This GASKET KIT B assembly utilises two O-ring 7x1.7(s) - the highest specified component.
Some items from this specific schematic: Oring 183, O-ring 7x1.7, O-ring,13.8x2.5, Gasket,r.cover (mca).
seven components are shown in this Cb250rs 1980 (a) Belgium Gasket Kit B exploded diagram.