Hi! I'm new here, and wanted to know if this rattle is common, and if there's anything that can be done about it? It doesn't sound like much in the video, but when riding over rough terrain it's really noticeable! Here's a little video showing it:
Theres a whole forum section for Shimano motors.
Click -=> Shimano <=- Click
You'll probably get better answers in there, or may even find a post that answers your question.