Parts such as the Fuel Tank: Rub,radiator Mtg., Screw-washer,5x25, Rubber,cap Cover, Screw-washer,4x16 are included in the Gl1500c Valkyrie 2000 (y) Austria Fuel Tank parts fiche.
Check out any of the thirty-three Fuel Tank components enlisted.
In this schematic the "Screw-washer,4x16" is used most often.