The most reasonably priced component used on the Kl650a3 Klr650 1989 Usa California Canada Muffler is the Bolt-flanged,8x16,bla.
Some items from this specific schematic: Body-comp-muffler, Nut,8mm, Gasket,6.2x11.5x1.5 (nas), Holder-exhaust Pipe.
On this parts fiche the Gasket,6.2x11.5x1.5 (nas) is the most specified component.