Bicycle Mechanics - Bad shifting on Suntour Accushift

I bought a beater bike for doodling around town. I cleaned off the years' accretions of crud. Yes, there was a bike under there, a Raliegh hybrid with Suntour Accushift (indexed) derailleurs.

I can't get the indexing on the rear derailleur right. The high and low stops are set correctly and I have read all about turning the barrel bolt to set the indexing. When I shift down, it doesn't shift, but just grinds away. I usually have to shift down two gears, and then back up one--i.e. when I shift down two, it goes two, but trying to go one doesn't work. Upshifts are pretty reliable.

The chain is still reasonably close to its proper length, and the cogs are not excessively worn. The one thing I have not yet tried is replacing the cables.

Also, the shift lever has settings for "index" and "friction", but I cannot get it to do anything but "index."

Any advice?

Cheers,
Jamie

Sounds like a cable problem.

As I remember, there is a tension-screw on top of the shifter, back that off a tiny bit and see if that allows you to shift to friction. You might also put a DROP of lubricant in them.

Maybe the derailleur hanger is misaligned? Try standing the bike against a wall and looking at the rear derailleur cage from behind. If it doesn't look like it's parallel to the plane of the bike's frame, then either the derailleur hanger is misaligned or the derailleur's bent (or both).

In cases of a misaligned hanger, you can do a pretty good job of straightening it with an adjustable wrench to bend the hanger, then use the derailleur as a gauge (unless it's bent). There are specific tools for that, and hopefully the LBS has one if you want it done the official way.

New cables and housings might help, as you say, particularly if the old ones are corroded (Suntour cables seem prone to developing powdery white corrosion). You can slide the housings down the cables and check their condition, and perhaps oil them if they don't look too bad.