These are the three pages out of the 1994 Sea-Doo shop manual. The XP number is for the 657x motor. It is a bit of a process to check it, see you are a hair off, pull the flywheel off and turn that stator just a hair, recheck, re pull, readjust. You might have to do it two or three times to learn it/get a feel for it.
The good news. Once it is set make sure the stator allen screws are nice and tight, tighten that flywheel nut down, put the rest back together and never worry about it again. Once it is set it is set for life.