I'm really screwed now. I was mowing on a hill going up and down like always, but then my engine shook vigerously, and belched black smoke, died, and had alot of white smoke coming off the block under the head, but the gasket looks in tack all way round. It turns over fine without the plug in it, but with the plug, it turns over and then locks up, and the engine won't even sputter. I checked the carb, and the coil/pionts, and everything looks ok, I even had my dad who is very mechanicaly inclned look it over, and he couldnt figure it out... any Ideas?