Suzuki DR650 Wiki

You can make your own damper rod tool from a 3/4" x 1-1/2" - 10 tpi bolt from your friendly local Ace Hardware store. The bolt head is 28.3 mm across the flats and fits the 30 mm hex opening in the top of the damper rod well enough. Slide a socket wrench over two nuts and a lock washer on the bolt, and with a 14"+ extension, you can slide the socket, bolt and nuts down the fork tube.[1]

You can also make a more snug fitting tool by using a 1" square nut, slid over a bolt smaller than 3/4" and jammed using two hex nuts and a lock washer.

Damper rod tool

The second mentioned tool. 1" square nut.