Take my advice as a grain of sand in the wind because I have not worked on this pump personally.
But it looks the same as some of our bosch pumps on our Valmet engines.
If so, their is a stud with a locknut under that square plate on the back of the governor housing. Loosen the locknut, and turn in or out one or two turns. (I can't remember which way)
If I were you, I wouldn't pay attention to what I just said, and I would join 4btswaps.com. They could tell you how in about 2.2 seconds :Cheer: