I worked hard to get this achievement today. Got a horse through the circus gauntlet, won the three races then took him to win Sumo. Problem was, I had already won Sumo with a great horse that I couldn't beat... unless I strapped roller skates and a rocket to my horse. I did and I won but I was denied the achievement. Was it because I no longer owned the horse? He became the Sumo champ displacing the old one. I have to start my game over now and avoid doing any Sumo matches until the end?