Japanese Fours

Honda's CB750 fired the starting gun in 1969. Four cylinders, overhead cam, disc brake, electric start — everything the British bikes weren't. Within four years, Kawasaki answered with the Z1: bigger, faster, and arguably better-looking. The superbike arms race was on.

By the early '80s, the Japanese manufacturers had pushed the inline-four to places nobody expected. Honda turbocharged a V-twin. Suzuki handed Hans Muth a blank canvas and got the Katana. Kawasaki's GPZ900R broke 150 mph and launched the Ninja brand. Each generation made the previous one look quaint.

What makes these bikes collectible now isn't nostalgia — it's the realization that this was the golden era of motorcycle engineering. Every year brought a genuine leap forward. The inline-four became the default superbike engine, and these are the machines that made it so.