I put two flights on my YS63 today and the engine ran perfect for both flights. After starting the engine for the third flight of the day the engine seemed to load up and then quit. I thought right away that the glow plug had went bad but I started it up again and as soon as I took the glow driver off the engine quit. I replaced the plug with an OS type F, hooked the glow driver up and gave the prop a couple flips and it fired up but for the first time ever with this engine it started and was running backwards. I quickly stopped it and then started it again and it started backwards again. Each time it started backwards it sprayed fuel everywhere, after stopping the engine each time quite a bit of fuel ran out of the carb. After the second time of it starting backwards I got out my electric starter and used it to start the engine but it still seemed to be loading up and wouldn't stay running more than a few seconds without the glow driver and it still seemed to be leaking allot of fuel out the carb after it shut off. It seems pretty clear that the fuel leaking out the carb is the cause of the engine loading up and quitting but my questions are:

What would cause the fuel to be leaking out the carb?
Did I hurt something when the engine started backwards?