That shaft that has come off, used to have a flared end that has worn down and now just falls off. I fixed mine by taking a dremel cutting disk to the end of the pole that comes off of the engine. first remove the shroud by losening the clamp. Then with a dremel, cut a slit lengthwise along the shaft to free the piece that the head goes into. once that piece is loose put the head back on it and with a hammer, flare out the end of the shaft so it can't slip out again. slide the whole thing into place. When you put the shroud back on, the clamp will keep everything in place. Good Luck
Stevo
May 2009