Heavy Metal: 1975 Kawasaki H2 Mach IV 750

The Kawasaki H2 Mach IV 750 was to other motorcycles what heavy metal was to rock and roll — outrageous.

Kawasaki front view

1975 Kawasaki H2 Mach IV 750

Photo by Nick Cedar

Content Tools

1975 Kawasaki H2 Mach IV 750
Top speed:
110mph
Engine:
748cc air-cooled 2-stroke triple, 71mm x 63mm bore and stroke, 7:1 compression ratio, 71hp @ 6,800rpm
Weight (dry):
448lb (204kg)
Fuel capacity/MPG:
4.5gal (17ltr)/28-30mpg
Price then/now:
$1,825/$2,000-$12,000

Remember heavy metal? Back in the day, heavy metal was loud guitars playing songs in minor keys with occult themes and horror-movie lyrics, raging about social instability, political corruption and apocalyptic prophecies. The music was provocative, and like heavy metal, the Kawasaki H2 Mach IV 750 triple was outrageous, loud, uncivilized and exciting. It was horsepower personified.

From its late 1971 U.S. debut on, of all places, the Queen Mary ocean liner, the Kawasaki 750 2-stroke triple showed it had what power-hungry bad boys wanted: a 74 horsepower engine powering a bike with a curb weight of 450 pounds. The Mach IV was to other contemporary motorcycles what heavy metal was to rock and roll — in a word, outrageous.

Building up

The company behind the 750 triple, Kawasaki Heavy Industries, was as much unlike its progeny as one could get. A huge, well-established, diversified company, it built (and still builds) ships, railroad rolling stock and electrical plants. The motorcycle division came after World War II, following Kawasaki’s forced exit from aircraft manufacturing. In the 1960s, the rapidly-growing Kawasaki motorcycle division saw Honda as its archrival, and gaining points and publicity at the expense of Honda became a prime objective.

Kawasaki’s first major score against Honda came in late 1968, the same year Black Sabbath, considered by many as the first metal group, was formed. The score was the introduction of the 500cc H1 Mach III, a blazingly fast 2-stroke triple with electronic ignition. It was a light bike with a strong engine and weak brakes — not the best combination for the speed-crazed boys who tended to buy it. The H1 was popular, sold well and put Kawasaki on the map. It spawned a smaller 350 version, which was widely held at the time to have better handling. Later versions of the H1 had better brakes and a stiffer frame, but it was still fast and exciting.

In the meantime, Honda had made history with its CB750 Four, a much more civilized motorcycle. Kawasaki had its own 750cc 4-cylinder in development when the CB750 came out in 1969, but decided to postpone the introduction of its new 4-stroke until it could come up with something that would definitively trump Honda. In the meantime, Kawasaki built on its loud ’n proud image by designing a 750cc version of the controversial 500.

The Mach IV cometh

Contemporary magazine writers could not wait to get their hands on this beast. “The new 750 Mach IV is a rocket,” burbled Cycle. Period moto journalists noted that the new Kawasaki had an appetite for both fuel and tires, but it didn’t matter. The 2-stroke triple looked good, it was fast and made great noise, and it ran 12-second quarter miles straight out of the box. What more did a young man need? “The Mach IV is worth every extra nickel for the sheer pleasure of leaping from a dead stop to 100mph in less time than it takes the average rider to buckle his helmet,” Cycle continued.

The first version of the Mach IV was powered by a 748cc piston-port triple developing a claimed 74 horsepower at 6,800rpm. Today that isn’t anything to write home about, but in 1971 that horsepower figure was impressive. Interestingly, instead of just enlarging the 500, Kawasaki’s engineers designed the new model from the ground up. Easier-to-balance triangular flywheels were used to offset the weight of the pistons and rods. The main bearings were considerably larger than the ones on the 500, but piston port timing was milder, for better lower-end pull and a wider powerband. The porting included one intake, two transfer ports and one exhaust port per cylinder. Lubrication was pressure fed to each cylinder’s crank from an oil tank, and like its H1 predecessor it used a CDI electronic ignition.

The chassis showed lessons learned from Kawasaki’s experience with the 500. An 11-inch disc on the front and a 7-3/4-inch drum on the rear provided much better stopping power, although testers pointed out that the brakes would fade after repeated hard stops. Extra triangulation and frame stiffness were gained by adding an extra diagonal tube between the swing arm pivot and the top frame tube. One of the major problems with the 500 was the bendy frame: The 750 frame was much stiffer.

Besides the brake fading, testers pointed out the engine’s tendency to surge between 35 and 45mph, and noticeable chain stretch. But it really didn’t matter, because everyone wanted to experience the 750’s power and acceleration. The Mach IV was a popular machine.

Two-strokes rule

While some folks were celebrating noise, speed and rock ’n’ roll, other folks were concerned about the environment, and their concerns reached the ears of government. Ultimately, increasing emissions restrictions doomed road-going 2-strokes. It has been argued that it is possible to make clean-running 2-strokes. However, it was easier (and therefore more commercially practical) to build clean-running 4-strokes. Kawasaki finally developed a new 4-stroke motorcycle to its satisfaction, announcing the 903cc Z1 in 1972. Not only was the Z1 powerful, it was also quiet, comfortable and handled reasonably well.

Cycle conducted a Superbike Shootout in late 1972, and invited Kawasaki to bring both the 750 Mach IV and its 900 Z1 4-stroke to the festivities. The test, specifically limited to braking, acceleration and cornering, pitted the two Kawasakis against the Honda CB750 Four, a Norton Commando 750 twin, a Triumph Trident 750 triple, a Ducati 750GT twin and a Harley-Davidson Sportster 1000. Surprisingly, the Mach IV won the braking contest, and tied for best lap time on the road race course. It ran the quarter-mile in 12.28 seconds, with the Z1 coming in second at 12.386 seconds. On that basis, Cycle declared the Mach IV the winner of their Superbike Shootout, while pointing out that other bikes in the test had better road manners and were easier to ride.

Despite the success of the Z1 4-stroke, the Mach IV stayed in production. Its owners turned up at Guns N’ Roses and Van Halen concerts, wowed the crowd at the diner with burnouts, and tried their hands at a little illegal road racing. A significantly updated version, the H2B, appeared in May of 1974. Cycle Guide got their hands on one, intending to find out if the bike was still a delinquent, and published its test results in the September 1974 issue. “When the bike was finally released, the big question was whether or not the performance had been left out when the other niceties were installed.”

The changes made to the 1974 model included aluminum throttle slides in the Mikuni carburetors, a feed from the oil injection pump to the carburetor float bowls, plus a 2-inch longer swingarm, producing an almost 57-inch wheelbase. In the process, the center of gravity was moved forward, adding to straight-line stability. Horsepower, however, dropped from 74 to 71.

The engine dimensions were unchanged. Neutral was, confusingly for some riders, still at the bottom of the shifter throw, and it was still a kickstart-only machine. Also unchanged was the kick when the engine reached its powerband, at just more than 4,000rpm. Cycle Guide’s best quarter-mile time was 12.96 seconds; slower than the earlier model, but that was blamed on a slipping clutch. Several months later, Cycle World tested the new version, but even with a good clutch, their testers couldn’t wring sub-13 second times out of the animal. The beast had been tamed — somewhat.

Despite the improvements, the Mach IV still had bad habits, which helped retain its antisocial aura. The engine was noisy and prone to surging in first and second gear, and it still gulped gas, averaging 30.6mpg during Cycle Guide’s testing. The rear shocks, with three preload positions, had poor damping and the bike bounced hitting bumps, and testers complained of vibration through to the handle bars above 3,500rpm. Cycle Guide concluded, “The enthusiast who has watched the high-performance machines of a few years ago fade into blandness as they gained refinement will find the Kawasaki Mach IV a refreshing change. Its manners may have improved a bit, but the performance is still there.” 1975 was the last year for the Mach IV. Despite continued popularity, the difficulty of making it EPA compliant doomed it to extinction.

Andreas Strieve’s Mach IV

Meanwhile, motorcycle enthusiast-to-be Andreas Strieve was growing up. He went off to college, and promptly bought a Yamaha DT250 for transportation. A year or two later, Andreas achieved his childhood dream with the purchase of a 1975 Kawasaki Z1, which he still owns. “It started back when I was 8 or 9 years old,” Andreas says. “I saw a Z1 and an H2 racing up an alley. The sound was awesome. I thought, ‘Oh my God. I want one.’”

Although Kawasaki and Honda continued their rivalry with new, better-handling motorcycles, Mach IV owners refused to throw in the towel. They proclaimed their allegiance to their bad and nasty triples, and formed 2-stroke clubs, the better to keep the light of quarter-mile speed shining and spread the gospel of untamed horsepower. “There is a magic to these machines,” explains Andreas. “Members of 2-stroke clubs have a special camaraderie. Plus, club members are a helpful bunch of people. Information, advice and access to resources are freely given, but the hunt for parts is then your personal adventure.” Andreas had started collecting Japanese classics some 20 years ago. Recently, he realized that he wanted a 750. He started checking out friends’ bikes and looking at for sale listings. About six months ago, he found this purple 1975 H2C. “I rode it and it ran OK, so I took it home. I realized I didn’t know enough about this animal, so I took it to my mechanic, who has experience with older bikes. He found some things that needed work, and they were taken care of,” Andreas says.

Little by little, Andreas has cleaned up his purple monster. He drained and flushed the oil tank, refilling it with Amsoil synthetic oil. He replaced the plug wires, found a centerstand but not new handlebars (“handlebars do not exist,” Andreas says), and rebuilt all three carburetors. He found that some parts had been cut off by a prior owner to fit expansion chambers. The owner before Andreas removed the expansion chambers, but did not reweld the missing bits. Rewelding the missing tabs is a project for the near future. “Mine is still a work in progress,” he notes, adding that “the bike was repainted at some point, and it was not done very well. I plan to repaint in the next few months.”

Riding the Mach IV was another learning experience. First, there was the starting drill: “Petcock on, choke pulled and right footpeg folded up. This is important — the right peg interferes with the kickstarter. Give it a good hard kick or two, and then fold the peg down. Then you are off to the races,” Andreas says, although he notes that the shifting pattern, with neutral at the bottom, takes some getting used to. He also quickly found out that contemporary reviewers were not kidding about the Mach IV’s thirst. “I ran out of gas — a half mile from my house.”

Contemporary writers were all over the place about the Mach IV’s handling, with some enthused and some appalled. Andreas is middle of the road and philosophical. “It is a 40-year-old motorcycle,” he says, calling it “a decent bike for what it is. The frame has limitations, and I will not push it hard through the twisties. The brakes work fine, though the ride is a little rough and the springs have limitations. It’s a little bit like a tractor. I treasure the riding experience for what it is. It’s a wonderful little beast.

“It puts a smile on my face,” Andreas says. “The H2 is a thing of beauty, and if kept in good running shape it is something that will appreciate in time. I consider myself the temporary caretaker of this machine.” MC