After completing the ignition rotor and cylinder head nut bulletins, and checking my valves, I put my bike back together. When I fire it up, it idles for a few seconds, then backfires and stalls. I seem to have screwed up the timing. I was very careful to do the bulletins one bolt/nut at a time. I carefully checked the cams to make sure I reinstalled them properly according to the timing marks on the camshaft gears. Any thoughts on where to look next?