That thing is air cooled, right?
If so, all you've got for cooling is the fins on the engine and the oil. Are the fins clean and clear of grease and debris? Have you recently painted the fins? I have heard from a few people that engine paint can cause issues because it likes to hold the heat. Aluminum has really good heat transfer properties. It heats up quickly, heat transfers through it quickly, and it cools down relatively fast, which makes the air cooled system work well on it.
I would check that oil level before riding it. If the glass is jacked, find another way to check it. You can stick a piece of wire into the fill hole, and use that as a dipstick. Might be your best bet. I don't see fuel-air mixture problems causing it to overheat. Also, if you do have sufficient oil in there, it could be that the oil is not moving properly. When is the last time you changed it? Maybe some passages are clogged?