I have a small 33cc two stroke that will only run if I put some fuel in the sparkplug hole directly on the piston. Dies as soon as this fuel is gone. I have replaced fuel filter in tank, fuel lines, cleaned the carburetor, installed new plug, tested cylinder pressure (120 psi), checked crankcase seals and even tried a New carburetor. Cyclinder leak test holds its pressure. I have examined intake and exhaust ports and all are normal. There is no reason for this engine not to run. What have I missed?