An air cleaner chamber is configured such that a filtering member is held between an air cleaner cover and an air cleaner case. A low-speed operation air intake passage and a high-speed operation air intake passage share an outlet passage portion near a dusty space, and are molded integrally on the air cleaner case using a synthetic resin. A passage switching valve is disposed so as to switch an aperture area of the high-speed operation air intake passage. In addition, a valve actuator for driving the passage switching valve is mounted to the air cleaner case.