I bought an older model "late 90s I think yellow deck" John Deere 48 inch 17 hp kawasaki commercial walk behind. The guy that had sold it to me because he got it free. I didn't think it was that bad, but when it starts it is extremely loud and seems to vibrate, . It has 525 hours on it and mows like a brand new one and runs great. I had 2 small engine places look at it. 1. said the balancer had came lose on the shaft. 2nd said it had a rod knocking. My thought is I'm going run it, for as little as I have in it. If anyone has any suggestions please let me know..