I have a yard machines 42" cut riding mower, 14.5 hp ohv, when I cut grass and shut it off it won't start back till it cools down completely, I have tried every thing to figure it out, can someone help out please

Hi,
Usually that means a bad armature(ignition) that fails when the heat of the engine rises into it causing a failure. They cool and work, but usually get progressively worse.
Peace,
Clarke