Those Kohlers are known fro loosening the 4 crankcase bolts nearest the cylinder then cracking the crankcase down on the exhaust cam side.
SO make sure they are all tight, annual check.
Cure was some locktite on them.
On some i service they bolts still come loose due to the threads being worn from loose bolts.
So when they come in I fit helicoils, one at a time because the owners don't want to pay for all 4 at once.