Originally Posted by
jonwvara
I'm a reasonably good bike mechanic. But so far, I've never had a freewheel apart to the level of cogs and spacers, though I've removed cogsets from bodies to clean and lubicate pawls and bearings.
I've been wanting a particular ultra-six freewheel setup for one of my bikes, but wide-range ultras are rare and very expensive. Corncobs, on the other hand, seem to be a lot easier to find. Would it be practical to buy a narrow-range ultra--say a 13-14-15-16-17-19--take the cogset apart and reassemble it with the cogs I want, taken from a couple of 5-speed Suntour freewheels? My understanding, quite possibly wrong, is that 5 and 6 speed New Winners, both ultra and regular, use the same cogs and bodies--that the only difference is the spacers. Also, that cogs from 5-speed Perfect or Pro-Compe freewheels can be installed on a New Winner body with ultra spacers.
Am I right or wrong about that? What kinds of frustrating problems am I letting myself in for?
I can't say anything about mixing and matching different SunTour freewheel cog styles, but my only experience with a wide-range Ultra was not good. My Trek 610 1984 originally came with a Helicomatic cogset in 14/28, and this was narrow-spaced, and did not shift with any precision. Even allowing for the ancient tooth design (not even a SunTour chamfer much less a smoothly grabby Shimano claw or a key-like Sachs ARIS), it was very poor. I've used the same Shimano 600/6207 derailleur with normally-spaced Reginas (similar ancient tooth), with much better results. YMMV especially with a Suntour tooth.
Another factor may be the use of a narrow chain with the narrow cog pitch. If you can do this with a 9-speed chain rather than a 5/6 speed, that might help you get good operation. With a chain who's gap is wider than the cog, the chain might over-shift just because it isn't narrow enough to sit squarely on the cog. I don't recall testing this before I sold the wheelset, however.
Good luck!
By the way, the Yellow Jersey site used to offer a SunTour freewheel mixing guide, with which one could cook up one's own. If it's still available for download, I bet that would help you.