Ducati MULTISTRADA 1200S ABS 2015 Workshop Manual page 876

Reassembling the oil pump
Check that the spring (8) and key (6) are present on the pump.
Fit the pump drive gear (7) on to the oil pump and secure it by installing the circlip (6) in its groove.
Insert by-pass valve (5), spring (4) in the pump and tighten plug (3) to a torque of 17 Nm (Min. 15 Nm - Max. 19
Nm) by applying medium-strength threadlocker.