Grand Prix class

125cc and 250cc classes
125cc KTM Grand Prix motorcycle

125cc machines are restricted to a single cylinder and a minimum weight of 80 kilograms and the 250cc machines to two cylinders and a minimum of 100 kilograms. From 2005 onwards, all riders in the 125cc class could not be older than 28 years or 25 years for new contracted riders participating for the first time and wild-cards.

In 2008 discussions arose surrounding the replacement of the 2-stroke 250cc class with another category. The move to 600cc 4-stroke engines to replace the current 250s has been finalized as of June 2008 and will take effect in 2011 [7] The new class will be called Moto2. Engines will be produced by Honda[8]; tyres by Dunlop and electronics will be limited and supplied only by FIM sanctioned producers with max cost set at 650 EUR; carbon-fibre brakes will be banned and only steel brakes will be allowed. However, there will be no chassis limitations.[9]
[edit] MotoGP class

New specifications for each racing class are formed as the FIM sees fit. At the beginning of the new MotoGP era in 2002, 500cc two-stroke or 990cc four-stroke bikes were specified to race. The enormous power advantage of the larger displacement four-stroke engine over the two-stroke eliminated all two-strokes from competition; the following season no two-stroke bikes were racing. In 2007 the maximum engine capacity was reduced to 800cc without reducing the existing weight restrictions.

MotoGP-class motorcycles are not restricted to any specific engine configuration. However the number of cylinders employed in the engine determines the motorcycle's permitted minimum weight; more cylinders attracting more weight as a form of handicap. This is necessary because, for a given capacity, an engine with more cylinders is capable of producing more power. If comparable bore to stroke ratios are employed, an engine with more cylinders will have a greater piston area and a shorter stroke. The increased piston area permits an increase in the total valve area, allowing more air and fuel to be drawn into the engine, and the shorter stroke permits higher revs at the same piston speed, allowing the engine to pump still more air and fuel with the potential to produce more power but with more fuel consumption too. In 2004 motorcycles were entered with three-, four-and five-cylinder configurations. A six-cylinder engine was proposed by Blata, but did not reach the MotoGP grids. Presently four cylinder engines appear to offer the best compromise between weight, power and fuel consumption as all competitors in the 2009 series use this solution in either 'V' or in-line configuration.

In 2002, the FIM become concerned at the advances in design and engineering that resulted in higher speeds around the race track. For purposes of increasing safety, regulation changes related to weight, amount of available fuel and engine capacity were introduced. The amended rules reduced engine capacity to 800cc from 990cc and restricted the amount of available fuel for race distance from 26 litres in year 2004 to 21 litres in year 2007 and onwards. In addition, the minimum weight of 4 cylinder bike used by all participating teams was increased by 3 kg.

The highest speed for a MotoGP motorcycle is 349.288kph (217.037 mph), set by Dani Pedrosa riding a Repsol Honda RC212V 800cc during Free Practice 1 at the 2009 Italian motorcycle Grand Prix.[10] By way of comparison, the current Formula One speed record of 369.9kmh (229.8 mph) was set by Antônio Pizzonia of the BMW Williams F1 team, at Monza in 2004—however, top speed is only a small portion of the overall capabilities of any track vehicle and thus does not represent the difference between Formula One and MotoGP performance-wise in general. Using lap timings as a guide, MotoGP riders typically lap the Spanish Circuit de Catalunya in 1 minute 43 seconds compared to 1 minute 23 seconds for Formula One. Generally, cars have more grip thanks to more tires with bigger surface contact area which results in greater corner speed. Bikes have better acceleration regarding to better power to weight ratio. Both of these "rules" apply when comparing an F1 car with a MotoGP bike.
[edit] Weights
Minimum Weight - MotoGP Class Number of
cylinders 2002 Minimum 2007 Minimum Difference
2 135 kg (300 lb) 137 kg (300 lb) 2 kg (4.4 lb)
3 135 kg (300 lb) 140.5 kg (310 lb) 5.5 kg (12 lb)
4 145 kg (320 lb) 148 kg (330 lb) 3 kg (6.6 lb)
5 145 kg (320 lb) 155.5 kg (343 lb) 10.5 kg (23 lb)
6 155 kg (340 lb) 163 kg (360 lb) 8 kg (18 lb)

* In 2005, fuel tank capacity was reduced by 2 litres to 24 litres
* In 2006, fuel tank capacity was reduced by a further 2 litres to 22 litres
* From 2007 onwards and for a minimum period of five years, FIM has regulated in MotoGP class that two-stroke bikes will no longer be allowed, and engines will be limited to 800cc four-strokes. The maximum fuel capacity will be 21 litres.