Kawasaki were the last of the
four major Japanese manufacturers to release a turbo-charged motorcycle but
were the only factory to achieve the ultimate turbo ambition - to transform
a medium-sized motorcycle into something as quick as anything around. The
Z750 is the world's fastest production turbo motorcycle - 112bhp at
9,000rpm, a top speed of 146mph and road-tearing acceleration that can cover
the standing quarter mile in 10.9sec.
For many years, turbo-charged
bikes had been the preserve of individual builders, tuners and drag racers,
who adapted big Japanese four cylinder engines with bolt-on conversions for
extra, high-speed thrills. Later Honda, Suzuki and Yamaha produced turbo
bikes, all 650cc and all dismally received in the market. Kawasaki's 750 was
bigger yet lighter than any and an instant, well-acclaimed success. The
others have all been withdrawn, and enhances yet further their
reputation for building large, powerful, bulletproof engines.
On full boost, the
Z750 Turbo shoots, shouts and screams speed.
Where Kawasaki
significantly differed from the other manufacturers was in the design and
location of their turbo-charger unit. They beefed up one of their existing
inline four cylinder engines, the Z750, but instead of mounting the turbo
behind the engine, Kawasaki put it up in front of the cylinders, very close
to the exhaust ports. In a limited space of 7.5in, they managed to run four
highly heat resistant steel pipes from the ports to a collector and thence
to a tiny Hitachi turbo-charger. Such innovative positioning reduced turbo
lag significantly.
The result
is instant response. Running a fairly modest 10.5psi of boost pressure the
Z750 has excellent pick-up and strong acceleration anywhere above 5,000rpm
when the turbo is spinning hard.
The turbo power does not bang in
at a set rpm like many back street, bolt-on turbo bikes. From 5,000 to the
10,000rpm redline, there is plenty of boost and real poke, yet it is
smoothly delivered. The turbo effect is unobtrusive. The acceleration is
unforgettable.
In roll-on tests in high gears,
the Kawasaki will annihilate much larger capacity bikes including its own
big brother, the mighty GPz1000.
The smooth response and excellently rounded
power curve are helped considerably by Kawasaki's digital fuel injection
system. Kawasaki pioneered fuel injection on modern sports bikes and their
computer-linked system, measuring and monitoring engine speed, throttle
opening, intake pressure and engine/air temperature, ensures the Turbo runs
at its best.
The rolling chassis is unremarkable but for the sleek, full
fairing which features an integrated, aluminium frame member. This is a
central section located between the frame's front down tubes which makes the
double steel cradle more rigid, improving stability and protecting the turbo
unit from crash damage. One notable detail can be found in the sealed,
O-ring, final drive chain which is silicone lubricated and has special
cut-outs in every other link to reduce weight and heat build-up.
Kawasaki ZX750E1 vs. Yamaha XJ650LJ
In life we’re faced with choices: republican or democrat, blond or
brunette, paper or plastic? Shopping for a new motorcycle in the early
1980s, you also had to choose between normally aspirated or turbo models.
As the 1980s picked up steam, each of Japan’s Big Four (Honda, Kawasaki,
Suzuki and Yamaha) offered up at least one turbocharged model based on a
standard offering. The train of thought was simple: Combine a 650cc or 750cc
engine with the power boost of a turbo and wham! — big power. For some
shoppers, just the allure of turbo technology was reason enough to buy. And
while each manufacturer (excepting Honda) used the same basic formula
(inline-four engine + turbo = new model), each company’s creation was a bit
different.
To get an idea of what the Turbo Wars netted, we pitted Kawasaki’s
ZX750E1 (also commonly referred to as the GPz Turbo) against Yamaha’s
XJ650LJ Seca. Kawasaki had delivered — albeit unofficially — the Z1-RTC in
the latter part of the 1970s, but the ZX750 turbo was a true production unit
and therefore better suited for this standoff. Both of the chosen combatants
were based on existing offerings, but in keeping with their higher output
mills were better dressed and equipped.
Getting to know them
Following the debut of the original Z-1 in 1973, Kawasaki positioned
itself as a dominant player in the high-performance market. Engines from the
Z and later KZ models routinely found their way into championship-winning
drag bikes and were widely considered to be among the strongest mills
available. With other manufacturers exploring turbo power, adding a
turbocharger was a logical step and created a new high-horse monster for
Kawasaki.
Yamaha’s history was not carved from the same stone as Kawasaki’s, but
the company had a number of diverse machines to its credit. Yamaha’s
legendary 2-strokes and the XS650 twin and XS1100 inline-four earned high
honors among riders on the street, and Kenny Roberts took the Yamaha banner
to the winner’s circle repeatedly during the 1970s.
On paper, the ZX and XJ share a number of similar traits. Beneath their
futuristic body panels they both have a tubular steel chassis carrying an
inline-four engine. The similarities continue: The ZX wheelbase is 58.7
inches; the XJ measures 57.1 inches. Full of fuel and fluids the ZX weighs
556 pounds; the XJ 567 pounds. Seat heights are almost identical, falling
within 0.3 inches of each other with 30.7 inches for the ZX and 31 inches
for the XJ.
But even in their commonality, they are very different machines. The ZX
mill displaces 738cc; the XJ 653cc. That difference in displacement gives
the Kawasaki a 10hp edge over the Yamaha, with a claimed 95hp at 9,000rpm.
This bump in power shows up at the drag strip, with the ZX trumping the XJ
by more than a second in the quarter mile at just over 11 seconds against
the XJ’s 12.68-second time.
A major contrast between the two bikes is their method of fuel
delivery. The XJ uses a bank of four Mikuni 30mm carbs while the ZX features
electronically-controlled fuel injection. This provides the ZX with enhanced
go-juice delivery and seamless response when the throttle is yanked open.
A power-robbing feature of the XJ may be the final shaft drive, whereas
the ZX uses a chain, allowing more of the engine’s power to reach the rear
tire. This choice of hardware may also tell us a bit more about the
intentions of the XJ as a sport-touring mount versus a balls-out performance
ride. The ZX has a pair of discs up front and one at the back, where the XJ
relies on dual-disc front and a drum rear.
On the road
To get these great bikes out on the road, we called in two experienced
riders for their seat of the pants input. In the yellow helmet is Sandy
Callas. With more than 35 years of riding experience under his lid, he
brings a wealth of knowledge to the table, and having owned a bevy of
vintage and modern Japanese machines, he’s a good contrast to
silver-helmeted Ken Rottmann, who takes the other side of the ring. Ken
matches Sandy for riding time, but his interests lean toward the British end
of the pool.
Getting familiar with the bikes, both riders found the Kawasaki to be a
far more aggressive machine in every way, from seating position to throttle
response. Sandy has owned numerous GPz models through the years, and he
found the turbo Kawi similar to the bikes he’s owned, with the obvious
difference of more power. Ken mentioned that the turn-signal cancelling on
the Kawasaki is cumbersome and a bit distracting while in traffic. Maybe
it’s the performance aspect of the ZX’s design that kept it from being as
comfortable, too, but Ken felt cramped in the seat and thought a shorter
rider might feel more at home. Sandy’s overall impression of the Kawi was
about the same, labeling it a sharper-edged machine than the Yamaha. Ken
also disliked the top-of-the-tank location for the Kawi’s gauges, saying
they were hard to read, forcing the rider to take his eyes off the road.
Both riders thought the Kawi’s windshield was too short, providing far less
protection than the Yamaha.
Back in the day, the motorcycling press had lots of praise for the
Kawasaki. "The Kawasaki T-bike is … the quickest and fastest turbo by a
substantial margin. ... Granted, the other turbos are 650s and the Kawasaki
is a 750; nevertheless, when you’re talking horsepower, the numbers win,"
said Cycle magazine in its November 1983 issue. "No
normally-aspirated 750 — and few normally-aspirated anythings — can best the
Kawasaki’s turbo-pressurized acceleration, its headlong rush, its
willingness to leap from 60 to 120 mph in what seems like less time than it
takes to read this line," said Cycle World in March of 1984.
The Yamaha, on the other hand, is a different beast. Ken thought the XJ
felt heavier than it was, but also liked the XJ’s more comfortable
riding posture. Sandy also called the XJ a "softer" machine, but again
admired its comfort. Both liked the wind protection of the XJ, and both
riders suggested it was likely the better sport-touring mount of the
pair, capable of providing comfort and performance over long distances.
Having once owned this exact Seca turbo, I can attest to the bike’s
overall ease of use and comfort when ridden on long expanses of macadam.
Although the Seca was considered docile when out of the boost range,
things get very interesting when you breach the 6,500rpm notch on the
tach. The rush at that point is immediate and urgent, quickly pinning
the ridiculous 85mph speedometer. The Kawi is similarly explosive when
it comes on boost, and the press seemed surprised by the bike. Before
the Kawi, the Honda CX500 Turbo was the only Turbo bike out there, and
most testers found the Seca to be a much better overall package. "The
Turbo Seca transforms itself from motorcycle to superbike and back again
with ease, and the transformation is simply controlled by the right
wrist. No phone booths, full moons or other props are needed," said
Cycle World in its June 1982 issue.
Who wins?
Terrific mirrors allowing riders to actually see behind themselves
combined with easy-to-use turn-signal cancelling add up to more votes in
favor of the Seca. Styling-wise, the Seca uses sharply creased panels
and contrasting graphics for a far more space-age look that some think
has aged poorly. The Kawasaki’s panels all flow as one, leading the eyes
from the nose to the tail in a seamless fashion. The red and black motif
accented by silver panels adds mystique to the overall appearance, and
most think it’s a generally more handsome machine.
Looking them over, it seems that both of these variations on the
turbo theme filled a different niche. The boosted power of the
middleweight engines is a welcome feature on both, but the way they use
and handle their newfound power is what sets them apart.
Ultimately, the insurance industry made it all but impossible for
anyone to afford the required coverage on these puffer bikes, leading to
their premature demise. The engineering, design and function was truly
cutting edge for the day, and that has put them high on collectors’
lists as the market has finally embraced Japanese bikes as something
worthy of attention. Not every model from Japan is loved or coveted, but
the turbos are blowing in strong — just like they perform. MC
