Parts such as the Camshaft - Valve: Valve,exhaust, Screw,tappet Adj., Shaft Comp.,cam, Spg,valve are included in the Z50j5 Monkey Japan Camshaft - Valve parts fiche.
On this parts fiche the Cotter,valve is the most specified component.
The most reasonably priced component used on the Z50j5 Monkey Japan Camshaft - Valve is the Nut, Tappet..