Has anyone else had this happen? Our ZTR has sat all winter with mostly the gas valve OFF. There seems to be gas in the oil now. (I think it's happened before, too) We're going to our dealer today to check on some Toro 21" push mowers, and we'll talk to him about it, but has anyone else had this problem? We've had this happen to 2 engines before, and it eventually led to their demise from cylinder scouring, etc. WE ARE UNDER WARRANTY!