These airheads make a few unusual noises, if you just came from Asian bikes .
The transmission noise in neutral is normal, my '81 has done it from the day I got it, coming up on 35 years, had the transmission rebuilt in '07, noise never changed after having that done either .
From what I've heard, one of the major issues with airhead gearboxes, is getting water into the transmission through a degraded speedometer drive cable boot, where the speedometer cable goes into the transmission .
I had bearing damage due to water contamination of the transmission oil, found this in '87 .