The basic platform was an upright, open seating position motorcycle powered by a carbureted, air-cooled engine wrapped in a steel-tube cradle-type frame, and at least one disc brake to bring it all to a stop. The simple design made motorcycling accessible to riders of all types and skill sets. UJMs were available in various displacements, and their ubiquity helped grow motorcycling in America during the 1970s and ‘80s.
Source: Motorcycle.com [1]
The term "Universal Japanese Motorcycle", or UJM, was coined in the mid-1970s by Cycle Magazine to describe a proliferation of similar Japanese standard motorcycles that became commonplace following Honda's 1969 introduction of its successful CB750. The CB750 became a rough template for subsequent designs from all three of the other major Japanese motorcycle manufacturers.[2][3] In 2011, the New York Times said lightning struck for Honda "with the 1969 CB 750, whose use of an inline 4-cylinder engine came to define the Universal Japanese Motorcycle."[4]
The UJM template featured a four-cylinder engine, standard riding position, carburetor for each cylinder, unit construction engine, disc front brake, conventional tubular cradle frame and telescopic front forks and twin-shock rear suspension. As the major Japanese motorcycle manufacturers, Honda, Kawasaki, Suzuki, and Yamaha, began replicating each other's designs, the UJM's created a homogeneity of form, function and quality. UJMs included such prominent models as the Honda CB500, the Kawasaki Z1, and the Suzuki GS750. Such machines had massive sales, and UJMs continued to be produced for more than a decade.
In 1976, Cycle described the new phenomenon, saying:
In the 2010 book, Sport Bikes, Hans Hetrick wrote that:
Subsequently, in the 1980s and 1990s, the Japanese manufacturers diversified their ranges, producing faired sportsbikes, race-replicas, dual-sport bikes and musclebikes.[7]