I'm thinking about buying a Vulcan (or just have) and don't know if there is warranty left or whether the bike was ever affected by any recalls.
Not a problem. Kawasaki's website has all that information and all you need is the serial number which may be printed on the registration (depending on state) and is definitely stamped into the steering head of the motorcycle.
If you're just looking for general recall information maybe for a particular model or year there are two places to go.The best (but most difficult to navigate) of all, the National Highway Traffic Safety Administration Website. There is a recalls page that covers virtually every make, model and year of every motor vehicle ever produced.