A sample from the products for the Crankcase include: Ring-o,od=18, Pin,3.5x6x16, Plug,main Gallary,18x, Tube-assy.
On this parts fiche the Gasket,10x14.5x1.5 (nas) is the most specified component.
The lowest price component in this Crankcase parts-list fiche is the O Ring,10mm.