I had the same problem with my Craftsman LT1000 tractor. It wouldn't turn over. I purchased a new battery, used it all day and the next time I went to start it, same issue. Took the battery back and they tested. Perfect battery. So I started looking into other possibilities. I noticed I smelled gas when this happened. It seemed like the engine was locked up. I took the air filter off and clamped the gas line and waited a while. Boom, it started. So I replaced the gas filter and installed a shut off valve on the gas line. As long as I remember to shut the gas off after using the tractor all day, I don't have this problem. If I forget to shut the gas off, it locks up. Some kind of vapor lock. Hope this helps.