It runs great. But the chain is a little rusty. I measure the chain wear and it looks like about 1/32 of an inch over 12 inches. So not much, right? But chains are cheap so I try a new chain. The new chain "clicks" at the chainring, especially under high torque. I can feel it in the pedals.
But the new chain "clicks" and that does not inspire confidence under high torque, and is annoying, so I put the rusty chain back on and all is well. What gives?
Possibly relevant: The new chain sat in the its package for at least 12 months. I rode maybe a mile or two with the new chain and the clicking before switching back to the old chain. The old and new chain are both KMC 8 speed chains.