Carb in your hand looking in the bell end of the carb the slide usually has a small gap under it that the idle screw adjust. How much open ?  shaft of a drill bit 1/16” would slip under slide without touching, a 1/8” would be a large gap and very high idle. You should be able to raise or lower slide w / adjustment screw. Might bind trying to raise so a little throttle pressure helps .
  
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Tried the other idle adjust screw all the way in, no dice. Also put the clip in the second groove of the needle and that didn't help either.

RT - thanks for the info on the reeds.
I recently replaced all the crank seals during a bottom end rebuild when I first got the bike. I did use a speedi-sleeve to get a better sealing surface since the old one was worn down quite a bit. Really hoping it's not that.

It only catches again at the end of the video because I grabbed the throttle again. If I had not done that it would have stalled out.

What do you mean by the base gasket?

Ok thanks for the update. On twostrokes it's possible in extreme case to have the cylinder base gasket either blow out usualy around the transfer area on the sides so would be obviously hanging out the side & letting air in causing lean running.
In a 'not so obvious' case it can get sucked in along the side with same result except not as easy to see as nothing sticking out but still letting air in.

It is displaying the symptoms of a non-functional idle  circuit in the carburetor. You mention cleaning the pilot jet carefully. Did you also assure the pilot jet circuit (including the nearly microscopic passages in the body) is clear? I've used aresol cans of carb cleaner that have the "straw" attachment to both flush and verify the passageways followed by compressed air to remove any residual liquid. Of course, being careful not to get hit with any spray back.

The whole thing was ultrasonically cleaned once, but I only focused on the jets with my hand cleaning afterwards. This sounds like the next box to check though, thanks.

There comes a time when a machine can’t preform like the hand of a human does… Using such as a guitar string to poke into the passages of those jets is the only the way to be sure..
Sneezles61

I save some accupuncture needles about 25 years ago. Good for pilot jet cleaning haha.

Alright, two nights and 2 carb cleans later using guitar strings, aerosol cleaner, and compressed air... and I got a tiny hint of an idle. Now it putters out for maybe 2 seconds instead of instantly dying! Changing the idle screw and air screw does not help with anything though.

I am at a loss at this point. I KNOW it's not the carb body passageways or jets being clogged. Maybe I need to size my jets differently??

just had similar issue with a AT2MX - new carb - no idle - would start right up - rev fine and them die!

I had to adjust the float level - I had set it to the new carb to factory spec for the old carb at that time - the new carb had a recommended setting, so I went back to that, and she runs and idles normally now.
 

I'm out of ideas without being there sorry.
No air leaks.
Crank seals ok.
Couldn't see a speedy sleeve causing an issue

I keep finding this guys very good informative videos when googling for anything yamaha lately so here's a link incase its of some use.
Not sure i'm keen on drilling the seal but that's how others do it.
Knowing my luck i'd drill the bearing or break the drill off.
Just do it carefully i guess.
At exactly 10.15 if you set it to slow mo i think there's a fraction--gnats whisker--of play between crank & bearing.
Any play isn't good as is a press fit on that side. But isn't going to affect it until it gets worse & i'd do it next time--if i'm right in what i thought i observed--gotta look close & the oil sitting there gives a clue.
Anyway, what was i talking about--you used a speedy sleeve on yours which is interesting as i've never used one but sounds great. Did you have the sleeve fitted by a machine shop.