Parts such as the E-13 Crankcase: Cap B,oil Path, O-ring,15x2.5, Bolt,flange,6x40, Washer,8mm are included in the Cb650c 1981 (b) E-13 Crankcase parts fiche.
The most reasonably priced component used on the Cb650c 1981 (b) E-13 Crankcase is the Bolt,flange, 6x32.
Check out any of the eighteen E-13 Crankcase components enlisted.