Ducati MONSTER 821 Workshop Manual page 840

Fit the impeller shaft (6) with the previously installed mechanical seal (9).
Insert the spacer (8), aimed as shown in the figure, and lock in place with the snap ring (7) duly inserted
inside seat (G).
Turn the impeller (6) and make sure that it can rotate freely, without excessive resistance.
Clean the mating surface thoroughly on the pump cover and on the generator cover.
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