So I checked the valve shims, all within spec, put the engine back together. All straight forward, no issues other than I originally forgot to tighten the clamps holding the TB's on, did that at 11:30pm last night.

So now it chirps/rings under light-moderate load. I specify load because the throttle position at which it happens varies per rpm. Low rpm, it may only require 1/4 throttle to make it chirp/ring, higher rpm requires 1/2 or more. Considering it happens at any rpm, that tells me it's not vibration.

Also, if I turn the throttle past the chirping, it stops...until the rpm rises to a point that it's at that load value again and the noise starts anew.

Is that what knock sounds like in these engines? It's not the marble-like sound I'm used to hearing, but the fact it occurs only under light-moderate load has me concerned it might be. It's not the whirring I posted a video of, previously; it's a definite chirping noise.

It made it to work just fine, 47-ish iles. I'll ride it home just the same. I'll pull the airbox apart tonight and see if anything stands out as being 'wrong', but if anyone has ideas in the meantime, I'm all ears.