Excuse me if I call them RD's. I was told they were "changers."

OK. I bought a 1989 Chorus group from a guy who rode it fairly often. It included 7-sp DT shifters with the blue insert, a Chorus RD, and a Regina 7-sp freewheel.

I put the freewheel onto my Record hub laced to a Sun wheel, no problem.
I mounted the shifters to the downtube of the bike, no problem, got the right # of clicks, no problem.
I mounted the FD and RD and the bike looks great. I adjusted the RD and the chain likes to jump from the outer cog to the 3rd cog. I did some adjusting, but since it runs from #3-#7 no problem, I left well enough alone. It shifts fine in friction mode (pull out the knurled knob, twist, etc).

The bike is still skipping the 2nd cog from the outside. I took it to a bike shop, and the mechanic said that the insert is incorrect, it should be a B model. I've looked for one, pretty hard to find part. Another mechanic said if I swap out the RD to an Athena, Victory, or Croce, pre-Ergo, it will work.

Since the gap between the outer cog and the next one in seems to be the problem, can the outer cog simply be taken off and a spacer put in, or is it more of a problem with the RD and/or spacer? I've not had a freewheel apart, and wouldn't want to mess it up.

I'm much more used to cassettes, and is it possible I can put a freehub on it and build a cassette with a little more gap between those two cogs to make it work?

I know the Syncro stuff was balky, and I'm sure the bike's rider (my relative) could make it work, but I'd like to remedy the problem.

Second issue: I have an extra one of those inserts and an extra set of 1st generation Ergos. If I put that insert into those Ergos somehow, would that create a 7-sp Ergo, given the right RD...it looks like the part numbers for the 8-speed inserts are the same, and I was wondering about moving "down..."

Thanks.

Oh man, you're really going to mess someone up in the future when those "7s Ergos" go back on the market. Just imagine the BF threads you'll generate.

I can only imagine....

It appears to me that the 8 speed Ergo's should work with the 7 speed RD. The 7 speed freewheels and the 8 speed cassettes have the same cog spacing (5 mm), and as long as you don't tell the RD that the cable is now attached to an Ergo mechanism at the other end, I think the same shift should result. Only thing, maybe the 7 speed RD can not make the full movement, but I think it will.
I used 8 speed Ergo's with 7 speed freewheels for quite some time, it worked flawlessly, but there the RD was matching.

It's a lot simpler to just buy a new Campy 11 speed group. I've got it on my winter/trainer bike. Yhr new ultrashift ergos are wonderful. A whole Athena group is only about $700.

I've always taken the opposite approach and dumped my 8, 9 and 10 speed parts soon after the latest is introduced. No retro stuff for me.

I don't find $700 simple in any way, really, but I'm C&V, so retro is what I do. Each to his own.
I suppose if you continually upgrade, you can offset the parts cost by selling the old, like trading cars.

$700 is more than every bike except my Kestrel Talon cost me, and that wasn't that much more.
Still, it's a relatively inexpensive hobby compared to many others.

I'm sorta looking for a mechanic's advice, but thanks, I appreciate the input.
(A C&V guy pretty much said the same thing, get a Centaur group and fuhgettaboutit)

I'm still going to search for an insert, or maybe a different RD. I'll likely end up with Ergos.

Robbie I'll look and see if I have one at the house tomorrow. but looking at my Campi book I think you need the green one for Chours (unless you have a wide freewheel then you need the black the "B" settings on the parrallelgram body). was the previous owner using Synchro or friction?

Previous owner was using index and made it work. He was very very good at adjusting his RD, and I'm not that good, and the bike's owner doesn't do it at all. His LBS says they'll adjust it if he gets the right RD/insert match.