1972 Kawasaki H2 750 Mach IV

Below three separate writings tell the story of the H2. All three have been modified, but tell similar interesting stories about this motorcycle.


The Kawasaki H2 Mach IV was a 750 cc 3-cylinder two-stroke production motorcycle manufactured by Kawasaki and sold from September 1971 through 1975.


It became known as "The King of the Streets".  A standard, factory produced H2 was able to travel a quarter mile from a standing start in 12.0 seconds. It handled better than the Mach III that preceded it. By the standards of its time, its handling was sufficient to make it the production bike to beat on the race track.


Nonetheless, its tendency to pull wheelies and a less than solid feel through high speed corners led to adjustments to the design as it evolved. More than any other model, it created Kawasaki's reputation for building what motorcycle journalist Alastair Walker called, "scarily fast, good-looking, no holds barred motorcycles", and led to a further decline in the market place of the British motorcycle industry.


History

In September 1971, the H2 was a direct result of the success of the 500 cc Kawasaki H1 Mach III introduced in 1969. The H2 engine was a 3-cylinder two-stroke with an engine displacement of 748 cc (45.6 cubic inches) which produced 74 horsepower at 6,800 rpm, a power-to-weight ratio of 1 hp to every 6 lb of weight. This was an entirely new engine and not a bored-out 500. Unlike the H1 500, the 750 had much more low engine speed torque, with a strong burst of power starting at 3,500 rpm to the 7,500 rpm redline.


The 1972 H2 came with a single front disc brake (a second disc brake was an optional Kawasaki part), an all-new capacitor discharge ignition system unique to the H2, a chain oiler, a steering friction damper and a hydraulic one.


In 1973, there were minor mechanical changes made to the carburetor jets, oil injection pump and cylinder port timing in an effort by the factory to get more MPG from the H2A. The most powerful H2s were the 1971 and the very early 1972 models.


In 1974, the H2B engine was modified for more civilized performance at the expense of raw power. The race tail was slimmed down from the previous year. An oil-based steering damper and check valve were added. The power was reduced to 71 horsepower at 6,800 rpm. The oil injection system was substantially changed with two separate sets of injection lines, unlike the earlier models with one set of lines. Oil was injected into the carburetors on a separate line with a branch to each carburetor. The oil injection to the bottom end bearings (both main and rod big ends) was retained as a set of three separate lines as before. A longer swingarm improved stability. The final model had a weight of 459 pounds (208 Kg).


The H2B and H2C had the steering damper repositioned to the left.


Racing tail

In 1972, Kawasaki designers took a progressive leap forward in overall design appearance with the creation of the first race tail on the H2 as well as on the 350 cc S2 Mach II. The race tail covered most of the taillight assembly behind the seat and allowed for a less conspicuous rear fender. This design innovation would be copied and seen on the 1977 Yamaha RD250 and 400 and nine 1978 Suzuki models, beginning with the GS1000 down to their 250 cc bikes.

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Yes, indeed, Kawasaki’s 1972 Mach IV—a.k.a. the H2—was shockingly quick for its day, faster than most street riders could wrap their heads around. It ran low 12s at the strip, quicker than any streetbike in history. It wheelied too easily in first gear, surged and shook like a wet dog at certain revs, got lousy fuel mileage (high teens when ridden hard), was loud, and smoked like a chimney. Yes, the very recipe for success.


The story of the 1972 Kawasaki Mach IV H2 750 begins, of course, with the Mach III H1 of 1969, a 500 cc two-stroke triple conceived, designed, and built during the latter 1960s—a time when Kawasaki, new to the US market, was looking to elbow its way in. The peaky-yet-fast H1 did its job well, catapulting Kawasaki—which had only 250 cc and 350 cc two-stroke twins and a 650 cc four-stroke twin—to the top of the performance ladder despite the launch of Honda’s refined (but heavier and slower) CB750 Four that same year.


And the H1’s cornering performance was damned…damned bad. “It wobbled at speed,” remembers longtime Kawasaki test rider and race-team mechanic Steve Johnson, “and dragged its undercarriage in fast corners.” Still, Team Green didn’t worry much; it was out to build a performance reputation, and, at the time, brutish, arm-straightening power was the quickest way to the prize. “Finally,” Johnson says, “Kawasaki had something to sell to folks wanting a big, fast, and nasty streetbike, a bike that could outrun anything out there. Kawasaki didn’t even hint at handling or cornering; it was all about acceleration and top speed. When the (H1s) came out they were instantly all over the dragstrips.”


Focusing on speed—not refinement or handling, which the CB750 had in spades—was a bit of a risk, but Kawasaki happily took the chance. “Kawasaki was a much bigger company and could afford to be risky,” says longtime US Suzuki manager Jim Kirkland. “A friend at Kawasaki back then told me they built crazy bikes like the H1 and H2 for the publicity.”


Despite Honda’s successful four-stroke four-cylinder CB750, Kawasaki knew two-stroke triples still made sense. They were narrower than fours, made more power per cc, and were lighter than similarly displaced four-strokes. Plus, Kawasaki had been developing two-strokes for some time, gaining the experience to produce eye-watering power. Finally, while the EPA had yet to clamp down on exhaust emissions, there were signs that both the tailpipe emissions and high fuel consumption of two-strokes would no longer overcome their performance advantages. But not yet.


As early as mid-1969, Kawasaki engineers conceived a bigger H1, and within months 650cc versions began circulating. Test mules were refined, with modified frames, disc brakes, and as much suspension tuning as engineers could muster. And by late 1970 a couple prototypes made their way to California for some serious testing.


As Kawasaki’s primary test rider at the time, Steve Johnson remembers that H2 prototype pretty well. “It was a 650,” Johnson says, “and it arrived with a small team of test riders and engineers. We developed a plan and headed north on Route 395 with a chase van full of parts and a spare bike. Right away, the Japanese test rider wanted to show me how fast the bike was and within minutes got pulled over for doing 120 mph-plus. The cop was pissed and wanted to haul him away but was frustrated by his near-total lack of English. I somehow talked the officer out of arresting him, and he let us go.”


A day later the group ended up on a curvy part of Interstate 80 in western Nevada. “The guy in charge,” Johnson says, “told me, ‘Steve-san, we will use this section for high-speed cornering test, and we will film you. Please ride as fast as possible!’ I’m saying, ‘You’re nuts!’ but began doing laps anyway, cutting through the median to turn around, as the nearest on-ramp was miles behind us.


“The thing had a super-tall first gear and was peaky,” Johnson says, “not as bad as the 500, but close. It wobbled at speed every time through too; I just sorta hung on and prayed. After several runs I came in. ‘Very good,’ they told me. ‘Now we do shock testing!’ This went on all day, with the camera going the whole time.”


Once back at Kawasaki’s R&D headquarters in Santa Ana, all agreed that high-speed stability was unacceptable; power delivery was too abrupt; first gear was too tall; and the brakes could be better. Six months later, another bike arrived—only this time it was a final-spec pre-production machine, not a hand-built prototype. It was also a 750. “It was much better,” Johnson says. “And more refined. Power was up and the delivery was smoother. Its gearing and brakes were better, too, and the wobbles were mostly gone. The team did a good job.”


Magazines got early test units in the fall of 1971, and the results were explosive and immediate. The bike was instantly faster in terms of quarter-mile elapsed time and top speed than anything available and was reasonably functional—the vibration, noise, surging, and mileage issues notwithstanding.


Longtime Motorcyclist editor Art Friedman tested a first-year H2 while working for Cycle News and found it funky yet functional. “It was actually a pretty good sporting streetbike despite its quirks,” Friedman remembers. “It was no tourer, but it handled well and had good brakes, even when ridden hard in the twisties… And, boy, was it fast! That stuff made you forget about the vibes, smoking, and surging. It was also a great production racer. I raced several H2s during the 1970s and won a lot of races on them, even finishing sixth in an early AMA Superbike event at Laguna Seca. It was bone stock except for Dunlop K81s, Koni shocks, and a swingarm bushing kit.”


Motorcyclist agreed with its future editor in its January 1972 road test, chronicling the bike’s many bothersome quirks but reveling in its breathtaking speed, great brakes, and secure handling, even when ridden hard. “Handling is far better than expected and a vast improvement over the sometimes snaky Mach III,” the editors wrote. “Thankfully, the 750’s geometry and suspension are up to the job. With this engine a rider can be over his head with alarming frequency, yet the chassis will save him by rifling through turns without any scraping or undue waver.” Although ambivalent about the H2 in many ways, the magazine capped its test report with this: “A 12-second 750 for $1,395? So what if it shakes?” If the press opinion after the launch of the H2 tells you anything, it’s that Kawasaki took the criticisms of the prototype to heart and developed a much improved machine for production.


The H2 lasted just four years, from 1972 to ’75. It was a golden era for motorcycling, with unreal sales and amazing advancements in performance and reliability. The two-wheeled environment morphed radically during that time too. Kawasaki had launched its mighty, four-stroke 903 cc Z1 in ’73. Smog laws, for better or worse, laid the groundwork for the end of the two-stroke streetbike era. The Arab oil embargo of late ’73 tripled the cost of oil. And more importantly, the big streetbikes of the day were becoming civil and fast, a combination the H2 certainly did not possess—even as Kawasaki embarked on a campaign to soften power and improve stability with a longer swingarm.


The legacy and impact of the H2 and its four-year run lingers, like blue tire and exhaust smoke hovering above the Orange County Raceway’s Christmas-tree lights. During those crazy, On Any Sunday-flavored ’70s, the H2 was fast, daring, emotional, and, yeah, full of quirks. It remains that way today, wholly fascinating in just about every way.

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The 1972 Kawasaki H2 sales brochure read, “We've just pulled a fast one on the competition. Named the Kawasaki 750 cc Mach IV. Of all the world's production models, it's the fastest thing on two wheels. Faster than any Suzuki. Faster than any Triumph. Faster than any BSA, and Honda, any anything.”


The H2 was designed for one thing and one thing only: speed. Noise, pollution, fuel consumption, even handling were all afterthoughts.


Unlike the disc- and reed-valve two-stroke designs then coming on to the market, Kawasaki stuck to a piston-port design for simplicity and compactness. Three Mikuni 32 mm carburetors provided the mixture, and Kawasaki's new Capacitor Discharge Ignition lit the fire.


It was a basic set up, but it worked. The Mach IV put out and eye watering 74 bhp (its closest rival, the Triumph Trident, could muster only 58 hp) but weighed just 8 kilos more than the H1. The result was arm-wrenching acceleration and a blistering 126 mph top speed. The industry, the press and the riders of the day hadn't experienced anything quite like it.


There was just one problem the H2’s lightweight tubular cradle frame was simply incapable of containing the vicious performance of the motor. It flexed under cornering, weaved horribly on uneven roads, making finding the right line and sticking to it almost impossible. Kawasaki fitted two steering dampers (one friction and one hydraulic) but they didn't make much difference.


On top of that, most of the Mach IV’s weight was over the rear wheel, which – combined with a short swingarm – caused the front wheel to go skywards, if the rider wasn't easy on the throttle. And that wasn't easy to do: the whole 74 hp was delivered in an incredibly narrow power band.


In the hands of an experienced rider, the Mach IV was the fastest production bike in the world, but with someone less skilled on board, it was an accident waiting to happen. It earned its nickname 'the widow maker' all too often.


By 1974 Kawasaki had made a few chassis alterations and tweaked the motor to tame the terrifying power delivery, but by the standards of the day the H2 was a still a hooligan.


It wouldn't however be just it's reckless reputation that sealed the H2s fate. By the mid-70s the realities of an oil crisis', and increasingly strict safety, environmental and noise regulations meant the writing was on the wall for all the big strokers. The last H2 howled off into the distance in a haze of blue smoke in 1975.

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1972 Kawasaki H2 750 Mach IV Specifications

Engine:  Air-cooled, two-stroke, transverse three-cylinder
Engine capacity:  748 cc (45.65 cubic inches)
Bore x Stroke:  71 x 63 mm
Compression Ratio:  7.3:1
Induction:  3 x 30 mm Mikuni VM30SC carbs
Lubrication:  Oil injection
Starting and ignition:  Kick start; battery and coil CDI
Max Power:  74 hp  @ 6800 rpm
Max Torque:  7.9 kg-m @ 6500 rpm
Transmission:  5-speed, chain drive
Gear Ratios:  1st 12.75:1 2nd 8.64:1 3rd 6.53:1 4th 5.42:1 5th 4.76:1
Clutch:  Wet multi-plate
Frame:  Double tubular steel cradle
Front: Suspension:  Telescopic hydraulic forks (non-adjustable)
Rear Suspension:  Dual shocks (preload adjustable), Swing arm
Brakes:  Single disc (front) Drum brake (rear)
Braking:  30-0 in 33 ft.; 60-0 in 111.7 ft.
Tires:  3.25 X 19 (front), 4..00-18 (rear)
Dry-Weight: 423.2 pounds
Fuel Capacity: 4.49 gallons
Acceleration:  0-30 in 2.9 sec.; 0-60 in 5.0 sec.; Standing ¼ mile: 12.3 sec. @ 105 mph
Top speed:  126 mph