BACKGROUND NOTE: The bike is a 1992 Univega MTB that originally came with 6-speed SIS with a triple chainring. I removed the SIS shifter when it broke, and went with a friction shifter. The bike is used as an all-purpose commuter/errands bike; I was having no problems with the "old-tech" setup other than a worn chain, and I have no plans to change the friction shifter on an old bike.
6-speed Sunrace Freewheel (straight-cut, 14-28); 6-speed chain (don't know the type).
7-speed DNP Epoch freewheel (beveled or ramped cut cogs, 11,13,15,18,21,24,32); KMC Z50 chain (1/2" x 3/32", 6-7 speed). The KMC chain box says "Indexed."
BOTH SETUPS USE:
Long-cage rear derailleur (Shimano Exage), triple chainring (28,38,48; Shimano Alivio, 18-24 months), and friction shifters.
THE REASON for the change:
chain wear and skipping, wanting two faster cogs and a lower hill-climber cog. The new chain was adjusted for length using the chain adjustment equation on Parktools web site. After installing the chain, I doubled-checked and eliminated any chain kinking. The rear derailleur is adjusted and shifting well with the new setup. When I re-installed the rear wheel, I placed a thin washer between the right-side axle nut and the dropout for chain clearance on the 11-cog but it might not be necessary.
The new chain is intermittently skipping in a "skip-forward" or half-shift" motion; less so when riding casually, more so when riding under load; less so on the 48-tooth chainring, appears to be more so on the smaller chain rings.
What's wrong with my new setup?