I picked up a '76 CB 550 the other day. The guy on craigslist said it was highway ready, but me and my buddy decided to take the van down anyway. Good thing as the tires were dry-rotted, the electrics were iffy, and the chain was rusted. He asked for $850, I talked him down to $670 (based on the aforementioned flaws and lack of current inspection).
So I got it home, replace the blinker (flasher part), battery, sprayed out the carbs (because it wouldn't idle well) and she's running like a dream, sorta.
There are a few problems with it:
1. The throttle sticks open and won't snap back. After lots of work and searching here, I decided to disconnect the throttle return cable and let the spring do its job. I tried all the tricks except for actually replacing the cable, but that's scheduled for the future.
2. Already took care of the stalling @ idle with either new battery or spraying out the carbs
3. The tires are dry-rotting and need replacing. Already working on that one
4. Chain is rusty and I probably should replace it. Is it recommended to do the sprockets too? I heard that somewhere.
5. I learned of this one after taking it out for the first ride: While engine braking after high-ish RPMs there's a grinding type noise that comes and goes from the motor. Its very difficult to describe.
Overall I really like this bike. I bought it to tool around the city and commute to/from work on sunny days that I don't want to cycle--its about 3 miles. That and free parking at work for motorcycles! I've previously owned a '02 CBR600F4i, but I laid it down and sold it. I'll do better this time.
Here's some pics, too. Its got the original (I assume) 4-into-4 exhaust in great condition. The bike is in fantastic condition overall for a bike that's 32 years old!