I personally can't beleive the valves are having anything to do with your no start.It sounds to me that it is flooded. I'ld pull the plugs and see if they are gassy. If they are,leave them out for a day and let the engine dry out. Check your oil for excessive fuel also. Replace the plugs if flooded and check for a hot spark. Is there a resistor wire between to starter and the ignition? If its not flooded check for fuel starvation. Crank engine while gassing with carb spray. If it fires, no fuel. You can really mess up valves and still get something (unless you bent them). Keep us informed - Scott (new to this forum stuff)
