I wanted to follow up on my year/model comparison info in case anyone is interested. I have found that both the Kawasaki KX500 Factory service manuals & Chilton service manual have good year to year change info on KX500s. The Chilton manual is in some ways better as it covers the full KX500 history from 1983 to 2004 where as the Kawasaki manual covers from 1988 to 2004. (Pre 1988 Kawasaki manuals exist separately from the more recent 1988- version.) These manuals cover everything from port & ignition timing changes to gear ratios & everything in between. They are great resources to see how the KX500 model changed through the years.