I have a Kohler725-3065 engine on my mower that wont start. This is my first time looking at an engine. The engine will crank but will not turn over. If i put starter fluid in the air intake it will run for a second or two and then stop (likely burning the starter fluid only). I have pulled the carburetor and cleaned it out, replaced the spark plugs ( validated connection is good), replaced the fuel pump (verified its pushing gas to the carburetor), drained the fuel and put new gas in the tank, checked the oil levels. I am at a complete loss on what to do next here. Any suggestions on what to look at?