Kawasaki offered two smaller triples that followed the same general format established by the Mach III. The Mach I and II, or S1 and S2 shared a common bottom end and bore of 52.3mm and delivered their performance in a similar, exciting manner. The S1 in particular, was popular with younger British riders due to the 250cc restriction then placed on leaner riders. The styling reflected that of the larger models, although a front drum brake was employed.
1973 witnessed the introduction of the S3 400 as a replacement for the 350cc S2 or Mach II and for 1976 with the 250 S1 becoming KH250.