What was your comp reading on the low pot? Did you try putting a teaspoon of oil into that cylinder to see if the numbers came up? What did the plug out of that cylinder look like? Is the bike puking oil around the base or head gasket? Did all this, the reason you pulled the carbs off and the valve adjustment crop up over night? When's the last time they were adjusted? It's possible that valve was soo tight it wasn't closing and on the exhaust side that could spell bad news, as in torched valve= low compression. But you would probably be able to see that on the leading edge of the valve if you look down into the plug hole and rotate the motor till the valve opens...
I'm not trying to be a jerk so sorry if it sounded that way but if the bike was running well before (certainly sounded so in your video) what happened? Lots of these to check to give you clues. A leak down I suppose will help, but depending, it may not show you anything except your bike is leaky... Yanno?
I admit at first I was like, woah! But it really sounded like you didn't slog through all the posts, came in at the end and was like, wtf that doesn't make sense... and you're right it doesn't. Most of the info you ask has been covered already but here's a brief synopsis of the story:
The bike has always been slightly cold blooded, (which I'd assumed was normal for it but I've learned it isn't) but ran really well otherwise. This past year the bike has become downright cantankerous when cold, and top end performance is noticeably not what it was. I've also noticed in this time my valve clatter has all but disappeared. Obviously it's time for me to address maintenance items which I've put off for too long. First up was to be checking valve clearances, and replacing the half moons some of which were leaking quite a bit of oil. I also figured intake O-rings were ready for replacement, and when I saw water blowing from the intake area when the bike was wet I decided the time was NOW. The bike did not really leak oil other than from the half moons and maybe from the tach drive, but mostly the half moons.
I took the carbs off, replaced intake o-rings, cleaned the carbs thoroughly and put all new o-rings in. At the same time I took off the valve cover, checked valve clearances, of which all but two are below .05, my smallest gauge. Then I took each shim out one at a time to measure and inventory them, to try to figure out what I need shim wise. I used a zip tie to hold the valves open. As I noted, the exhaust valve for cyl. #2 appears dirty on the seating area, so it's at least dirty, maybe burned. Nonetheless after I did all this I put it all back together with clean carbs, and the bike won't run. Before fiddling further I did a cold compression test, and cyl number two has almost ZERO compression, with and without oil. All the numbers are given earlier in the thread, you can pick them out easily if you look. Basically number two is dead, three is low, and four is way high, which sounds to the folks here as if the cam timing is off. I forgot to mention I turned the crank by hand a couple times when checking valves before I remembered to put the tensioner back in
... As per advice I took the cams out, rapped on the valves with a wooden dowel and a hammer, reinstalled the cams carefully, and I'm still getting the same compression readings. I will try timing the cams AGAIN, to be sure I have it right, but I still suspect that the cam chain never jumped on the sprockets. Nonetheless SOMETHING happened to make a running bike not run, and that something was perpetrated by me, either directly or indirectly.
The bike still obviously needs the valves adjusted, carbs tuned, etc, but it's not going back together until I solve the mystery of the crazy compression, which may well mean taking the head off. For sure there is some ring wear too, as three cylinders had higher readings with oil, but it may not need a ring job, at least for a while. The thing about the leak down test described by Dan is that it's not the one used on aircraft engines - it's not as practical on bikes. What you do is take the carbs and the pipes off, take your oil cap off, and hook up about 20 psi to your cylinder. Listen at all three locations, and you can get a general idea if something is leaking abnormally - rings = crank case, intake valves = intake ports, exhaust valves = exhaust ports.
That's mostly where I am with this now, and thanks for trying to sift through my mess.
) and see where that gets you. You never know.. it may solve at least HALF the problem. Otherwise, a tear down, provided you have everything on hand, and dont need serious machine work, is a weekend job 
You'll get it sorted, we'll see to it. If not, I will send darling Rose over with her shotgun 
