not many changes over the years I have an 01 and my buddy's is an 87
his motor is black, mine is silver. His has a paper top end gasket, mine has a steel one. His sproket is held on by a locknut and washer, mine is a circlip. He has a two way powervalve, mine has a three stage.
I'm not sure of the cuttoff years but I think it's from 86-87
88-95 and 95 to 03 changes were made....
somebody correct me if I'm wrong
If all else fails use the numbers off the engine