I need help from the big boys. I have a 6.5 hp Briggs motor when you start it up cold it will start right up. when you run it for 30 min or longer and shut it off it won't start. But when you let it cool down it will start right up. Its been in thge shop 6x they checked the valves , new carburator and said they went through it they even had a briggs rep down for this. know today it did the same thing. It seems somthing to do with it getting warm and won't start. Any ideas? Its in the shop today it's in it's new home.