In this schematic the "Bolt" is used most often.
Parts such as the Air Filter: Reed Valve Assy, Stopper, Reed Valve, Ybs83-530 Screw,panh.tapping, Clip(3vr) are included in the Ce50et 1987 Riva Jog Air Filter parts fiche.
The component with the lowest price in the AIR FILTER schematic is the Bolt.