Originally Posted by Tom Stormcrowe

If it's a freewheel then spacing between the gear cogs will be equidistant, and Suntour isn't indexed for shifters, that I remember, so it doesn't matter. Your shifters are friction shifters, correct? As The ARS put it, just change the freewheel out rather than trying to rebuild it. He could have put it a bit more gently, but he's correct as far as what to do.

Originally Posted by bradtx

Pibber, Replace the freewheel and chain for the best results.

Brad

Originally Posted by cny-bikeman

The chain won't break but allowing one to wear to the other may not occur or will take a very long time. Measure the chain (and while you are at it learn about chain/cog wear). If needed replace it, and then if needed replace the freewheel as well.

Originally Posted by Asi

I'd suggest a new freewheel and a new chain to go with it. For 6speed is quite cheap.

Another approach is if you have more freewheels at hand. The cogs on the freewheels are threaded onto the one way mechanism and you can unthread them and mix and match your own cassette - but it's such a hassle that may not worth it, and the threads on the freewheel cogs are not standard.. at 6speed you have lots of brands like Atom, regina, suntour, shimano, etc.

But given a larger stash of freewheels to have all the correct part, mix and match sprockets onto them was common practice in the 80-90's - beware that it's a PITA to remove the cogs from the freewheel, you need a large bench vise and a very large chain whip and a hammer of your choice

http://sheldonbrown.com/freewheels.html