Manual, Z50 K1-K4, Hardtail through the K4 Softail. Parts Manual for the Hardtail through the K4 Softtail Z50. This manual will have exploded views or break downs of your complete bike, showing all of the individual parts as well as the Honda part numbers for all of these pieces. It covers all of the models listed, KO (1968) through the K4 model (1973).