my '77cb550 starter was making similar noises when cold, worked fine when warmed up. the starter bench tested fine, another good starter made the same noises. i was advised that the starter "sprag/clutch" was in need of repair or replacement. access could only be made by splitting the cases. i later sold the bike, advising the new owner of the particulars. the bike was tuned well, and started first kick every time, so he didn't seem to mind.