A throttle valve comprises an intake passage. A throttle shaft extends in a generally vertical direction. The lower end of the throttle shaft passes through the throttle valve and projects downward. A throttle lever is connected to the downwardly projecting lower end. The throttle lever is joined to a throttle wire. A fuel injector attachment seat is positioned on one side of the throttle shaft and an intake pressure sensor attachment seat is provided on the other side of the throttle shaft when viewed in the direction along the intake passage.