I always thought a 'classic' bike is one that has a value (not nesccesarily in money terms) beyond its basic nuts, bolts and castings. That's why some say every Ducati is a classic as soon as it leaves the factory whilst some Jap bikes need a few years before they get past the new, second hand, bargain & hack stages. It takes a certain type of person to think of an old CZ as a 'classic' - maybe a similar type to owners of Austin Allegros and Morris Marinas - but if they're coveted for whatever reason, they must be.