In addition to the good advice provided in the above post by Randy T you may also Want to do a compression check.I would remove the valve covers and check the push rods to make sure they are still in place and check valve clearances before going through the operation of removing the flywheel to check the key which is very rare to be damged on riding mowers due to no direct drive that would cause shock loading to the engine. A dropped exhaust push rod would cause the same effect.
I agree with you ...going to check valve clearance ... Thanks !I would remove the valve covers and check the push rods to make sure they are still in place and check valve clearances before going through the operation of removing the flywheel to check the key which is very rare to be damged on riding mowers due to no direct drive that would cause shock loading to the engine. A dropped exhaust push rod would cause the same effect.