On this parts fiche the Cotter, Valve is the most specified component.
The most reasonably priced component used on the Xv1100 1997 3lpf Spain 273lp-352s1 Valve is the Nut, Hexagon.
This schematic depicts all components used in the Xv1100 1997 3lpf Spain 273lp-352s1 Valve partslist.