I asked for help in the mechanics section a few days ago and didn't really get anywhere. I am hoping you folks over here know more about the idiosyncrasies of a vintage bike.
I bought a '74 Motobecane Grand Record a few weeks ago. Beautiful bike (pictures forthcoming) It has a Campy NR triple with a Campy Rally derailer. The freewheel was a '72 Suntour 14 to 34 5 speed. Suntour barcon shifters.
I took apart everything and cleaned & greased.
I took it out for its maiden voyage and the chain skipped. It was the original chain. I measured and it was stretched, so I replaced with a KMC Z 5 to 7 speed chain and made it the same length as the original. I made sure there were no stiff links. I saw no noticeable wear on the freewheel or chain rings so I left those alone. It rode better but the chain skipped under load in 4th & 5th gear in all 3 rings. I had the freewheel replaced with a 14 to 28 Shimano cheapo. I rode it for a few days and didn't notice any skips (maybe it was still in process of tightening up?). Now the skips under load are back in 4th & 5th.
When I had the freewheel replaced at the LBS, I asked about the chain length because I was going from a 34 down to a 28. He checked the combinations and said that it was a little long, but it was in the low/low combos that I shouldn't be riding in anyway. I removed a couple links after it started skipping again and it hasn't helped.
My chain rings don't look worn and since they are 74 NR, I'd rather not replace. Also, if they were worn, I'd expect it to skip more in the middle ring vs. big ring, but I can make it skip in all 3 rings. Could there be issues with my Rally derailer (which is beautiful btw. and I'd really like to keep)? Could low chain tension be causing this?
Any pointers from ya'll who have been there done that?
Here is a pic of my front chainrings and the original Suntour freewheel.