Unless you have the original title information, and
if the state in which the bike was originally titled required engine numbers on titles, you probably will never know for sure the exact engine number that came with the bike. The engine and frame numbers on KZ650-B1 models were an exact match for the first 50 or so bikes, but after that they drifted apart. However, there are specific ranges of engine numbers that match frame numbers, so if your engine falls within the range it may very well be the original engine. Here's where you can look up that info. Ed
models.kz650.info/index.htm
