The most reasonably priced component used on the Cb250 Nighthawk 1990 (l) Usa Gasket Kit A is the O Ring,10x1.6.
Some items from this specific schematic: Seal Valve,stem, Gasket,cylinder (nas), Gasket,carb.insul, Pkg,head Cover (nas).
On this parts fiche the Seal Valve,stem is the most specified component.
