This International Standard specifies methods for evaluating the performance of engines designed for motorcycles as defined in ISO 3833, in particular with a view to the presentation of power curves and specific fuel consumption at full load as a function of engine speed, for net power assessment. Used in conjunction with ISO 15550, it is applicable to reciprocating internal combustion engines (spark-ignition or compressionignition) — excluding free-piston engines — and rotary piston engines, either naturally aspirated or pressurecharged and equipped with either mechanical pressure-charger or turbocharger.