I had the same problem with an OS 91 in my U-Can-Do except mine would usually start (by hand) but would not run at full throttle until tank was about half empty. I installed a cline regulator and it now runs at all throttle settings but I have to start it with an electric starter. It will not draw fuel through the regulator by choking the engine so I have to put a starter on it. Go figure. Well I guess that is better than the flooding problem.