The clunking seemed to come from the rear and could be felt every time I coasted for a bit and then started pedaling again. Kinda felt like driveline slap. The bike was a demo, so it was probably used and abused. Also, the battery was almost dead, so the motor was not putting out anywhere near peak power/torque. I had a chance to ride the bike again with a fully charged battery, but declined because I didn't like the bike that much.