While Kawasaki was working to "make the H1 acceptable in civilized society", they also released the delayed inline-four four-stroke, the Z1, in 1972, which had adequate brakes and handling, comfortable seating, and did not guzzle fuel. The sales success of the Z1 demonstrated that there were more buyers for higher-priced but less obnoxious sport bikes, than buyers who would accept numerous compromises for an extremely fast motorcycle at a low price. More stringent noise and pollution regulations also contributed to the end of the H1 500 production, whose final year was 1976.