What is this starter sound?

I have a 1979 custom 12k miles runs great. Its cold now. I've been getting weird sound from my starter. The sound comes and goes. It usually comes on after like a minute of trying to start. A hard start. I got the bike this fall. Never made the sound. Once it got below freezing and I didn't ride it for weeks at a time, it would make the sound during the longer times it took to start. Once it started, the sound would go away on warm restarts. But when cold some machinery definitely changes, and there's a very different bad sort of sound after a minute or so.

[REVISING TO ADD INFO ON THE HARD START: Whew, it took like 5 minutes of cranking to start this last time. I vary all the options. Is there a standard way to hard start in the cold? I try choke out, choke in, throttled a bit, twisted a couple times, no throttle. Sometimes it starts turning over with starter still engaged then it quits when I release the button. In the warm weather it often only takes like a 1/2 second to start -- touch the button, bang. So nice.]

Can you tell me what's happening with this sound? Here's a link to the Youtube....