I need some help diagnosing some derailleur problems if you can. I’m posting this in the mechanics area as well as classic and vintage.

I recently changed out the rear derailleur on my 25 year old Cannondale racing frame. I’ve had a 13-24 Suntour New Winner Freewheel on there with a Suntour Suberbe derailleur since the bike was built. (The front has been a Sakae triple with a 34-42-52 since about 1990). I recently decided to throw a bigger freewheel on the back in a concession to age and weight, (59 and 230 respectively) I’m hoping to shed the extra pounds by next year, at which time I’ll go back to the old setup.

I have a pretty good parts bin, and had no trouble locating a 13-32 New Winner Freewheel in good shape, along with a Cyclone MK-II long cage derailleur. I also managed to find a brand new, NOS Sedisport chain in the original packaging. I put the whole thing together, taking three links out of the chain to fit the new drivetrain. Everything sounds perfect, doesn’t it?

Unfortunately, my first test ride the other day was a dismal failure. The derailleur shifted like crap and was noisy as hell. I was really surprised at this, since I’ve done this kind of modification many times. The chain often overshot the sprocket I was looking for, (I remember this being a not unusual problem with New Winners, since the spacing is fairly narrow), and I even managed to throw the chain to the inside of the freewheel once or twice. (Yes, I do know about the adjusting screws)!

I put the bike back on the workstand today, and took a good hard look at the new setup. I realized that the pulleys on the old Cyclone MK-II were fairly worn, and the brand new chain wasn’t seating correctly. The jockey pulley seemed worse off then the tension pulley, and it appeared that the chain was coming off the jockey pulley and clattering like hell.

Back to the parts bin, and there I find a mint condition Cyclone MK-II short cage derailleur with perfectly new pulleys. I remember taking this particular derailleur off my wife’s new Nishiki International in1983, when I changed out her freewheel for a bigger one. I took the pulleys off the short cage derailleur and swapped them for the worn out pulleys on the long cage derailleur. Now I have a good condition long cage Cyclone II derailleur, with brand new pulleys, a brand new Sedisport chain, and a good condition 13-32 New Winner freewheel.

Back out for a test ride, and I’m still getting a lot of clattering. Back on the rack, and it seems that now it’s the tension pulley that’s making a lot of noise .The chain and pulley are having trouble staying synchronized, and the chain is jumping off the pulley a little.

I have two theories, but I’d appreciate some expert help if I can get it. My first theory is that I need to take another link or two out of the chain. My second theory is that the derailleur long cage might be bent after two and a half decades in the parts bin.

What do you guys think?

Thanks, in advance, for your help