Ducati Diavel Workshop Manual page 459

Fork - Steering head: front fork
Insert the cartridge assembly (8) in the fork tube - calliper unit (19), screwing the tool 88713.3203 onto the cartridge.
Install the gasket (13) and the compression set screw (15) and tighten to the torque (Sect. 3 - 3, Frame torque settings).
Insert half of the prescribed quantity of oil in each fork leg (Sect. 3 - 2, Fuel, lubricants and other fluids).
Pump with tool 88713.3203 to force the oil to fill internal volume completely.
Slide both the damper and outer tube fully down the inner tube.
Pour the remaining oil into the fork leg and measure the oil level.
Important
Keep the fork leg vertical when measuring the oil level. Make sure the oil level is the same in both fork legs.
Recommended oil:
SHELL ADVANCE FORK 7.5 or DONAX TA
Standard capacity:
0.480 dm 3 for each fork leg.
Standard oil level:
104 mm.
The quantity of oil affects fork response during the final part of the compression stroke.
High oil level increases compression loading, low oil level will decrease it.
Clean off any oil from the spring (10) and the counter nut (7) before refitting.
Fit the following components:
the washer (16) and the preload tube (11).
Insert the spring (10), bush (26) and counter nut (7), with the conical side facing counter nut (23) and washer (8).