You've most likely hit the nail on the head. The rear derailleur is out of alignment, just a little. I saw this when I set it up, but was very reluctant to take a shifter to it to straighten it. I think it does sit flat, on the bench, but the der. pivot is worn, to that it is skewed outwards at the front when mounted.
I thought that a little misalignment would not make much difference - apparently it does.
The gear change, however, is as smooth as silk; the only negative is the longer travel of the Huret d/t shift lever, just a matter of getting used to the longer throw.
It's a good excuse for me to make up a 'hanger straightener' tool. I'll have to check the thread first.
> Perhaps the rear derailler is out of alignment or bent. Had similar
> problem. I took it to a LBS and they aligned the RD and cured the problem.
> The bike fell down on the RD side a few times over the years which accounted
> for the misalignment.
> John Hawrylak
> Woodstown NJ
> ----- Original Message -----
> From: "Paul Aslanides"
> > Hi All,
> > I've just rebuilt my recently-acquired Claud Butler,
> > 'Electron' Super Five model. It's a lovely, smooth ride, too.
> > The problem is that when I change gear, the chain also
> > derails off the chainwheel, almost every time.