THE MOTO GP ENGINE DEFINITION

2-stroke and 4-stroke – 2-stroke engines were predominant in the World Championship until the switch to the 990cc 4-stroke class in 2002, reflecting production trends, as 2-stroke bikes became increasingly popular from the 1960s through to the 1990s.



If 2-stroke engines proved more powerful than 4-strokes with similar engine capacities and similar rev counts, 4-strokes engines are more energy efficient and greener. This is because 4-strokes have a dedicated lubrication system, while 2-stroke engines burn a mixture of oil and gas.
As most manufacturers shifted their production towards bigger 4-stroke powered machines, the move to a 4-stroke prototype formula only seemed natural.
The key difference between the two types of engine lies in the combustion process: the four ‘strokes’ refer to the intake, compression, combustion and exhaust movements which occur during two crankshaft rotations per working cycle.
The 2-stroke internal combustion engine differs from the 4-stroke engine in that it completes the same four processes in only two strokes of the piston.
Single cylinder, two cylinder, four cylinder and six cylinder engines – While technical rules restrict the 125cc World Championship to single cylinder engines and Moto2 to the Official Engine, MotoGP bikes can have from one cylinder to six cylinders or more.
According to the FIM rulebook, the number of cylinders from one to six, or more, dictate what the minimum accepted weight of the bike will be, as ballast may be added to achieve it. Due to unit cylinder performance and power-to-weight ratio, all the MotoGP manufacturers now use four cylinder engines.
However, those engines come in different forms, as some factories, such as Ducati, Honda and Suzuki currently opt for V4 architecture, while Yamaha and Kawasaki have developed ‘inline four’ engines.
With V4’s the cylinders and pistons are aligned separately to each other, so that they take on a ‘V-shape’ from an angle looking along the crankshaft axis. This configuration decreases the total height, length and weight of the engine, in comparison with straight engine inline equivalents.
The choice of engine architecture has as much to do with design philosophy and the manufacturer’s heritage as with weight transfer and goals in terms of bike ‘rideability’.
Meanwhile, the terms 125cc, 600cc (Moto2), 800cc (MotoGP) used to describe the three current categories in the World Championship simply refer to the ‘engine displacement’ or ‘cubic capacity’ of the respective machinery.

source:www.motogp.com
www.en.wikipedia.org