Ducati Diavel Workshop Manual page 744

Clutch assembly: primary drive gears
Withdraw the clutch housing (1) complete with driven gear of the primary pair (A).
Remove the inner spacer (2).
Remove the oil pump (D) (Sect. 9 - 2.1, Removal of the oil pump).
Lock the primary pinion (B) with the holding tool 88713.3417 and loosen the threaded ring nut (3) using the bush part
no. 88713.3406.
Remove the nut (3) and safety washer (4).