After reading all the above posts, I assume that he ran out of fuel completely, refilled the tank with diesel, and now it won't start. It turns but puffs white smoke and doesn't fire. Correct? You didn't put gasoline in the tank instead of diesel did you? (I did. That's why I've <font color="orange">Exalted</font> myself.)
With that assumption, how long have you tried to start it? You can easily pull the fuel line off the fuel injector pump, turn on the key to ON (not Start), and you should see fuel coming out. It will fill a pop bottle in only a few seconds. If fuel is getting that far then you are almost there! Crank for 5 seconds (remember to pull the choke knob) and if it doesn't start it isn't a fuel problem.
That's a joke, son, about the choke knob. You don't have one. Check your carbureator belts and muffler bearings while you're waiting for a call from that online dating service.