The Kawasaki H2 750 Mach IV (1972): the two-stroke that terrorised the 1970s

ModelKawasakiTwo-stroke

First thing to untangle, the names: the H1 is the Mach III with 498.8 cm³, the H2 the Mach IV with 748 cm³, launched in 1972. Its air-cooled two-stroke triple puts out 74 hp at 6,800 rpm, runs the quarter mile in a little over twelve seconds and tops out around 190 km/h, for $1,386. Flexy frame, barely adequate brakes, fuel consumption of 8 to 13 litres: the nickname Widowmaker, born on the H1, sticks to it all the same. Discontinued in 1975 after roughly 50,000 units.

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H1, H2, Mach III, Mach IV: putting the names back in order

Before we talk horsepower, let's clean up the vocabulary: that's where 90% of bar-room arguments go off the rails. At Kawasaki, the “Mach” names don't designate generations but displacement tiers within a single family of two-stroke triples. The S1 is the Mach I (250 cm³), the S2 the Mach II (350 cm³), the H1 the Mach III (500 cm³) and the H2 the Mach IV (750 cm³).

In concrete terms: the H1 500 Mach III arrived in 1969, the H2 750 Mach IV in 1972. Two different bikes, three years and 250 cm³ apart. Saying “the Mach III 750” mixes up two machines whose characters have nothing in common. If the H2 badge speaks to you mainly through its supercharged reincarnation, our feature on the Kawasaki H2R shows how fully the brand owns the legacy of that name, and the Kawasaki saga puts those years back in their industrial context.

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748 cm³, three cylinders, 74 hp: the anatomy of a missile

At the heart of the H2 sits an air-cooled 748 cm³ two-stroke inline triple, bore and stroke 71 × 63 mm, compression 7.3:1, with piston-port induction — no exhaust valve, no electronics, just brutal thermodynamics. Fuelling is handled by three 32 mm Mikuni carburettors and ignition by a Mitsubishi CDI, genuinely modern for 1972. Lubrication runs through a separate oil injection system, the pump feeding the carburettors and the crankshaft bearings.

Claimed output is 74 hp at 6,800 rpm, with a torque figure of 77.4 Nm at 6,500 rpm. The number looks modest today; it has to be judged against its era. Road tests of the day summed the H2 up as one horsepower per 5.7 pounds, a ratio very few road bikes could claim — with the spec sheets quoting, depending on the source, 192 to 205 kg dry. More to the point, unlike the H1 500, known for being hollow down low, the 750 had real torque from 3,500 rpm, with a shove that then came in like a switch all the way to the red line at 7,500 rpm. This was not a bike for “playing with the revs”: it was a bike to hang on to.

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In a straight line, nobody kept up

The period numbers still raise a crooked smile. The H2 knocked off 0 to 60 mph (≈ 97 km/h) in 4.1 seconds and the quarter mile in a little over 12 seconds, with a top speed of around 190 km/h (120 mph), some tests even claiming a little more. In 1972, those figures put the Kawasaki above everything else sold in a dealership, including the Honda CB750 Four which had, after all, invented the superbike concept three years earlier.

Cycle, in December 1971, summed it up in a line that stuck: the new 750 Mach IV was “a rocket” — the magazine adding that going to the Moon, or just to the next bar, still came at a price. That price, precisely, was almost indecent: $1,386 for the fastest bike in the American catalogue. It is that performance-to-price ratio that built the legend, and that still puts the H2 into every conversation about the fastest road bikes. Then there is the detail that built the imagery: the H2 lifted its front wheel with disarming ease, throttle pinned in second. Not a stunt: a side effect.

🏍️ Want a piece of that mythology at home? Our Kawasaki: Motorcycle Accessories & Decor section covers a lot of ground, from small everyday objects to workshop decor.

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The chassis and the brakes, though, never kept up

Here is the heart of the problem. The H2's engine was ahead of its time; everything else came from the previous decade. The frame is a tubular steel double cradle, light, sized for far less power, and it flexed under load. Conventional telescopic fork, twin rear shocks, 1,410 mm wheelbase, narrow tyres: coherent for a mild 500, not for 74 hp delivered in one block. Kawasaki had in fact fitted two steering dampers, one friction, one hydraulic — the manufacturer's own admission.

The result was handling that fell apart exactly where it needed to be good: headshake and weaving in fast bends, with a lot of weight carried on the rear. Kawasaki fixed things model year by model year, notably with a lengthened swingarm in 1974 that clearly calmed the machine down. On the braking side, from 1972 the H2 got a single front disc (second disc optional) and a rear drum — better than the early H1's drums, but barely adequate for stopping 200 kg travelling at 180 km/h.

This is the typical Japanese imbalance of the early 1970s, which the Laverda Jota would later tackle from the other end: chassis first, horsepower afterwards. On a classic, that imbalance always starts with the tyres — all the more reason to know how to check the wear on a motorcycle tyre.

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“Widowmaker”: who the nickname really belongs to

This is the awkward question, and the answer is more interesting than the myth. The nickname “Widowmaker” was born on the H1 500 Mach III, not on the 750. The clearest account comes from Tony Nicosia, a test rider for Kawasaki at the time, who explains that the term came from the board track era and that they applied it to the H1 because it could flip over backwards and throw you on the ground, or go into a tank-slapper at high speed.

The H1 had what it took to earn the label: around 60 hp at 7,500 rpm from 498.8 cm³ and barely 174 kg dry, a quarter mile timed at 12.96 s at 100.7 mph (162 km/h) for $999, and above all drum brakes until 1971 — the 296 mm front disc only arrived in 1972. Add a flexy frame and skinny tyres, and you get the bike the Americans also nicknamed “the triple with the ripple”.

So why does the nickname stick to the H2? Because the 750 inherited the reputation and amplified it : more torque, more speed, the same foundations. In everyday use, “Widowmaker” now covers both. Historically the H1 owns it, culturally the H2 has confiscated it — as long as nobody claims the name was born in 1972.

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The “green bike” legend: what the brochures actually said

You read everywhere that the H2 was “the green bike”, a shortcut between Kawasaki and its apple green. That is false for the vast majority of H2s. The catalogue colours were deep candy shades, very much of the 1970s, and green only shows up late and occasionally:

In 1972 (H2), the bike came in Pearl Candytone Blue and Pearl Candytone Gold — the American market only receiving the blue, the gold going for export. In 1973 (H2A) : candy gold or candy purple. In 1974 (H2B) : candy brown or candy green. In 1975 (H2C) : candy purple or candy super red. In other words, only one year offers a green, and it is a dark candy green, not the fluorescent racing green.

Because the famous Kawasaki lime green is a 1969 American marketing invention, devised for the race machines entered in the Daytona 200 : the subsidiary wanted bikes you could identify in a race that was by then shown on colour television. The livery is the work of designer Chris Kurishima and painter Rollin “Molly” Sanders — a deliberate provocation, green dragging along a reputation as an unlucky colour on the racetrack, Harley-Davidson leading the way. That green therefore belongs to American racing and to motocross, not to the factory paint of the road-going Mach IV.

🖼️ To dress a wall in the real colours of the era, take a look through our Motorcycle Posters & Prints.

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Thirst, smoke and the end of the two-stroke's reign on the road

The H2 had one flaw that neither talent nor restoration can fix: it drank. Period tests recorded between 18 and 28 mpg, roughly 8 to 13 litres per 100 km — nearer the top of that range as soon as you opened the throttle. With a 17-litre tank, usable range then dropped to around 130 km. On top of that came the original sin of the big two-stroke: burnt oil, unburnt fuel, blue smoke and noise.

The 1973 oil crisis did the first culling, American regulation did the rest: the federal environmental agency published in early 1977 emissions standards applying to motorcycles from the 1978 model year, coupled with mounting constraints on noise. For a 750 cm³ two-stroke triple, the equation became unsolvable. The H2 was discontinued after 1975, after roughly 50,000 units ; the surviving triples were renamed KH and dropped in displacement, the 1976 KH500 making no more than 52 hp. By 1980, all that was left were the KH250 and KH400, and only in Europe.

The road-going two-stroke did not disappear for all that: it took refuge in small and mid-size displacements, where its power-to-weight ratio remained unbeatable. That is the story of the Yamaha RD350 LC, and then the last stand of the RD500LC.

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The H2's real job: holding the door until the Z1

The H2 is not an industrial accident: it is a piece on the chessboard. As early as 1967, Kawasaki was secretly working on a 750 cm³ four-stroke four-cylinder, a project led by engineer Gyoichi “Ben” Inamura and codenamed internally “New York Steak” — the best cut on the menu. The unveiling of the Honda CB750 at the Tokyo Motor Show on 25 October 1968brought the plan crashing down: Honda had just released exactly the bike Kawasaki was preparing.

The response was to revise the brief upwards, moving to 900 cm³ (903 cm³ to be exact) with orders to beat the Honda. That detour left a gap to fill, and that is precisely the H2's mission in 1972 : to carry the performance flag and keep up the “Kawasaki = the fastest” image while waiting for the four-stroke. The Z1 900 was unveiled in September 1972 at the Cologne show : the two briefly coexisted, with two opposing philosophies.

The rest is well known. The Z1 offered the same straight-line violence with civilised fuel consumption, a healthier chassis and four-stroke reliability — it made the Mach IV obsolete in two seasons, as our article on the Kawasaki 900 Z1tells it. What is left of the H2 is not a race record: it is the memory of a bike that did not forgive, and that cast Kawasaki in the role of the manufacturer that goes too far — a reputation never dropped since, right up to its Grand Prix adventures.

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Summary table

📖 Read also: The Yamaha TZ750: the two-stroke nobody really dared to tame.

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FAQ — Frequently asked questions

• Is the Kawasaki H2 750 the real “Widowmaker”?
  Historically, no: the nickname was born on the H1 500 Mach III of 1969. Kawasaki test rider Tony Nicosia explained that the term came from the board track era and that it was applied to the H1 because it could flip over backwards and throw its rider to the ground, or go into a tank-slapper at high speed. The H2 750 then inherited the nickname and popularised it, so much so that today it commonly refers to both machines.
• What is the difference between the Mach III and the Mach IV?
  They are two different displacements within the same family of two-stroke triples. The Mach III is the 498.8 cm³ H1, launched in 1969; the Mach IV is the 748 cm³ H2, launched in 1972. The range also included the 250 cm³ S1 Mach I and the 350 cm³ S2 Mach II.
• How much power does the Kawasaki H2 750 Mach IV make?
  74 hp at 6,800 rpm on the 1972 model year, with 77.4 Nm of torque at 6,500 rpm. Power was brought down to 71 hp on the final model years. Period tests summed the machine up as one horsepower per 5.7 pounds — for a claimed dry weight of between 192 and 205 kg depending on the source — an exceptional ratio in 1972.
• Was the Kawasaki H2 green from the factory?
  Almost never. The catalogue colours were candy shades: pearl blue and gold in 1972, gold or purple in 1973, brown or green in 1974, purple or red in 1975. Only the 1974 model year offers a green, and it is a dark candy green. The lime green associated with Kawasaki is a 1969 American marketing creation reserved for race machines, notably at the Daytona 200.
• Why was the Kawasaki H2 discontinued in 1975?
  The combination of the 1973 oil crisis, fuel consumption of 8 to 13 litres per 100 km, the tightening of American noise rules and of emissions standards applying to motorcycles from the 1978 model year, and above all the arrival of the four-stroke Z1 900, more frugal and better behaved. The surviving triples were renamed KH and dropped in displacement.

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