I am hoping someone can give me some guidance. I have been having some issues with starting my bike. I will try to explain the scenario the best I can.
The problem to me is that sometimes it sounds like the starter isn't engaging. But I can't seem to find a pattern to it. It seems random, some days it starts right up as if there is no problem, other days the starter motor just whines.
I ride the bike almost every day.
Some background info is that it is an 08 with 6500 miles on it. I just put a new battery in it in September. I do believe that it is charging, based on the tests I have done with the voltmeter. I have also tested with an ammeter to see if anything was drawing power off the battery while it was shut off and It didn't show anything. It has been doing this for a while now. The only thing I have touched is I replaced the stator cover. Is it possible that doing that messed up something with the starter clutch? (I am pretty sure however, that this was a problem before I replaced the cover.)
Here is some examples of what it has been doing:
So Friday morning the bike started and I rode it to class. That afternoon I went to start it after it sat on campus all day and it just whines when I pressed the starter button. I had to roll start it. By the time I got home I shut it down, and then started it and it fired right up. Friday night I rode the bike around town for probably 2 hours. I parked it around midnight in the garage. Saturday morning I went to start it and the starter just whined. I decided to take the battery out and charge it on a 2 amp charge for a few hours. I put the battery back in, and all it would do is whine when I pressed the starter. So I roll started it. Then I rode it around for about 30 minutes. When I got back I shut it off and then restarted it and it fired right up. Then I parked it, and this morning it started right up. I rode 100 miles today and stopped and restarted probably at least 15 times with no problems.

Sorry for the long post. Hopefully, someone can guide me towards fixing it. It is really annoying when you can't rely on it to start, especially since I ride a lot. Thanks.

I'm not saying with any certainty that this is your problem, but it happened to me. Last time o got that whizzing sound from the starter motor it was the brushes in the starter burning up. I had to find a rebuild kit on ebay for $25 or so.

Granted, the bike was much older (and not a GS500).

post a vid of the sound if you could

Ok. hopefully this video will give you a little better idea of what I am trying to describe. Here is the link:

http://www.youtube.com/watch?v=ULVMsUBgQVc

ok im not an expert with bikes by any means, yet it sounds like the starter motor is atleast spinning, possibly the starter crank on the flywheel is worn out and not grabbing anymore.
however if big rich thinks the noise is the same after hearing it it may be the bushes, yet it doesnt sound like it to me (again no expert) yet as bushes wear they can no longer spin the start, and im not sure if a bike starter has planetary gears like a car starter that can wear out either.
if you had access to a spare starter motor off anyone you could try it,
alternativly if you were to take off the cover from the left side of the motor (not just the sprocket cover yet the other one to, then crank it, you should be able to see if its spinning the gear and starter clutch. only do this if you cant test the starter motor another way, and no one else comes up with other ideas

put your hand over the tailpipe and see if you are getting any 'puffs' if there is no air movement then it isn't turning the engine over,...just .02

Gtscott is correct, I could very well be wrong. When my brushes went bad they were spinning the starter motor fast enough to make a whizzing sound, but not fast enough to engage the starter clutch.

you said the battery is charging, but is it holding a charge? The voltage really shouldn't drop too much in a 12 hour period.

Starter sounds OK. Possibly the gear on the motor shaft? The starter clutch in the engine? Loose starter motor?
Take the cover off the starter motor. Maybe the starter motor is lose and is not engaging  the gear in the engine. You can pull out the starter motor and see if its pinion gear is lose or worn out.
I wouldn't ever rebuild a starter for $25, when you can get nearly new ones from bikes that squids smash up with 1000 or fewer miles. I got one like that on sale for $12 to have as a spare.(Somehow I think there are 3 starter motors in the bike cave. I think parts reproduce during the night when I'm asleep.)

Sounds like a starter clutch issue to me.