This is one reason I grabbed my little CB175. It's a SOHC2, a half of a SOHC4; very similar mechanics but a bit more simple. I figured if I was going to learn on a beater bike, it may as well be similar albeit simpler. I got both the 175 & 550 service manuals, the 550 parts book, a couple of owner's manuals, all of the exploded diagrams for both and am looking for even more stuff if I can find 'em. Those books, this site and a good set of wrenches has been more than enough so far. While I'm not into a motor rebuild just yet, I'm learning fast on the other fun stuff like carbs, front end rebuild, etc. all while I get to keep riding my 550. Another reason is to have a ridiculously high milage commuter for the back-and-forth to work. And I really, really want to take the luggage rack off the 550.