The component with the lowest price in the E-1 schematic is the Nut,hex.,cap 6mm.
Parts such as the E-1: Gasket Cyln Head (nas), Spark Plug(cr6hsa, Plug,spark (cr7hs, Washer, 12mm are included in the Cd50s Benly 1998 (w) Japan Cd50-240 E-1 parts fiche.
On this parts fiche the Washer, Sealing is the most specified component.