Ducati Diavel Workshop Manual page 454

Fork - Steering head: front fork
Disassembly of the front fork
Restrain the counter nut (7) with a hex wrench.
Using another hex wrench, unscrew and remove the plug (14), with its seal, from the cartridge (8).
Unscrew the counter nut (7) up to the final threads on the damper (8).
While restraining the spring (10) with one hand, withdraw the bush (9) sideways and then slowly release spring (10).
Slide off the spring (10).
Slide off the preload tube (11) and recover the washer (16).