I had a plane and engine (OS 40) that sat up one year. I took it out and put some run after oil in and got it freely moving. I then tried to start it and had problems. Looks like I am getting fuel to the carb from the tank, but the engine acts as if it is starving for fuel. When I add a little fuel to the carb intake it starts, runs 10 secs and stops. I have richened the high speed needle twice what it should be and gone back to almost lean. I did notice when I make adjustment on the fuel line the fuel migrates back to the tank. I am at a loss. Air leak maybe? This engine has about 20 flights on it.

Thanks