I'm fixing this bike one piece at a time. And when I say "I," I mean you.
So I had to get the crank out so I could check out the bottom bracket because it sounded and felt pretty gritty. Well of course it did. It was chock full of grit. The focus on these isn't great, but trust me, there was a nice layer of particles on the center of the crank, and a matching pile of debris in the bottom of the bracket.
This is probably the first time I've ever actually serviced the bottom bracket of a bike, so I was surprised, given that I thought it should be kept as clean as possible, to find that the seat tube seems to go right into the bottom bracket. Is that normal? Is that necessary? Can I plug up that hole at the bracket side to prevent more crap from dropping in? I'm sure there's a bit of rust in the seat tube. I sprayed some frame saver in there, but without actually being able to clean out that tube first, there's no telling how much good the frame saver will be. And, being that this is a folder of sorts, one of the folding steps involves taking the seat stem out of the tube and putting in another piece. The result being that the seat tube sees a fair amount of action, much moreso than a normal bike where you adjust your seat and then forget about it.