mower won't start when hot.
after cutting half the lawn the mower stops and will not restart.
First check the vent in the gas cap. If it is not working, a vacuum will build up in the tank and starve the engine of fuel. After it sits for a while the pressure will equalize and it will be able to get gas again. Also if it has coolant, check the level.
If the starter motor turns slowly like the battery is discharged , it could be a faulty winding. Some small engines use the same circuit running through the starter to the ignition system. If the starter motor is drawing too much juice it will cut back the power available to the ignition.
I had the same problem and it got progressively worse by shutting off sooner and sooner over one summer. I had the carburetor serviced, but still had the problem. The final solution was to replace the fuel shut off valve in the bottom of the carburetor. This part appeared to be ok, but engine heat buildup would make it fail--an inexpensive repair to a vexing problem! My sincere thanks to a local "back-yard" mechanic who gave me this tip.