Your bike does not do what I think it should be doing. You say the idle is high when cold and then drops to 500 when warmed up? Are you using the Chokes? Sometimes called Enrichners. Your bike has a lever attached to the left side of the Airbox with cables that go to the carbs. This is the control for the Enrichners. It is to be used when starting a cold bike. Are you using the Enrichner when the bike is cold, it idles high, and then turning it down later when the bike is warm and the idle is now 500 rpm.
An idle when warm of 500 rpm is a little low.