A couple of months ago I bought a 1986-vintage Peugeot Orient Express at a garage sale. I had my local bike shop put new tires & tubes on it, and since then I've been riding it relatively trouble-free.
A week or so back, I was riding it and the freewheel stopped working properly. The pedals would spin in the forward direction, but the freewheel wasn't engaging, so the rear wheel would not spin. I got it home, lubed the freewheel, and everything seemed to be fine.
This morning, when I shifted the chain to the smallest rear cog, at first everything seemed to be fine, but all of a sudden, the chain started skipping. I don't know if that is the proper expression, but the normally smooth passage of the chain over the smallest cog became jerky and rough. This didn't happen in other gears, so I shifted to a lower gear and brought it home. The chain seems to be well-lubed; nothing looks to be bent, and when I lift up the bike (so the rear wheel can spin without any weight on it) and rotate the pedals with the chain on the small rear cog, it seems to operate smoothly and normally. Yet when I ride the bike, I get the same skip/jerky chain action. When this happens, the arm on the derailer is moving back and forth.
I don't know if the two problems are related, but I would appreciate any insight/advice.