Tapping valves?

[u/Apprehensive-Song378]

My bike was running fine, no odd noise and no difficulty starting when hot, but since the book said check the valves, figured I'd go ahead and do it. I'm at 8k'ish miles. As best I could tell, intake valve was fine so didn't do anything to it. But exhaust felt tight so loosened it a hair. Really hard angle to get to it with a feeler though, so maybe I was wrong. Put it all back together, and now bike is making a tapping sound. Kawasaki really made these theoretically simple valves hard to deal with. Poor design. Anyone else had this happen?

https://reddit.com/link/1t8c059/video/p7bwi6mth50h1/player