[Slam]

Note that each sprocket has 2 keyways and is stamped with an O and a U. Over and Under. You can't go wrong: keyways up, notch on sprocket aligned with timing mark. Have a look at the first pic posted in this thread.

What can happen is that rotating the tensioner can pull the bottom sprocket out of time. If so, you can gently slip it one tooth or so back I to time, or compensate by installing the lower out of time and pulling it into time as you rotate the eccentric tensioner.