Abstract: A motorcycle of the type having a luggage box in the form of oppositely spaced side cases is organized to reduce the size and weight of the component parts of the vehicle by, according to one aspect of the invention, locating the pivot shaft for the luggage box cover, which attaches the vehicle rear seat, at the front end of the luggage box to reduce the stiffness of the frame parts required to support the cover. Also, the side walls of the side cases are adjustably secured to the vehicle and so configured as to permit selective enlargement of the cases without an attendant increase in aerodynamic drag. The vehicle, further, employs particularly formed side bumpers that are arranged to prevent damage to the laterally extensive side cases of the luggage box in the event of contact between the vehicle and the road surface that would otherwise damage the cowling.