In this schematic the "Bolt,flange,6x25" is used most often.
Parts such as the Water Pipe/thermostat: Seal,water Pipe,2, Pipe L,water Outl, Wash,special,12mm, Seal,water Pipe 2 are included in the Gl1500c Valkyrie 1997 (v) Germany Water Pipe/thermostat parts fiche.
The Bolt,flange,6x14 is the cheapest item from this partsfiche.