The crank is rubbing on the chain guard. What can I do?
If the crank arm rubs repeatedly on the chain guard, it means your chain guard is not correctly installed. This is easy to solve:
1. Loosen the two screws that mount the white inner part of the chain guard to the frame (on the chain stays, close to your bottom bracket).
2. Move the whole chain guard a little closer towards the frame.
3. Once in position and not rubbing, re-tighten the two screws by feel.