I have been fixing up a Northrock XC6 bicycle.
Chain clunk when trying to start moving. It feels like the chain is slipping. It only happens under load, I cannot get the same symptom by running the wheel by itself. This makes it impossible to get started. However, the same problem does not occur when at higher speeds.
I just installed a new derailleur, new chain, and new pedals. I needed a new derailluer because a similar problm happened and bent the old one and broke the chain.
What is wrong with my bike? Thanks!