I have a Kohler 27HP on an 50" Exmark Lazer that's been to the shop twice with reoccuring problems. It started smoking when it had about 10 hrs on it. The dealer found that the lifters had collapsed and the push rods were bent. They fixed that. Then around 25 hrs or so it started smoking again. There was a bulletin from Kohler concerning the wrong pistons might have been installed at the factory. The dealer pulled the pistons and found that while they were the correct pistons, the rings weren't seating. So, they installed new pistons and rings. Now, the engine has about 60hrs on it and smoking again. Has anyone else had this problem? I called my dealer and asked him to call the rep and get me a new engine. This can't be good.