Oil light comes on at low rpm

RESOLVED: I finished re-installing the oil pan, clutch, and exhaust on Wednesday, then filled her up with 20w-50 (instead of the 10w-40 recommended on the filler cap), and went riding all afternoon yesterday. The oil light stayed off and pressure was normal (30psi warm @4k rpm). With all the work I put in, I'd like to think that something I did in there contributed to the solution, like cleaning the pump screen or sanding the pump cover, but the key factor was probably the heavier oil weight. Even if it turns out that taking the bike apart was unnecessary, I sure did learn a lot about my KZ, and I'll feel much more confident if I need to work on it in the future. 

Big shoutout to everyone who offered help or insight along the way. Thank you very much for sharing your knowledge and experience.

-Max
 

Good result !  

Keep an eye on it