Kawasaki H2 Mach IV

The H2 had “only one purpose in life,” according to Kawasaki’s 1972 sales brochure — “To give you the most exciting and exhilarating performance.” It also mentioned how the H2 “demands the razor sharp reactions of an experienced rider,” and is “a machine you must take seriously.”

Seriously, indeed. Consider: Seventy-four explosive horsepower stuffed into a powerband only 2,800rpm wide; a frame better suited to a moped; fuel consumption that would drop below 20 miles per gallon; spark plugs that fouled in less than 10 minutes of city riding; and all this accompanied by clouds of blue smoke and the raucous ring-a-ding racket of a big air-cooled multi-cylinder two-stroke.

The motorcycling equivalent of the Sex Pistols, the Kawasaki H2 Mach IV 750 stuck its middle finger firmly in the face of respectability when it burst onto the road in 1972. Essentially a scaled-up version of the Kawasaki H1 Mach III triple, with equally evil handling and similarly violent performance, the Mach IV was, in the hands of an inexperienced rider, an accident waiting to happen.

“Admiring it from a distance was safer than climbing aboard,” wrote Mac McDiarmid in his book Classic Superbikes. “The big Kawasaki’s uncompromising nature would quite possibly be outlawed today.”

Tracing the Triples

1972 was a banner year for quick bikes, and 750cc was the class to be in — not least because of the popularity of Formula 750 racing. Norton released the Combat version of its award-winning Commando with over 120mph on tap, MV Agusta had announced its 750S a year before, the Suzuki GT750 was soon to be in the showrooms, the Moto Guzzi V7 Sport was launched and Paul Smart won the Imola 200 on the brand new Ducati 750SS.

Kawasaki’s contribution to the need for speed employed technology it already understood. Strokers were its bread and butter, and the 1972 H2 Mach IV owes much to the three-cylinder H1. Producing 60hp at 7,500rpm (with precious little power below those revs) and weighing only 410lb, the H1 became the benchmark for outrageous street performance. With the proliferation of 750cc Superbikes, Kawasaki was spurred to up the ante. Though it had originally planned the H2 as a 650, the 750cc imperative made the extra cubes an easy choice, and may explain why the H2 engine has somewhat more “oversquare” dimensions than the 500.

Instead of 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. Its 70mm diameter pistons topped a 62mm stroke, with a 120-degree crankshaft running on six main bearings. Three Mikuni 32mm carburetors provided the fuel-oil-air mixture (a pump fed oil to each carburetor float bowl as well as to the crankshaft), and a Mitsubishi capacitive discharge ignition system provided the sparks.

Launched in late 1971, the 750cc H2 weighed just 40lb more than the 500cc H1, yet produced a class-leading 74 crankshaft horsepower at 6,800rpm. By comparison, its closest power rival in the 750 field, the Triumph Trident, could claim only around 58hp. The H2 had another significant advantage over its rivals: At under $1,400 — including the 10 percent import duty then in force — it was $300 cheaper than either the Honda CB750 or the Norton Commando Roadster, and $430 cheaper than the Trident.

In spite of the wide-ranging skills that must have been available within the Kawasaki Heavy Industries group, motorcycle frame design did not seem high on their list of capabilities. The H2’s lightweight tubular cradle was incapable of containing the vicious thrust of the peaky stroker. The frame flexed under cornering, while any surface irregularity at speed would destabilize the front wheel, causing a disconcerting weave, and making precise positioning on the road something of a gamble. The H2’s weight was also biased toward the rear, which, combined with a short swingarm, caused the front wheel to lift under acceleration if the rider was unprepared.

However, in the hands of a competent pilot, the H2 could be made to perform extremely well. In a 1973 Cycle seven-bike shootout, the H2 was awarded top rating, especially in terms of value for money, beating every other contender on performance except its own erstwhile successor, the 903cc four-stroke Kawasaki Z1.

In 1973, Kawasaki made a small number of mainly cosmetic changes, including a chrome front fender instead of the 1972 painted item. For 1974, the H2 saw numerous engineering changes, including porting revisions and a longer swingarm to tame the peaky power delivery, improve fuel consumption and stabilize the handling. But time was running out for big strokers: they simply couldn’t meet new emission regulations without significant added expense. The new realities of the mid-1970s — oil crises, safety, environmental and noise regulations — put the H2 in the same position as Richard Nixon. They both had to go.

But Kawasaki was ready with a winner in the wings: In 1973, the company trumped its own ace with the 900cc DOHC four-stroke Zl. And the rest, as far as high-performance Kawasakis are concerned, is a recent, but very rich, history. MC

Press Reports

“As expected, the Mach IV is an absolute jet, leaves all sorts of rubber on the pavement, pulls strongly in every gear, and shows absolutely no lag as you click your way from first to fifth.”
— Cycle World, November 1971

“Like its predecessor, the Mach III, the new 750 Mach IV is a rocket. The only drawback is that getting to the moon first, or to the next tavern as the case may be, costs money. If your daddy has a gas station and your uncle owns a tire store you’ll be better off than most Mach IV owners. If not, the local gas pump jockey will be on a first name basis with you and the tire man will call you up on your birthday.”
— Cycle, December 1971

“The Mach IV rates as the ultimate stud bike right now available in terms of raw power and sheer speed, although it does lack the refinement of some strictly touring machines. If being the fastest on your block appeals to you, so will the Mach IV!”
— Cycle World, March 1972

“The Kawasaki H2B is perhaps the best remaining example of the superbike concept — where performance is paramount and very little interferes with it. Its superbike character is manifested in its engine, which has more power and performance than any other 750 street machine.”
— Cycle Guide, September 1974

“Without a doubt, Kawasaki’s awesome 750 Triple is a bike that has outlived its usefulness. It was conceived at a time when the buying public was preoccupied with acceleration. Gut-grabbing acceleration. And little else. And the bike delivered to the tune of mid-12-second quarter-miles and wheelies that would stop your heart.”
— Cycle World, March 1975

“Time has dictated that a change is due. Perhaps overdue. And in a way that’s sad because brute power machines like the H2 turned a lot of people on at a time when all of us could afford to be carefree.”
— Cycle World, March 1975

Read more about the motorcycles mentioned in this article: 

• 1970 Kawasaki H1 Mach III
• Suzuki GT750
• Moto Guzzi V7 Sport
• 1968 Triumph Trident T150
• Honda CB750: A Classic for the Masses
• 1973 Kawasaki Z1: King of the Road