This can be one of several problems.
I would first pull the valve cover and check the clearances. Being an OHV it is possible that valve clearances have open so much that the ACR no longer works. Also while checking and adjusting look for the decompression bump. Usually on these it is on the intake valve. If there you're good. (ACR = Automatic Compression Release)
If the bump is not there then you have a failed ACR on the camshaft. These engine uses 793880 camshaft on which the ACR is a known weak area is prone to sudden failure.
An non-operational ACR cause also be the cause of the starter solenoid and possibility of a damaged starter as the operators will tend to use a larger barttery to jump start these engines. Just a heads up on this.
Of course there is a possibility that a valve has move causing a bent push rod.
Also with this many hours on the engine I would do a leak down test since these also have a head gasket that tends to blow between the cylinder and the push galley. Basically just for peace of mind as this causes the engine to burn oil; sometimes without anyone noticing until after the engine due to no oil in the crankcase.
