Parts such as the Crank And Piston: Piston Ring Set (2ndo/s), Piston Ring Set (2nd O/s), Brg,r-b 6304c3 52mm 144g Ky, Pin, Piston are included in the Yl2c 1967 1968 Usa Crank And Piston parts fiche.
In this schematic the "Washer (29l)" is used most often.