I have a Walker Model C with a Kohler 16 HP engine. The mower was working fine until a couple of days ago. The mower would turn over, but would not start. I took the air filter off and cleaned it and also cleaned the carb. with an air compressor. I then sprayed with Quick Start and the mower cranked and I let it run about 15 minutes with no problem. The next day I went to use it. I tried to crank it before I left and it cranked up and I shut it right back off thinking everything was fine. I then proceeded to a job. The mower cranked and I was able to drive off the trailer before it stopped running. It would not recrank. I got more Quick Start, but it still would not crank. The fuel filter looks fine. Any suggestions?