I'm hoping to make this aluminum frame conversion blog to be more like a how-to guide rather than the typical show-and-tell style. Since I've never done one of these, I'm not really qualified, but I've managed to do a variety of these types of projects (engine conversions, car restorations, etc) and have them come out farily good the first try, so I'll give it a shot. But you've been warned (the 'for dummies' refers to the author).
I picked up this 2002 CR125R that hade everything but the bottom end for $300 on craigs list. Apparently someone blew the engine and took it in for a rebuild, then managed to get divorced, broke and move before it was finish. (How fickel life is, eh?) It came with a new nickel plated FMF pipe and silencer as well as a cylinder and head, carb, and a variety of other parts. A few of these parts I sold on ebay for about $250, which I used to buy the new set of UFO plastics ($120) and the new SDS complete seat ($90), which you see in the pictures. The bike was in fairly good shape, except for needing a fork rebuild and new chain guide rubber and dust seals for the swing-arm. Overall, I'd say it was a pretty swingin' deal.