Most important things are how much of a project do you want and how much are you prepared to spend. These bikes are all old and any can have issues, original bikes, customised, USA or UK models makes no difference whatsoever. They all rattle at idle but should reduce as soon as the revs rise a little. Avoid any smokers ideally, or really excessively noisy, but again depends on how much you’re spending and how much work you’re prepared to do. Are they mot’d runners or projects?.... If you dont know what to look for to avoid a real lemon, try to take somebody who does, thats the only real sensible advice.. Good luck, a nice 550 is a great bike!
