coffee grinder syndrome is a know issue that affects some vn750's. under certain conditions, the clutch plates will stick/chatter on the clutch disks when you start to release the clutch, and it sounds like a coffee grinder. along with the sound, you can experience jerky engagement of the clutch.
its not 'harmful' to the motorcycle.
there is a TSB (technical service bulletin) from kawasaki about it, and it involves drilling a series of holes in the clutch basket to allow more/better oil flow.
**NOTE** this does NOT affect all Vn750's, and its across the board as far as what years suffered.