As a previous owner of a '79 CX 500, I can say they are the ugliest bike ever made! (This from a Rocket III owner..lol) However, they are much more powerful than their 500cc's would lead you to believe. They are almost maintenance free, with push rods and hydraulic lifters, and they really have a nice sound to them as well! I actually miss that little bike. The only common problem I know of for CX500s, is the alternators. I never experienced this problem though. The motor has to come out to replace the alternator.
I bought mine for $500 bucks from a co-worker in 1998. I had warned him for months that he needed new tires, and he ended up wrecking the bike in a rain storm. Luckily, it had bags and a vetter fairing, and they took all the damage. The bike itself survived well. It was an ugly brown color. I removed touring crap, stripped the paint and painted it a nice shade of blue, put a nice chrome headlight and front turn signals on it. It was a fun, and suprisingly fast little bike! Yes, it would be a fun cafe' project!