Did you soak the plates in oil before assembly?
I had a noise that I described as a "spooling" sound sometime after I replaced the clutch in my 74 CB550.
I remember thinking a bearing was going out, due to the vibration/chatter/growl under certain engagement conditions.
This was over 10 years ago. I don't think I soaked the plates in oil before assembly then.
It went away after I re-adjusted the clutch actuating mechanism. The noise never returned.
Maybe this was when I learned I was supposed to soak the plates first. I have a fuzzy memory about clamping the clutch lever disengaged overnight, too. Theory being that with the plates separated, oil would seep in and soak the plates in situ.
FWIW
Cheers,