One reason would be that the float valve may be sticking in the carburetor and letting gas flow by and into the engine when the mower is not running.
The other thing I have seen cause this is one cylinder is not firing and that cylinder lets the gas by the rings and into the crankcase.
Most of the time it is the first thing I listed.
You can change the oil and install a shut off valve in the gas line. After you mow just shut off the gas valve. That will let you know if that is the problem. If it takes care of it you can either have it fixed or just use it with the shut off.
The most common reason would be the ignition coil is bad. The worst reason would be a broke rod, but you should be able to a rattle inside the engine where the broken part is knocking!
Maybe no juice in the battery.
Typically this is caused by a bad seat safety switch.
how much would it cost to bore out a 12 hp briggs and stratton riding mower motor
A dead battery would not cause an engine to seize
What would cause the engine not to restart when hot Chevy Trailblazer 2007?
No, it would cause the engine to run poorly but not to seize. Lack of lubrication or overheating will cause that. Also a broken part, as in a rod, will cause it to seize.
There is not such conversion of displacement to HP. You have what is basically a 17 cu. in engine and that would seem to be and 8 to 10 HP engine in an OHV configuration.
0.004" would be correct. See the YouTube link attached below for the procedure.
Many things could cause an engine to shake. One, for example, would be low coolant or oil levels.
Driving through flood water would cause the ignition to fail and stall the engine.
most snapped timing belts will in most cases cause engine damage,the only exception would be a freewheeling engine were valve to piston contact would be minimal an interference type engine would cause damage.