the total volume of air/fuel mixture an engine can draw in during one complete engine cycle. In a piston engine, this is the volume that is swept as the pistons are moved from top dead center to bottom dead center. To the layperson this is the "size" of the engine. Motorcycle engines range from 50 cc ( Cubic Centimetre s) 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 motorcycles 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 motorcycles are called "twins." A 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). Also popular, especially in Japanese motorcycles, is the Inline Twin This engine configeration was made famous by Edward Turners Triumph Speed Twin,Tiger and of course the Bonniville. In this design the cylinders sit vertically atop the transmission, generally at a close to a 90-degree angle. The Ducati and Moto Guzzi "L-twin" is a V-twin with one cylinder pointing horizontally forward. The cylinders are spaced 90 degrees apart to quell primary vibrations. In comparison Harley-Davidson engines are spaced 45 degrees apart and, due to this setup and their firing order, tend to vibrate more. BMW makes the famous "boxer twin" (or " Flat-twin ") where the cylinders are horizontally opposed, protruding from either side of the frame. The boxer is the only arrangement that is inherently balanced, producing very low vibration levels without the use of counterbalance shafts.

  • Three-cylinder designs are unusual — they are referred to as "triples" and are normally Inline Triples in layout. The British Hinkley built Triumph and Italian Benelli are two of the motorcycle manufactures using triples in their large displacement motorcycles.

  • Four-cylinder engines are colloquially known as "four-bangers." They are quite similar to car engines, and most commonly have a transverse-mounted Inline Four layout, although some are longitudinal (as in the earlier BMW K series). V-4 and Boxer designs (as in the Honda Gold Wing series) have been produced.

  • Six cylinder engines are rare, and found only on the biggest motorcycles. One of the best six cylinder examples is the Kawasaki Z1300.



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 heat sinks (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.They use the 'Otto cycle' Induction-Compression-power-Exaust.In developed countries, two-stroke road-bikes 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


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 previous technology, Magneto s.