Second try getting Roxy started.
Compression test was good, coming in at 110 cold.
Played with the carb settings a bit and actually got a couple coughs and even an idle that lasted for a few seconds. At that point, at least I knew it had the possibility of running.
Immediately decided to swap out the carb to be sure. Went with the Sheng since it had also been a runner before.
Swapped over easily, deciding to loop the gas line so it wouldn't be as hard to remove later.
And... she starts right up!!
Good news, she's a runner again. Slightly bad news, not sure what's up with that Keihin CS90C. Hoping to get that sorted out so it's solid again.
Let her idle for a few mins and she ran fine. Shut her down for a bit then started again and she came right up.