Well it has never happened to me before but my kawi 23 horse on my 737 dropped a valve through the piston. 1763hr on the machine. The valve broke off right at the head and sent the piston into a hundred pieces. The bad thing was that it blew up the day I was schedule to leave for Florida for five days so I will have been down a week tomorrow and finally ordered the parts today. Probably end up costing my about 200 bucks or so for the piston, valves, and rings, gasket. I am just glad I am not having to pay deere to do it. Anybody else had this happen before with the kawi engine? My mechanic at the dealership said he had never seen one just break off like that. He had seen the keeper come off the valve but not this.