I have a Kawasaki 14HP FC420V engine on a walk behind mower that has performed well since I bought it 7 years ago. While mowing it suddenly stopped and oil was then dripping from the mower. It probably dripped about a pint of oil. Oil and filter changes have been performed regularly. I haven't disassembled the engine yet, but it seems to have piston movement when I turn the vertical shaft.

Any ideas?