I put my carbs back together and ready to put on the bike so I decided to do a quick oil change before I attempted to start it. I unscrewed the dip stick and the oil stank of gas... what would have caused gas to dump in with the oil like that?

Most likely, bad float valves. Bike sits, gas seeps past the floats, fills up the carbs, and runs into the engine. Fuel seeps past the rings and into the oil. A bad petcock can contribute to the problem; if the petcock closes properly while the bike is sitting, fuel shouldn't be flowing into the carbs.

just tore into my carbs again and realized that the valve seat is loose. thanks for the info!

Awesome. Glad that helped.