Here are the rules:
2. TECHNICAL REGULATIONS
2.1.1 The FIM Road Racing World Championship Grand Prix is for
motorcycles, i.e. vehicles with two wheels that make one track
propelled by an internal combustion engine, controlled exclusively by
2.1.2 Providing that the following FIM Road Racing World Championship
Grand Prix regulations are complied with, the constructors are free to
be innovative with regard to design, materials and overall construction
of the motorcycle.
2.2.1 The following classes will be accommodated, which will be designated
by engine capacity :
125 Over 80cc up to 125cc – Maximum one cylinder
250 Over 175cc up to 250cc – Maximum two cylinders
500 Over 350cc up to 500cc – Maximum four cylinders
4-stroke prototype motorcycles : Over 350cc up to 990cc
A four stroke prototype motorcycle must have an engine of original
design and must not use castings of the crankcase, cylinder or
cylinder head derived from the industrial production. The moving parts
(crankshaft, pistons, connecting rods, gearbox etc.) are not taken into
An FIM homologated motorcycle as Superbike or Supersport cannot
be modified for use in the Grand Prix until 2004. Then this rule will be
amended in accordance with a new decision to be taken by the Grand
To be eligible for an FIM homologation the motorcycle can only be
presented by the original manufacturer who must have built a
minimum quantity of units.
2.3.1 Engines may operate on the two stroke or four stroke principal only.
2.3.2 Engines must be normally aspirated.
2.3.3 Cubic capacity of the engine will be defined by the swept volume of
the cylinder, i.e. the area of the bore of the cylinder multiplied by the
2.3.4 No tolerance on capacities is permitted.
2.3.5 Engine capacity must be measured at ambient temperature.
2.4.1 There must be a maximum of six gears.
2.5.1 The following are the minimum weights permitted :
– 125cc motorcycle + rider 136 kg
– 250cc 1 cylinder motorcycle 100 kg
2 cylinders motorcycle 100 kg
– 500cc 1 cylinder motorcycle 101 kg
2 cylinders motorcycle 101 kg
3 cylinders motorcycle 116 kg
4 cylinders motorcycle 131 kg
– 4-stroke prototype motorcycles :
• 3 cylinders or less 135 kg
• 3 cylinders or less with oval piston 145 kg
• 4 and 5 cylinders 145 kg
• 4 cylinders or more with oval piston 155 kg
• 6 cylinders or more 155 kg
2.5.2 Ballast may be added to achieve the minimum weights.
2.5.3 Weight may be checked at the initial technical control, but the main
control of weight will be made at the end of practice sessions or at the
end of the race. The weight of the motorcycle will be that measured in
the form that the motorcycle participated, including normal levels of
oil, water and other fluids and all additional equipment attached to the
motorcycle, for example timekeeping senders, camera equipment,
electronic telemetry equipment etc.
For the 125cc class the weight checked will be the total of the rider
with full protective clothing plus the weight of the motorcycle.
Random weight controls may be carried out during practice in a
designated weighing area.
2.5.4 To remove the variable element of the weight of any remaining fuel,
motorcycles will be weighed without the fuel tanks for which a 2 kg
allowance will be made for all classes.
2.6 Fuel Tanks
2.6.1 Fuel caps must be leak proof and have a positive closing device.
2.6.2 Fuel tank breather pipes must include a non-return valve. Breather
pipes must discharge into a suitable container with a capacity of at
2.6.3 Fuel tanks must be filled with fire retardant material or be lined with a
fuel cell bladder.
2.6.4 The fuel tank capacities for prototype motorcycles are :
– 2-stroke engines : maximum 32 litres
– 4-stroke engines : maximum 24 litres
Taken from http://www.fim.ch/en/