Well its not the rings ..the only way gas can get to the oil is thru the carb ..you proably have a needle and seat problem letting gas over flow while it sits and drain into the oil chamber
I had the same problem it was fine until I let it sit up for a week or so then there would be gas in the oil ......I just put a gas turn off vavle in fuel line and it fixed my problem ....good luck
bg
November 2007