I would pull the valve covers. Watch the valves go up and down. They should all move roughly the same in travel distance. Put a straight edge on a rocker, watch the valves move. Look for a valve that doesn't move at all. While you are there check lash.
I would check flywheel key, valves and fire on both coils jumping a 1/4"+ gap in free air.
Vapor lock doesn't happen on mower engines. That is an old school 1968 Olds-Mo-Dodge trick back in the day.
Head gasket/s blown externally. Put your fingers around the head to block area and also look for black carbon exhaust leaking out.
Smoke can find leaks too. Get out your evap smoke machine and smoke the oil sump. Should pour out all the leaking areas.
You can also pressurize the oil sump with shop air at about 10psi. Listen and feel for air leakage again.
Flush out your mower fuel can. Make sure you don't have a pile of grass and dirt in the bottom. If you do, every time you gas up the mower, all that trash passes to the mower carb.
Get a new style mower fuel can. If you have an old can with an open top, you are making trouble for yourself. New cans are sealed better than the old ones. Fuel cans are highly over looked items.
Most likely your carb is polluted.
I would check flywheel key, valves and fire on both coils jumping a 1/4"+ gap in free air.
Vapor lock doesn't happen on mower engines. That is an old school 1968 Olds-Mo-Dodge trick back in the day.
Head gasket/s blown externally. Put your fingers around the head to block area and also look for black carbon exhaust leaking out.
Smoke can find leaks too. Get out your evap smoke machine and smoke the oil sump. Should pour out all the leaking areas.
You can also pressurize the oil sump with shop air at about 10psi. Listen and feel for air leakage again.
Flush out your mower fuel can. Make sure you don't have a pile of grass and dirt in the bottom. If you do, every time you gas up the mower, all that trash passes to the mower carb.
Get a new style mower fuel can. If you have an old can with an open top, you are making trouble for yourself. New cans are sealed better than the old ones. Fuel cans are highly over looked items.
Most likely your carb is polluted.