Originally Posted by Gonzo Bob
1) The smallest cog usually has a built-in spacer and those can't be reversed. Or did you mean the biggest cog (lowest gear)?
That's correct. However, I'm sure it isn't the big one that's skipping, those never skip.
Originally Posted by Gonzo Bob
2) I don't think tooth profile on Suntour cogs is exactly symmetrical but it would probably still work OK if reversed. If the biggest cog slides on instead of threading on, you can probably reverse it. On older Suntour FW bodies, I think all cogs thread on. For newer bodies, all cogs except the smallest slide on and the smallest one threads on.
The largest two SunTour sprockets are always splined. The teeth have a slightly beveled top, so reversing them is likely to cause a slight degradation in shifting, but they will fit either way.
Beyond that it gets very confusing. Back in the day, customizing SunTour freewheels was a regular thing, and good shops would have a complete sprocket board with all of the many permutations of sprockets and spacers. I've still got my old 12-38 7-speed kicking around somewhere. That one required a bit of blacksmithing to put together, always shifted like used food...
Sheldon "Cassettes Are SO Much Better!" Brown