Vacuum quwstions and what would cause float needles to stick?

[Shift-E]

So I recently cleaned and rebuilt my carbs, including new gaskets, orings, and float needles. Shortly after this I started having, what I think are, vacuum and idle issues with the frame petcock set to "On", and the bike would want to rev high and stall, I think draining the fuel line faster than it could fill it. Switching to "Res" or "Pri", I was able to ride okay with the gravity feed system rather than vacuum. That was until today, when the bike started giving me issues with idle after it got really warmed up, and it started stalling again. It rode alright for 50 kilometeres before doing this.
Yesterday, setting the bike to PRI didn't cause any fuel overflow to come out the airbox. Today, while trying to troubleshoot, it did. I haven't had this problem of floats sticking since before I cleaned the carbs.
What could be causing the floats to stick out of nowhere if they were recently cleaned? (Less than 150 kilometers/100 miles ago) Could vacuum problems cause this issue? Could more dirt really have gotten in there?
Repairing this bike will be the death of me.

[Shift-E]

Nothin?

I drained the floats and tapped on the float bowls until I could hear the floats bouncing up and down and functioning with a proper range of movement. I also took the spark plugs off and blasted some gas out of the left cylinder (right side was fine, issue seems to only be on the left carb/cylinder). Letting it sit with the plugs out to get a good air dry, then buying new spark plugs just in case I need them.

[78530i]

Similar issue here after rebuilding using k&n kit. Those needle valves are suspect.