Kawasaki H2 Mach IV
(Page 2 of 4)
July/August 2006
By Robert Smith
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 Kawasaki’s 1969 H1 three-cylinder Mach III. 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.
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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 750 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 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.