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. Throughout the 1980s the motorcycle industry gradually went from building a few basic but versatile models designed to work well in many roles, to offering many more specialized machines designed to excel in particular niches. These included racing and performance street riding, touring, motocross racing, enduro and recreational off-road riding, and cruising. Yamaha branched out from the relatively small number of UJMs (Universal Japanese Motorcycle) at the start of the decade to a much larger set of offerings in several clearly defined markets at the end of the decade. The XV750 of 1981 featured an air-cooled V-twin four-stroke engine and cruiser styling, and was one of the first Japanese cruiser style motorcycles. By the end of the 1980s Yamaha had offered dozens of cruiser styled bikes in a variety of displacements and engine configurations. The RZV500 was one of the first "repli-racers", a near copy of Kenny Roberts competition GP bike, it featured a liquid-cooled two-stroke motor of 500cc displacement in a V4 configuration, along with a perimeter frame and full fairing. A more popular and practical high-performance model for the street was introduced in 1985, the FZ750. It was an innovative 750cc four-stroke inline four cylinder model. It was the first motorcycle to feature a five-valve cylinder head, something Yamaha became well known for. It also featured a cylinder block canted forward at 45 degrees, and a box-section steel perimeter frame. Production of the FZ continued until 1991. Another bike that was performance-oriented was the Yamaha RX-Z, introduced in 1985 as a two-stroke naked sport bike, related to the Yamaha RX-135 and Yamaha RD-135, borrowing its chassis and platform. Originally equipped with a five speed transmission and a solid front disc brake rotor with rear drum brakes, it was popular in Malaysia and Singapore. After a few years on the market, the engine was upgraded with the installation of a six-speed transmission, together with a newer instrument panel and handlebar switches, as well as a cross-drilled front disc brake rotor, while the rear remained with the drum brakes. The design was unchanged until it was updated in 2004, with the rear lights