Parts such as the Swing Arm: Pin-cotter,2.0x15, Bolt,flanged,6x55, Adjuster-chain, Arm-comp-swing are included in the Kdx250-b1 Kdx250 1981 Usa California Canada Swing Arm parts fiche.
The component with the lowest price in the SWING ARM schematic is the Bolt,flanged,6x45.
On this parts fiche the Cap is the most specified component.