The other day one of my guys was running one of the lazer mowers, and all of a sudden the engine started knocking and smoking. We changed the oil 3 days prior, and there was oil in it, but burnt bad. The exmark dealer told us that the spark plug was busted in the engine. How i don't know, the guy was on an open field, and it had been run at least 20 or so hrs. I am hoping that this is covered, but I just thought that this was really wierd. Any of you ever had a situation like this.