I recently changed the oil in my 1986 yamaha virago.  When I am riding and I release the throttle my engine coninues to rev at a high rpm for a significant amount of time before returning to a normal idle.  This is causing the bike to to to superheat.  Can anyone give me any advice on what I should do first or what may be the cuase of this?  

not sure how changing your oil can cause the high revs. first thing i would check is the return spring on your throttle, probaly spray some cleaner and see if that helps. does your throttle grip return to off position when you release it?  

The throttle does return to it's original position and I just threw the oil change in there because that is the only thing that I had done to the bike recently.  The problem only seems to happen after I've been riding for about 30-40 minutes and the bike has warmed up.  I'm starting to think it's heat related???  

Is this something you noticed this year vs last year?

It's possible that the Ethanol is messing up your settings. I'm not quite sure how, the regular mix, and the ethanol blend should be responding similarly...

I'd do the full carb adjustment Pilot thru main (after pumping some carb cleaner thru the tank.