Ducati MULTISTRADA 1200S ABS 2015 Workshop Manual page 1086

Refitting the primary drive gears and checking backlash
Fully degrease the crankshaft splined end and the corresponding spline on the primary drive gear.
Position spacer (D) on the crankshaft.
Fit the driving gear (B) onto the crankshaft with the oil pump drive sprocket facing the crankcase.
Temporarily secure the gear with the washer (4) and ring nut (3).
If fitting a new primary driving gear (B), check the backlash.