I let a friend borrow my bike this week for a ride and somehow he bent the rear derailleur cage and now the the chain skips in when in 6th gear due to the jockey pulleys not matching up with the cog.

I need the bike today and want to know if I can use a modern 7/8 speed derailleur on this bike. The old derailleur is a Shimano 600 81 vintage with friction shifting with a 6 speed cog? Also can you recommend a deraileur?

Thanks

Have you tried bending the cage back into shape?
I don't have one in front of me but I believe that cage is steel.

I did try to bend it back but just can't get it right, and it is pretty worn.....

friction shift? you can pretty much use whatever you want

hmm you'd better buy new one

Even an almost totally shagged rear derailleur will work fine with friction shifting, as long as it's able to cover its range with the jockey wheels somewhere close to properly aligned.

You may need one in slightly better nick if you happen to be friction shifting 9 or 10spd, but that seems a bit unlikely

Turns out the Derailleur was trashed as I suspected but the hanger was fine. I replaced the derailleur with this one and now is shifting smooth as butter, and no more skip. I know it not a vintage rd but that's all that was available and I want to ride so on it went.... I have to say, the shifting is much more responsive than with the old derailleur.