Please advise... I am thinking about buying a used yz400 or yz426. Can anyone give me their opinions on these bikes, both good and bad? What are they good at, what are they bad at? Anyone had problems with these bikes? What should I look out for on a used one that might be bad and expensive to fix? Any particular years that are better and/or more reliable? I'm not interested in anything after 2002 because I want the green sticker. Thanks for da' advise, B.