I would start by removing any clutches if still mounted on the mower, and also remove the flywheel. If the clutch bearings lock up or the magnets come loose from the flywheel will give the appearance of a seized engine.
Did the engine make any noise when it stopped running? Is there a mouse nest under the engine housing? Try placing a 5/8" 6-point socket on the bolt at the bottom of the clutch and see if you can rotate the engine in either direction. It happens. Two weeks ago, I had a customer with a Cub Cadet XT1 and a Kohler 5400 with 138 hrs. on the meter, and it seized dead solid for no apparent reason. It is very unusual, but it does happen. In the end, he chose to replace the engine with a drop-in, considering the engine cost with labor was less than one-third the cost of a machine replacement. I serviced that machine back in April with Valvoline 10w30 full synthetic and a Wix 51348 filter (Napa Gold). That's the first of the newer Kohler KT series engines I've seen fail with no outside reason. I contacted the local Kohler rep to ask for courtesy assistance. He came to my shop to verify, took an oil sample and two days later he (Kohler) offered to provide a new drop-in engine at "dealer cost" ($632.00), fair enough, given it was 4 years old. He picked up the failed engine last Thursday to ship it out for engineering analysis.
I have not heard back from the Kohler rep, maybe I won't. But he was very fair, and part of his decision was that I had the service records as well as the low hours.
I have not heard back from the Kohler rep, maybe I won't. But he was very fair, and part of his decision was that I had the service records as well as the low hours.
I am sorry to hear it. I would get in touch with your dealer and request the Kohler representative's phone number so I could give him a call. Attempting it will not harm you. Lubrication failure is nearly always the root cause of such a catastrophic disaster. Second possibility, running above rated RPM's.
