I have an '94 burley tandem with Sansin hub and Suntour 7 speed cassette labeled APII. Broke a spoke on the cassette side. I know I need to use double chain whips to remove the locking cogs to remove the cassette. My question is are the splines on the hub compatible with any other cassette or are they specific to the Suntour cassette? I am thinking down the road, when and if the cassette dies what to do.
'''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
AFAIK, Sun Tour cassette cogs are NOT compatible with Shimano cassette cogs and the freehub bodies can't be interchanged either. When your cassette needs to be replaced you will either have to get lucky enough to find an NOS original Sun Tour or you will need a new rear hub.
The original Sun Tour company (aka Maeda Iron Works) has been out of business for many years. The current products sold under the "Sun Tour" name are made by a completely different company that only bought the rights to the name.
Last question: is the topmost (smallest) sprocket threaded or splined like all the others? If it's splined like all the other sprockets (we will hope so), then you have a Hyperglide cassette and hub. So... the splines are not specific, the only thing you have to keep in mind is that you can only use a 7-speed Hyperglade cassette to replace yours. Any 7sp suntour (I just have a 7sp suntour cassette in my kitchen right now (don't ask why)) will work, as well as any Shimano HG. Just a few examples
The last cog only is threaded, the other 6 are splined.
If the last "cog" (actually, sprocket) is threaded, then you have an Ultraglide, old type cassette, and the HG won't fit. You're out of luck. You would either have to replace the UG UG hub body with a HG hub body, or try to find an UG cassette, which doesn't seem easy. It's easier to find old 7-speed freewheels.