So I've been after this knock for a couple of weeks now and can't seem to solve it. If any one has ideas of what to check, that would be awesome.

2006 GS500F with 10k miles. PO dropped the bike once on the right side, I fixed most issues and the bike ran smoothly for the past 4k miles.

A few weeks ago, I had an oil leak coming from my valve cover. I pulled it apart, checked my clearances (all within spec, a little larger on the exhaust valves, but still within spec). I did not check the cam chain as I've never had issues with it and it appeared to be just fine. Prior to pulling all this apart, no knock existed. I was incredibly cautious not to drop anything while checking the shims. I reassembled, put in some new Brisk racing/performance plugs, had an issue with the bike not starting, so I pulled the carbs out again and reassembled. Started up after that. I did find another oil leak coming from my oil filter cover, so I dumped the oil, pulled the cap, and fixed that leak (after snapping a stud, of course). I did have some interesting stuff in the oil though. I had what appeared to be a *possibly* ceramic piece of a ring and some minor metal shavings. I do ride it pretty hard (but have never redlined it to my knowledge), so the shavings weren't too off-putting. But that little ring piece threw me for a loop. Not sure if it fell from something else in my garage or dropped down with the oil. I only noticed it hours later after I was dumping the oil. It appeared to be about 3/4" diameter and about 1/8" thick. The piece that dropped was less than 1/2" in length so I'm not sure if it was a  complete ring or not. I was able to break off a small piece by hand so I can confirm that it was a bit brittle, but I ended up tossing it thinking that it must have fallen from something else. I flushed the oil twice since then because I was curious and no other pieces fell. I replaced the oil with synthetic for the first time and it seems to be doing just fine.

With that being said, here's my issue. The bike starts kinda funny now. Full choke when cold, it won't start and I'll usually get a backfire. Half choke, it won't start. No choke, it starts, but dies after about 10 seconds. To get it started, I use no choke, then immediately set it to half choke and it will act normal from there. RPM's go up per usual given the amount of choke. It only needs a minute to warm up enough to idle without choke and the typical 5-10 minutes of running to reach a warm enough temp to ride however I would like. Idle is set to about 1300 RPM and will fluctuate a little. I found a vacuum leak around the intake boots so I fixed that and replaced the hose clamps on the boots to give a tighter seal around the carbs. That helped, but didn't do much for the knocking.

The knocking sound isn't so much a knock is it is a very loud chatter. Sounds to me like the exhaust is loose. I tightened both sides up, but no difference at all so I don't think that's where it's coming from. I also checked for cracks or any other exhaust issues but couldn't find anything. At lower RPM's, there is nothing out of the ordinary. At around 5k rpm and 3/4 throttle, it gets very loud. Let off the throttle and it goes away, get high up in the RPM range (over 8k) and it starts to fade or get drowned out. This happens in every gear and even in Neutral (revved in my garage to see if I could pinpoint it). Bike rides great despite the noise. The only riding issue I have is a little uneven power due to a stretched chain (which I will be replacing along with the sprockets). The sound does appear to get worse the warmer the bike gets.

Any ideas what to look for or test?

There was another knock posted up here a week or two ago, I think jack said that the starter clutch and cam end knock go away with higher rpm, but balancer shaft or rod knock might be quiet at idle and get worse with revs? Not sure, maybe he will chime in.
You could get a mechanics stethoscope and start poking around. That will atleast get you into the top or bottom end, and in the case of a top end sound you can usually figure out which cylinder is the issue.

Yea, I've been keeping an eye on the other posts and searched for engine knock help to see if I could figure anything out. I haven't had to dig down further than the valve cover before so this one would be a little new for me. What's different is that the sound is only audible during acceleration. I did narrow it down to the left side and also swapped the plugs for the older ones with no change. Put the Brisks back in since I much prefer the way they run. Here's a video with the sound. Sorry for the annoying throttle blipping, I wanted to show that the sound doesn't occur below 4k rpm or at steady rpm. It only occurs at 4k+ rpm and about half-3/4 throttle. It also goes away (or maybe just drowned out) by about 7k rpm. It is worse under load.