Chain falls off upper pulley when backpedalling I just found out that indexed shifters required mated cassettes, and I am using the rear wheel and cassette from an indexed setup with a non-indexed rear derailleur.  I noticed backpedalling sometimes results in the upper pulley going askew as pictured, and always happens during an upshift.  I never had this problem with my indexed setup.

I have two questions:


I understand simultaneously backpedalling and upshifting is bad, but does the chain falling off the pulley the expected outcome of doing that?
Is it okay to use a cassette from an indexed shifter from a 1990 shimano 105 with a non-indexed shifter like a 1996 suntour cyclone.


I've read the the very similar problem and I included a shot of the teeth of the upper pulley in case that might be the problem.  Also, when the chain does go askew, I don't really feel the difference (I'm not a particularly distinguishing rider).
Yes, chain falling off the pulley is expected. When you backpedal, the chain is moving from rear cog to pulley and you are moving the pulley away from the incoming chain. Don't do that. The pulley is by the way really worn, replacing it might improve things.
It should work, but you need to be very precise with the shifter.