Parts such as the Cylinder Head: Plug,spark, Guide,ex.valve, Plug,spark, Bolt,flange,sh,6x25 are included in the Xl500s 1980 (a) Usa Cylinder Head parts fiche.
This Head,comp,cyln is the most expensive of the items that make up this Cylinder Head assembly.
In this schematic the "Washer,8mm" is used most often.