According to multiple sources, including, Moto3 bikes use a 250cc engine with a single cylinder that produces around 60 horsepower. Moto2 bikes use a 765cc three-cylinder engine that produces around 140 horsepower. MotoGP bikes have a maximum engine capacity of 1000cc with four cylinders that produce around 250 horsepower. Therefore, the engine capacity of a MotoGP 3 bike is not a valid question as there is no such thing as a MotoGP 3 bike.