Parts such as the Crankcase: Bolt,6x30, Gasket,reed Valve (mca), Bushing, Cover,control Valve are included in the Jf650-a3 Jetskix2 1988 Usa Crankcase parts fiche.
In this schematic the "Screw,reed Valve" is used most often.
The Crankcase assembly is constructed from several parts from which the Set-crankcase is the most expensive.