125cc and 250cc classes

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 The new class will be called Moto2. Engines will be produced by Honda; electronics will be limited and supplied only by FIM sanctioned producers; carbon-fibre brakes will be banned and only steel brakes will be allowed. However, there will be no chassis limitations.