I've had two head gasket jobs done on my Kohler 25, a new carb and last week the head gasket went again. I've complained and complained to my dealer about lack of power many times. This time I asked him if he'd put in a new motor for me. He said I should call Kohler and ask them myself. I did, they asked to speak to the mechanic, so I handed the phone over to him. They asked him what the "spec" number was on my motor. After he told them, their answer was, "That explains it". The next day the dealer faxed copies of the service records to Kohler and my new motor was shipped that day, next day air. Kohler said it's the latest design they have at the moment and it should hold up better. For a brand new motor it runs very strong. I'm using double blades and I can't sense any less power than when I was using single blades and the mower was new.