1991 750

Valve lifter(rocker arm) tapping noise from left cylinder bank. What could be the problem? Looking for ideas on what to look for and test I could perform to identify the problem. I'll be removing the valve covers later this week?

remove the valve covers? You do realize that is quite a task. I would try to run "thinner" oil first to see if the noise goes away.
What weight oil are you using now?

Removed the valve cover and found one oil cowl plugged up. Clean and reinstalled, now when the engine is started all is quiet untill it warms up, then some low level tapping sounds. I wonder if the oil pump pressure is low?