Currently, when I try to start the tractor, it kicks back. I am using the hand crank, and normally it would be 1 or 2 tries and fires right up. Now, it almost pulls my arm out of socket when it happens. Leading up to this, I had my son sickle bar mowing. We were late in the season, so weeds were high, and we were 3/4 done. The tractor shut off on him while mowing, and I haven't been able to start it since. My sense is that the timing is off, but I am not sure where to start checking. I have spark, and have checked some of the simple items. Looking for suggestions but need to start slow. I'm not that familiar with the tractor. I do have a manual.