Four stroke, transverse four
cylinder, DOHC, 2 valve per cylinder.
903 cc / 55.1 cu-in
Bore x Stroke
66 x 66 mm
Wet sump, trachoid pump
Treated synthetic fiber
4 x 28mm Mikuni VM28SC
Battery and coil
Electric & kick
82 hp / 59.8 kW @ 8500 rpm
73.5 Nm / 54.3 lb/ft @ 7000 rpm
Straight cut gears
1st 12.79:1 2nd 8.84:1 3rd 6.74:1 4th 5.58:1 5th 4.92:1
Double tubular steel cradle
36mm Telescopic forks
Dual shock, 5-way preload adjustment
Single 296mm disc 2 piston caliper
Length 2209.8 mm / 87.0 in.
1498.6 mm / 59.0 in
818 mm / 32.2 in.
812.8 mm / 32.0 in.
170 mm / 6.75 in.
230 kg / 507 lbs
247.6 kg / 546 lbs
18 Litres / 4.7 gal
Braking Distance 30 mph - 0
Braking Distance 60 mph - 0
Acceleration 0-30 mph
Acceleration 0-60 mph
12.61 sec / 105.63 mph
The Z1 Chronicles
Kawasaki’s 900 Super Four Z1 did
more than blow past Honda’s CB750 in terms of performance,
refinement and all-around ability.
It was the world’s first superbike.
"A velvet blunderbuss, and every inch a
King."—Cycle, November 1972
For just a moment, imagine you're
Kawasaki's Sam Tanegashima in the fall of 1968. As a project
leader you've been slaving night and day for the better part of
two years on what was then internally known as N600. It is going
to be a groundbreaking road-burner that will become the most
important motorcycle in the world, with a contemporary
mass-production first of an air-cooled, DOHC, 750cc inline-four.
Testing is all but complete and has gone swimmingly—your finger
is metaphorically poised to push the button to begin production
early next year. You might even allow yourself to think life is
going to be very, very good.
And then you get the phone call from the 1968 Tokyo Motor Show.
It seems competitor Honda had the same idea—only a bit
sooner—and has knocked motorcycling on its ear with the
revolutionary CB750 Four. Suddenly there is indeed a new most
important motorcycle in the world—but it ain't yours. Shame and
frustration taste more acrid than bile. One remembers it with
So it was for Kawasaki's N600 project team as they returned to
Akashi to lick their wounds—and vowed to kick Honda's ass from
Tokyo to Tucumcari to Turin and back by building something
bigger, faster and even more sophisticated—a true King of
Motorcycling. It would take the better part of four years, an
eternity compared with current two-year product cycles for
today's 600cc and 1000cc sportbikes. But Kawasaki was determined
to get it right.
At the time Kawasaki was in the midst of changing its entire
approach to building motorcycles. As Tanegashima says in Micky
Hesse's book Z1 Kawasaki, "One motto [we had] for developing the
Z1 was to create one piece of motorcycle. Before the Z1,
Kawasaki had developed several very fast motorcycles like the
A7, H1 and H2. It was not sure if we were selling
engine/horsepower or motorcycle.
"From the very beginning of Z1 development," he says, "we made
sure to develop one piece of motorcycle, not independent engine
or chassis or designing."
Tanegashima added that the Japanese were
well known for their me-too approach—going along to get along,
so to speak. "Our people tend to like to do the same thing as
[their] neighbor. In product development, this tendency leads to
[copying] some competitors or leaders. However, [our] motto in
developing the Z1 was to make it completely different from
Honda's CB750. This [is] a very rare case in Japanese society."
Equally interesting is a passage from Kawasaki's museum Web site
(www.khi.co.jp/mcycle/museum/index_e): "[With the Z1] Kawasaki
changed their engine design policy so that the powerband was not
set near the engine's [rev] limit, thereby pursuing elegance and
smooth engine performance." At its heart, that change stemmed
from Kawasaki's decision to substitute four-stroke powerplants
for two-strokes in making top-of-the-line models. After all,
Kawasaki had in 1963 absorbed Meguro, one of Japan's oldest
motorcycle manufacturers and known for its four-strokes, so
Kawasaki had four-stroke engineering expertise. (To this day,
the firm still uses Meguro's logo on packaging and signage.)
Indeed, Kawasaki's talented engineer Ben Inamura had already
developed the firm's previous foray into four-strokes, the
BSA-like 650cc W1, from a Meguro 500cc K2 vertical twin. And it
was Inamura who would become the project leader for Kawasaki's
N600 750cc engine and then for the Z1's 903cc powerplant.
Still, the question came up at the Z1's
model-introduction press conference in the fall of 1972: Why was
Kawasaki seemingly abandoning its two-stroke heritage to create
this four-stroke? In Cycle magazine's road test of the Z1 in the
November 1972 issue, Kawasaki's Motorcycle Division General
Manager T. Yamada's response was cited: "Lots of reasons, he
said. Kawasaki wanted to build, in their words, the King
Motorcycle, a bike beside which the finest motorcycles in the
world would shrivel in comparison . . . a bike that would leave
a hot and smoking scar across the face of the sport . . . And
you just can't do it, Yamada was saying, with a two-stroke
engine . . . In the first place, Yamada said, the King
Motorcycle must have an engine that sounds right.
"No less important, said Yamada, is the
way the engine looks. Who could imagine a King Motorcycle with
an engine that looked like a two-stroke engine looks, all
crankcases and cooling fins? The King . . . has to have an
engine that looks impressive. And only a big four-stroke is
Another important consideration at the time was the greening of
America—in the face of rising vehicle emissions. Even in 1972 it
was obvious that stinkwheel-powered motorcycles were living on
borrowed time. Besides this, Kawasaki had already done massive
amounts of focus-group research that clearly indicated a big,
four-stroke-powered road burner was absolutely right for the
intended audience—primarily U.S. riders—and for the times.
Nonetheless, it's vitally important to
remember Kawasaki developed the two-stroke 500 Mach III
concurrently with the stillborn 750. That gave the company an
exceedingly high-performance motorcycle to sell as it tested,
retested and refined the Z1, which had its code name changed to
T103 in 1968, then changed again later to 0030; final prototypes
were designated 9057. Perhaps the most famous code name/internal
reference was New York Steak, although one wonders, given
Kawasaki's desire to create the ultimate King of Motorcycles,
that someone didn't dub it Filet Mignon or even Châteaubriand.
Even if it were to be known as
Montmorency, Kawasaki was taking no chances whatsoever with the
Z1's program of testing and refinement. For example, a gaggle of
9057s were shipped to the U.S. in February 1972, where two teams
flogged the horns off the poor, unsuspecting prototypes. Bryon
Kawasaki America's senior test rider, was
joined at Willow Springs and at Talladega Superspeedway by the
company's race team, including Gary Nixon, Paul Smart and Hurley
Wilvert, who cheerfully abused the remarkably stoic motorcycles.
On Talladega's 2.66-mile tri-oval course, they ran the bikes WFO
for the time it took to drain the 4.7-gallon fuel tanks. Testers
also ran some 5000 miles on real roads in this country, going
coast-to-coast-to-coast, Los Angeles to Daytona Beach and back.
After so much development on dynos, roads and racetracks, the
only even slightly unseemly trait the Z1 demonstrated was an
apparent appetite for rear tires and final-drive chains,
consuming the former in about 6000 miles, the latter in roughly
half that distance.
Farnsworth had been working for Cycle magazine when he was
approached by Kawasaki to take on the role of senior U.S. test
rider, specifically for Z1 development. "I was the first
round-eye to ride the Z1," Farnsworth says, "and I was the only
American to go over to Japan to test the bike."
So in 1971 Farnsworth was sent to Japan. Initial plans called
for riding the bike around the vast, 3.4-mile banked oval of the
MITA test track, but those plans fell through. Kawasaki then
found a parking lot and threw out some cones to create an
impromptu "handling circuit."
Farnsworth, who figured he was being paid to tell his employers
the truth with no sugarcoating whatsoever, did so. "The bike
immediately started dragging its mufflers around corners," he
says. "I told them it was a rakuta, or water buffalo in
Japanese." Eventually the testing team made it to a real track,
Tsukuba circuit, but even that was short—just over a mile
long—and not really suited for wringing out the King of
See, at this point in the Z1's development, Kawasaki was deeply
concerned about the bike's durability and reliability, and
rightfully so. Such problems could have not only scuttled the Z1
in the marketplace, but they could have sunk Kawasaki's
reputation as well. Of course Farnsworth knew just where to
go—Talladega Superspeedway. So in late 1972 the entire Kawasaki
Z1–testing entourage descended on Talladega, which they'd rented
for 30 days.
"They were holding it wide open for an entire tank of gas,"
Farnsworth says, "doing about 140 miles per hour." Nothing of
consequence broke, but this was back in the day, before
manufacturers learned something about shock damping and frame
stiffness. "It was a wiggler at the time," he says, "but only if
you let off. If you had the balls and held it wide open, it was
"It took about 10 years for them [Kawasaki, and other
manufacturers] to figure out the steering head was connected to
the swingarm pivot and that you can't put an engine in there
that's going to try to twist the frame apart!"
As a side note, Farnsworth mentions that
the Japanese engineers tended to hang out together—especially at
the hotel at night, after testing was done. No big deal, right?
Except that they were squatting down in a big circle drinking
beer outside a hotel—in the South. Alabama, to be precise. So of
course the Heat swooped in and carted them all off to jail, and
Farnsworth had to bail them out.
But that's not all. From March 13 through 15, 1973 (after the
Daytona 200 had run), Farnsworth brought a full-factory assault
team to beat Suzuki's record set in 1968 of running 90.11 mph
for 2172 miles. Included were Kawasaki's American roadrace team
riders of the day—Yvon Duhamel, Art Baumann and Gary Nixon,
among others—and several U.S. moto-magazine editors, including
Cook Neilson of Cycle and Motorcyclist's own Art Friedman.
Ultimately they slaughtered Suzuki's record, posting a new one
of 109.641 mph for 2631 miles. A special one-off Z1 tuned by
Yoshimura and ridden by Yvon Duhamel set a new record of 160.288
for one lap.
So what was this King of Motorcycles? How was it configured?
What was it really like?
From the beginning, the Z was always all about its overachieving
powerplant. Kawasaki claimed 80 horsepower for the air-cooled,
transverse inline-four—handily about 15 bhp more than Honda's
CB750. Cycle's test described it this way: "Horsepower flows . .
. like water from an Artesian well. It simply never stops."
To further distance the Z1 from the CB750, the Z utilized square
bore x stroke dimensions of 66 x 66mm, rather than the Honda's
old-school long-stroke numbers, to get 903cc of displacement.
When asked why, Kawasaki answered with a shrug, saying, "That's
all it needs." This was a very early indication that the
Japanese manufacturers were no longer interested in archaic,
rigid and limiting class displacements. A sophisticated DOHC
induction system (still rare on mass-production bikes, if not on
Euro performance cars) was fed by a bank of four 28mm carbs.
Down in the crankcases lived a nine-piece, pressed-up,
roller-bearing crank, with caged needle-rollers for each con rod
to ride on —evidence enough of Kawasaki's massive two-stroke
design background. Sufficiently impressive, apparently, for
Cycle to write, "The lower end looks like it came out of a
Porsche Carrera." Power then transferred to a massive, wet,
multiplate clutch and to an equally overbuilt five-speed
transmission. This strength would serve the bike well on the
streets, racetracks and dragstrips of the world for many, many
Although the DOHC system with its shim
adjusters was slightly more complex than the screw-and-locknut
adjusters of most other bikes, Kawasaki tried to make amends by
keeping other maintenance procedures as simple as possible. As a
result, any major top-end wrenching that might be required could
be done with the engine still in the frame.
Where Kawasaki really made a breakthrough, however, was in
emissions control. For instance, sintered valve seats made them
impervious to unleaded fuel, while a low, 8.5:1 compression
ratio ensured the Z's mega-motor could run on the wateriest
swill pumped anywhere in the U.S. More important, though, was
the crankcase fumes rebreather. A canister on top of the cases
and behind the cylinders separated oil from blow-by, then routed
the fumes to the airbox. Absurdly simple, but a scheme claimed
to reduce hydrocarbon emissions a full 40 percent.
By comparison, much of the rest of the motorcycle seemed, well,
conventional. Yes, the stylists managed to make the big Zed
appear slimmer and more lithe than Honda's four-cylinder, but to
quote Cycle once more: "The bike's styling is conservative by
normal standards, and positively funereal by Kawasaki's, the
company that gave the sport laser stripes and lollipop paint
Others, though, felt the Zed was eminently more lustworthy than
the CB750—or any other motorcycle, for that matter. Such
considerations, along with the Kawasaki's crushing performance
advantage, made the bike a smash hit with a bullet when it hit
U.S. dealers' floors in November 1972. Likewise, the press was
just as bowled over.
"The thing that impresses you about the
900 is its great straight-line stability at very high speeds. We
could cruise at 120 mph sitting bolt upright." —Cycle Guide,
"The Kawasaki 903 Z1 is the most modern
motorcycle in the world. It is also the fastest. It is above all
the first of a new generation of bikes, a generation which will
run quietly on the streets of America, a generation which will
attempt to solve motorcycles' tiny contribution to the world's
dirty air; it is the first of a generation of motorcycles which
will come close to being within reason all things to all people,
capable of nattering down quiet country roads packing double one
minute and rotating the Earth with incomprehensible acceleration
the next." —Cycle, November 1972
"The Z1 is one of those shockingly
understated GT machines, the kind on which you can look down at
the speedometer and discover, 'My God, I'm doing 90, I'd better
—Cycle World, March 1973
"A Z1 is the only bike left to which those
famous lines from a mid-'60s road test on a Harley Sportster
still apply: 'It will make hair grow on your chest, and if
you've already got it, it will part it down the middle.' "
". . . the first 903 Z1 four-cylinder had
velveteen refinement and enough performance to place the most
refined gentleman in a state of serious sweat." —Cycle, May 1987
" . . . Kawasaki, like a
black-sheep uncle, has never failed to pat us bad-boyishly on
the head, give us a surreptitious snort from a hidden flask, and
affirm our suspicion that life without suspense is no life at
—Cycle World, April 1993
In short, Kawasaki's 900 Super Four Z1, as it finally came to be
known, was a revelation, a motorcycle that pointed the way to
the future for virtually every other manufacturer on the globe.
The direction was definitely toward performance, but it wasn't
the harsh, demanding type that characterized Kawasaki
two-strokes such as the Mach III and Avenger. Instead, it was a
kinder, more civilized performance—but at an even higher
level—and as inviting and inclusive as the two-strokes felt
hostile and divisive to some.
Even so, the Z1 didn't quite generate the all-inclusive,
big-tent appeal of Honda's CB750. There was still just a bit of
an edge, a subtle feeling of Us versus Them. Where the CB750 had
this wonderful malleable quality that allowed it to accommodate
whatever role the owner had in mind, the Z1 wasn't quite as
obsequious. It's not that the bike wasn't capable of such
shape-shifting; it's just that the Z1's performance (especially
the engine's) was so inviting and user-friendly.
Such qualities guaranteed Kawasaki's Z1 would be remembered as
the motorcycle that ushered in the Superbike era—and cemented
its place in history.