Apparently....air was not a given...It takes 4 things to get an engine to run: Air, Fuel, Compression, and Ignition. Air is a given and you appear to have ignition. So that leaves fuel and compression. Since you can get it to run cold, compression is probably ok, though if the valves are too tight they may cause issues once warmed up. So, how is the fuel supply? Have you checked the gas cap? The fuel filters?