There's a 1998 Burly Rumba available locally. The price is right if the parts are in good shape. I do have a question on the bottom bracket though. I've read that Burley used to use a proprietary system.
Does anyone know if this bike had a proprietary bottom bracket? If so, what is off standard? Is it the shell size/ threading?
Is it pretty much a pain to change a bottom bracket or adjust the tension, or is it no big deal?
I have a 94 Bossa Nova that has the proprietary rear bottom bracket. If yours is the same, the bottom bracket consists of a set of standard, easy to find bearings on each side press fit onto a spindle and the whole assembly is press fit into the bottom bracket shell. It is also held in by retainer clips on each side. I destroyed the bearings when taking it apart to have my frame powder coated and can give you directions on the right way to get it apart. To rebuild it cost me $7. Somepne else needs to let you know if they are the same or post a picture if you can.
This site has specs listed. http://www.gtgtandems.com/specs/burleyspecs.html
For Rumba it says:
1998-1999: precision sealed bearings oversized rear.
2000-1: burley sealed cartridge
2002: truvativ (others have shimano, etc.) In this year, it looks that they are all generic.
So, are these bearings just like a a sealed cartridge wheel bearing? I'm now picturing bearings like these: http://www.endurobearings.com/
that are press fit between a shell and the axel. The shell would then go into the eccentric piece that either screws or is pressed into the bike frame.
If I understand it right, the whole purpose was to have a wide (82mm) bottom bracket shell.
I have no pics, because locally means 3 hours of driving round trip. If the whole thing is going to lead to a royal pita down the road, I'll skip the trip.
On my bike they are like the bearings you showed the link to. Minus lots of water or if you want to disassemble for painting, these types of bearings should last a long time as the load is low and the RPM's really low compared to what they are designed for. Mine are just pressed in. This is the back. The front eccentric is just a machined piece of aluminum with the bearings pressed in and the axle going through that is held in place by set screws. I think this is a straight forward simple bottom bracket that requires no maintenance and cheap to rebuild if necessary.