By 1980 the combination of consumer preference and environmental regulation made four strokes increasingly popular. Suzuki ended production of their GT two stroke series, including the flagship water-cooled two-stroke 750cc GT-750 in 1977. Kawasaki, who had considerable success throughout the 1970s with their two-stroke triples of 250cc, 350cc, 500cc and 750cc ended production of road-going two strokes in 1980. Yamaha bucked this trend and continued to refine and sell two-strokes for the street into the 1980s. These bikes were performance oriented, water-cooled twin cylinder machines, designed to achieve excellent performance taking advantage of the lower weight of two strokes. The RZ-250 of 1980 was the progenitor of this series. The RZ-350, the largest displacement model, was a popular hot-rod bike of the 1980s and continued to be sold in some countries into the early 1990s.