MotoGP, the premier class of GP motorcycle racing, has changed dramatically in recent years. From the mid-1970s until 2002 the top class of GP racing allowed 500cc with a maximum of 4 cylinders, regardless of whether the engine was a two-stroke or four-stroke.

Consequently, all machines were two-strokes, due to the greater power output for a given engine capacity. Some two- and three-cylinder two-stroke 500s were seen, but though they had a minimum-weight advantage under the rules, typically attained higher corner speed and could qualify well, they lacked the power of the four-cylinder machines.

In 2002, rule changes were introduced to facilitate the phasing out of the two strokes, probably influenced by what was then seen as a lack of relevance: the last mass-produced 500cc 2-stroke model had not been available to the public for some 15 years. The rules permitted manufacturers to choose between running two-strokes engines (500cc or less) or four-strokes (990cc or less). Manufacturers were also permitted to employ their choice of engine configuration.

Despite the significantly increased costs involved in running the new four-stroke machinery, given their extra 490cc capacity advantage, the four-strokes were soon able to dominate their two-stroke rivals. As a result, by 2003 no two-stroke machines remained in the MotoGP field. The 125cc and 250cc classes still consist exclusively of two-stroke machines. In 2007, the MotoGP class had its maximum engine displacement capacity reduced to 800cc for a minimum of 5 years.

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Tires
Tire selection is critical, usually done by the individual rider based on bike 'feel' during practice, qualifying and the pre-race warm-up laps on the morning of the race, as well as the predicted weather. The typical compromise is between grip and longevity—the softer and 'grippier' the tire, the more quickly it wears out; the harder and less grip, the more likely the tire is to last the entire race. Conserving rubber throughout a race is a specific talent winning riders acquire. Special 'Q' or qualifying tires of extreme softness and grip were typically used during grid-qualifying sessions until their use was discontinued at the end of the 2008 season, but they lasted typically no longer than one or two laps, though they could deliver higher qualifying speeds. In wet conditions, special tires ('wets') with full treads are used, but they suffer extreme wear if the track dries out.

In 2007 new MotoGP regulations limited the number of tires any rider could use over the practice and qualifying period, and the race itself, to a maximum of 31 tires (14 fronts and 17 rears) per rider. This introduced a problem of tire choice vs. weather (among other factors) that challenges riders and teams to optimize their performance on race day. This factor was greeted with varying degrees of enthusiasm by participants. Bridgestone had dominated in 2007 and Michelin riders Valentino Rossi, Nicky Hayden, Dani Pedrosa, and Colin Edwards all acknowledged shortcomings in Michelin's race tires relative to Bridgestone. Rossi, disappointed with and critical of the performance of his Michelin tires, switched to Bridgestones for 2008 and won the World Championship in dominant fashion. Pedrosa switched to Bridgestones during the 2008 season.

In 2008 the rules were amended to allow more tires per race weekend—18 fronts and 22 rears for a total of 40 tires. The lower number of tires per weekend was considered a handicap to Michelin riders. The only MotoGP team using Dunlops in 2007, Yamaha Tech 3, did not use them in 2008 but switched to Michelin.

For 2009, 2010 and 2011, a 'spec' tire supplier, Bridgestone, was appointed by the FIM (Michelin no longer supplying any tires to MotoGP). For the whole season Bridgestone will provide 4 different specifications of front tire, 6 of rear, and a single wet specification—no qualifying specification. For each round, Bridgestone will provide only 2 specifications for front and rear. Tires will be assigned to riders randomly to assure impartiality.


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 2008 series use this solution in either vee 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 (217.037mph), set by Dani Pedrosa 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 (229.8mph) 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 Jerez circuit in 1 minute 40 seconds compared to 1 minute 22 seconds for Formula One.

Engine Specifications

• Configuration: V4 or Inline-4 (MotoGP class), 2-cylinder (250 cc), 1-cylinder (125 cc class)
  
• Displacement: 800 cc (MotoGP class), 250 cc (250 cc class), 125 cc (125 cc class)
  
• Valves: 16-valve (MotoGP), 8-valve (250 cc, 125 cc)
  
• Valvetrain: DOHC, 4-valves per cylinder (MotoGP),
  
• Fuel: Unleaded (no control fuel) 100 Octane
  
• Fuel Delivery: Fuel injection
  
• Aspiration: Naturally-aspirated engine
  
• Power Output: Approximately 220 or 225 hp
  
• Lubrication: Wet sump
  
• Maximum/minimum revs: 17500 - 18000 rpm
  
• Max Speed: 212 MPH
  
• Cooling: Single water pump

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