I'll bet it happens with the carb down, due to the fact that when the engine is tipped that way oil will enter the breather chamber and then sucked into the carb. This is not uncommon when the mower is tipped that way. Only way to solve is to only mow with the carb up.
Thanks Rivets. I mowed w/ carb side up this week. It seemed to work. I did not have this problem when using Sears and Montgomery Ward mowers before on the same slope. Is there a mechanical way to rectify the problem w/ this Toro mower?
Sorry, but that's the nature of today's mowers. Have you made sure that your oil level is not too high. This would cause the problem to occur quicker. I also have a hill and I cheat. I keep the oil level a little low, but make sure I check the level every time I use it. I don't recommend this for anyone else, because I can repair my units a lot cheaper.