The 500cc open class was the fastest thing in American motocross — and the AMA quietly stopped running it. The bikes stayed on sale for another eleven years. The reason the pros walked away is in the engine. . . . #OneLungRacing #2Stroke #KX500 #CR500 #Motocross #OpenClass #AMAMotocross #TwoStroke #DirtBike #500cc #MXHistory #VintageMotocross #Kawasaki #Honda #Powerband #BigBore #MotocrossHistory #DirtBikeLife #MX #Enduro #RacingHistory #MotorcycleHistory #90sMX #80sMX