Buddy,
Yes, that is a real possibility. Those rods are aluminum of all things. I've already replaced them one time about two years ago. Very easy to do and there were no valves burned. I plan to check that tomorrow.
Eusa1,
Got your PM. Thanks. If I don't find a valve problem, that is the next thing I will check. Sounds like a big job though and I hope I don't have to do it.
This mower has just shy of 1700 hours on it now. I guess I can't complain but I know that when I bought it, I wished it had a Kohler or Kawasaki engine.