How Kawasaki Fixed The H2's 'Widowmaker' Reputation

The 1970s was an era when motorcycle manufacturers, freshly drunk on the explosion of the superbike market, decided the best way to stay on top was simply to offer an ungodly amount of horsepower, while completely ignoring whether the motorcycle's chassis or the rider could even handle it. Honda delivered the smooth, reliable, and completely civilized CB750 to the world, but Kawasaki looked at that motorcycle and chose violence.

In 1972, the brand dropped the Mach IV H2 750. It featured a 748-cubic-centimeter air-cooled, two-stroke triple engine that delivered 74 horsepower. While the numbers might not feel like much, the H2 beat the fastest motorcycles of the '70s when it came to quarter-mile times, crossing the line in under 12 seconds. Due to its performance, it soon came to be known as "The Widowmaker." It's an ominous name, but still not quite as cool as the Suzuki "Whispering Death" RG 500 — the most dangerous motorcycle ever sold.

To understand why the early H2 wanted to kill you, you have to understand how a large two-stroke engine delivers power. Unlike a linear four-stroke engine, an aggressive two-stroke engine relies heavily on exhaust tuning. Below 4,000 rpm, the H2 was relatively docile. But the moment the rev needle swung past that, it offered a violent surge of acceleration as the torque practically doubled in an instant. If you were mid-corner when the bike reached its powerband, the sudden surge of torque  would break rear wheel traction or twist the frame into a terrifying high-speed wobble. Compounding this effect was the chassis geometry -– a light front end, a short wheelbase, and a chassis that flexed in corners would help routinely spit riders off, cementing the H2's lethal folklore.

Kawasaki knew that the H2's decent success on the market hid a potential PR disaster. So, for the 1974 model year, the brand's engineers went to work taming the motorcycle. They didn't fundamentally redesign the engine, but they worked on how the rest of the motorcycle behaved. First, they attacked the suspension geometry. Kawasaki lengthened the swingarm, stretching the wheelbase, which helped keep the front tire firmly planted on the asphalt. They also revised the steering rake from a conservative 28 degrees to a sharper 26.5 degrees, pairing it with 4.09 inches of trail to give the motorcycle high-speed stability.

Then it was the engine's turn. By subtly altering the port timing and reworking the exhaust system, Kawasaki engineers smoothed out that terrifying, almost exponential torque curve. Kawasaki shaved a few peak horsepower off the top end –- dropping the output to 71 hp  in 1974, and 70 hp for the final 1975 model year. However, this drop in straight line acceleration bragging rights helped make the H2 a more friendly, rideable motorcycle. The engine's low-end manners improved, making the transition into the powerband more predictable. The resulting 1974 and 1975 models were considered safer and better-balanced. Taming the H2, however, did take away some of its scary legendary status. And despite Kawasaki sorting out the handling, the end for the Mark IV H2 was near.

While Kawasaki engineered the "Widowmaker" flaws out of the H2 chassis, they couldn't engineer their way around a changing market. The 1970s brought an oil crisis, tightening safety standards, and the blow of the US Clean Air Act. Big two-strokes were dirty, loud, and thirsty. In fact, early H2s left a trail of thick blue smoke because their variable delivery oil pumps were unnecessarily left at maximum settings by dealers, and two-stroke engines are so environmentally unfriendly by nature. Consequently, by 1975, road-going two-stroke engines were almost dead. Kawasaki halted further two-stroke development, shifting its engineering resources toward four-stroke engines instead.

The H2 was replaced by the legendary Kawasaki Z1 900 –- a sophisticated world-beating, four-cylinder superbike that proved performance didn't have to feel like a near-death experience. However, those original, unhinged 1972 H2 models are still highly sought after by motorcycle collectors today, with pristine first-year examples regularly fetching $30,000 to $50,000 or more at auctions. In an era of sanitized, electronic safety nets stifling motorcycle performance, motorcycles like the H2 showed you what unfiltered, scary performance felt like.