Radian Cafe Racer

Radian 600cc Cafe Racer by ZDR Custom Moto.

The YX600 Radian is a sport/standard motorcycle manufactured by the Yamaha Motor Company between the years of 1986-1990. 

The Radian came equipped with a slightly detuned version of Yamaha's 598cc, air-cooled, inline-4 which was used in the Yamaha FZ-600 Sport Motorcycle (grandfather of Yamaha's FZR series of performance bikes), and initially designed with 528cc for the 1981 XJ550 Seca and Maxim then in 1984 the bore, stroke and carburetor size were increased for the Yamaha XJ600/FJ600 sport bike. 

In 1986 the engine was fitted with smaller 550 style carburetors to fit between the frame rails in the Japanese FZ400 chassis and introduced as the FZ600 which was produced until 1988.

The YX600 Radian chassis received less high performance components than its race-bred relatives in order to make the machine more affordable for the general riding community. 

Some of these features included twin rear shock absorbers, rear drum brakes, and the lack of performance fairings, lending the motorcycle's appearance to the increasingly popular "Naked bike" styling at the time.

Info from Wikipedia