An engine includes engine valves disposed on intake and exhaust sides of a combustion chambers with a valve operating device for opening and closing the engine valves and an engine valve disabling mechanism for disabling opening and closing movement of the engine valves in response to hydraulic pressure. An oil pump is disposed in a lower portion of the crankcase, for supplying hydraulic pressure to the engine valve disabling mechanism. A hydraulic pressure control valve controls the supply of hydraulic pressure to the engine valve disabling mechanism depending on a vehicle operating state. An oil passage extends to the hydraulic pressure control valve and can easily be formed without affecting mounts for functional components. A pipe for delivering working oil from the lower portion of the crankcase to the hydraulic pressure control valve is disposed on a front surface of the engine.