I am no expert, but, I have a Sears Lawn tractor that was did that a couple of times. The last time it blow athe exhaust valve seat.
I order a new valve and gasket kit for it, after receiving the parts I dismantled it only to find it was not the valve broken as I originally thought, but the valve not seating properly into it's exhaust port.
The exhaust valve sleeve became lose.
I reseated it and now I am on this dam site trying to find the torque specs for the Head.
Does anyone know what are the correct spec for the head bolts so I can get this thing back together and finally cut my grass?