I had the same problem. After disassembling the engine, after the warrantee period expired and Sears was of no help, I found that the second piston ring had initially seized in the ring land of the piston and was scouring the engine bore generating enough heat that the piston would seize to the wall after the engine idled for a while or had stopped altogether, as the high heat generated was not quickly dissipated and the ring seized to the wall. After initially breaking the bond free, the engine would start again until the next use. The cycle kept repeating until there was a grove in the bore that would not allow full piston travel, even after the piston was freed. Each time the bond was broken by an attempt to start the engine more material was removed from the cylinder wall. I believe we are not alone with these problems of mysterious stopping and seizing of the engine. This scouring of the piston wall caused excessive blow by, which can create oil leakage.