Hummm I don't know of any for ATV's specifically. I know there is a few for cars but I'm not sure if I would try it in a ATV or not. I think one is called Engine flush. If you use it I wouldn't run the engine to long with it in there. I would probable just try draining out what you have in there..put in yamalube ..run for a few miles...drain...put in fresh yamalube again and you should be ok.

 

Just drain the old oil, put some new motorcycle/atv oil in, ride it around for 10 or 15 minutes, then drain the oil, and put new oil and filter in. That should flush out 99.9% of the bad oil.