SUZUKI MOTORCYCLES GSXR 750 K1
Gsxr 750: welcome back to literland
 
Mat Mladin and Yoshimura's success in capturing the AMA Superbike crown in 1999,
together with extremely strong sales of both the Gsxr 750 and the new, right-size 600,
was evidence that Suzuki's engineering staff and market planners made the right
decisions in returning to a light, elemental sportbike for the generation that arrived
in 1996.
Given such success, Suzuki moto might have chosen to rest, to give the engineers and
designers a day or two off and bask in the glory.
Many other manufacturers have done so,
allowing a groundbreaking product to soldier on with minor updates for several product
cycles.
 
The danger in that approach, though, is not just the risk of being overtaken by
the competition but also the real possibility that it will cost more to jump back into
the fight from a weak position than it would to keep the pressure on.
Suzuki moto, most emphatically, did not rest.
Scarcely halfway through the previous bike's
production run, Suzuki moto began work on the 2000 Gsxr 750 with a few simple goals: make it
lighter still (having rediscovered the benefits of low mass all over again), make it
faster, and make it handle better.
  Considering the dramatic improvements of the 1996-'99
models over their predecessors, a big leap would not be possible.
Already, the Suzuki Gsxr led
the category in high power and low weight, and it didn't look like anyone else was ready
to jump back into the 750 cc class.
Indeed, Kawasaki continued to race the ZX 7 R but did
not lavish any development on the street version.
Yamaha had long since left the class,
and Honda remained with only the sport-touring VFR, because the new RC 51 was in place
for AMA Superbike and World Superbike competition.
With the V-twin Tl 1000 R racing project shelved, Suzuki moto continued to push the Gsxr 750's
capabilities for racing for the elite level, as well as to improve chances for the many
privateers who campaigned the Gsxr in Supersport and Superstock racing.
  Even as the
market continued to push for a two-class sportbike hierarchy-600s and 1000s-the company
remained true to the 750. "Many times [the product planners in Japan] asked abQut the
possibility to stop making the Gsxr 750, but I was firm with them.
It is our heritage and we
will continue," says Motoo Murakami, executive vice president of American Suzuki and the
former head of Suzuki Germany, a key man in developing corporate strategy.
Suzuki's penchant for doing more with less-combining technologies and sharing parts and
development time among several motorcycles-was about to rise again.
  Along with the new
Suzuki Gsxr 750 came the predicted Gsxr 600 replacement based on the same platform, released a
year after the Gsxr 750 to keep one from stealing the other's marketing push.
There was also a surprise.
A big surprise. But we'll get to that later.
As always, Suzuki moto favored development of the Gsxr 750. It's natural. "We produce what we
race" is something of a corporate mantra, and at the time AMA Superbike and World
Superbike were both in the 750 cc fours/1000 cc twins format.
Suzuki moto then strove to
produce an improved Gsxr 750 that would also make a competitive 600-no small feat in
itself-and that could grow into a worldbeating 1000.
But the Gsxr 750 came first, bristling with new technology.
  In the search for lower weight
and more power-delivered together to make improved performance, as ever-Suzuki revised
the chassis, comprehensively reworked the engine, and added a new fuel-injection system
that would, once again, cause the other manufacturers to take notice (and, to a great
extent, to follow the same technological path).
In the end, the new Suzuki Gsxr became the
lightest in the model's history-365 pounds dry, compared to the 395 of the original.
And
it was the most powerful: while riders were enthralled with the 1999's 114 horsepower at
the rear wheel, the 2000 model was better by 10 hp.
Barn! Just like that.
Starting with the chassis, Suzuki moto once again tried to compact the motorcycle. (In fact,
with some hindsight we can see this trend, which started with the '96 model, continue to
play out. Each generation since the '96 had become smaller, lighter, more efficiently
packaged. Even the 1000.)
  The 2000 model was nearly an inch shorter overall and a
quarter inch narrower. The frame, though similar in appearance, was completely revised.
It was shorter-the vertical distance from the bottom of the steering head to the
swingarm pivot was reduced half an inch, while that measurement horizontally was trimmed
0.3 inch.
The height of the stamped-aluminum main spar was reduced 0.3 inch, as well.
Components were juggled; the crosspiece below the swingarm pivot that holds the lower
shock mount was changed from an extrusion to a casting to save weight, which was
partially offset by a new cross brace between the vertical ears supporting the sub frame
and internal bracing between the massive swingarm-pivot casting and the main side spars.
The overall goal was increased rigidity, better crash tolerance, and reduced weight.
Overall, the frame changes helped cut 4.4 pounds.
  Suzuki's racing success with the Gsxr 750 and broad customer acceptance caused the
engineers to stick with the previous bike's general chassis dimensions. Rake remained at
24 degrees and trail at 3.8 inches, but the wheelbase grew 0.6 inch thanks to a longer
swingarm that itself was significantly reworked.
Still braced, the massive forward deck
was slimmed, while the lower cross bracing just in front of the tire was increased in
size.
A new aluminum-body shock from Showa saved a pound all by itself despite having a
larger, 46 mm damping piston. It's not everyday that you get a better piece - improved
damping and durability - and have it weigh less, too.
Up front, the Gsxr 750's showa fork was revised, with more travel but less overall
length, and placed in triple clamps 0.3 inch (7 mm) narrower. The top stem nut was
changed from steel to aluminum.
  Bolting to this inverted fork were new brake components,
a step back to four-piston calipers from the '99's six-piston versions. Together with
lighter front discs, the brakes alone were responsible for nearly 2 pounds of lost
weight. (The rear brake received an aluminum piston for reduced weight.)
Even the wheels
came in for scrutiny: new, diamond-shaped spokes, a smaller 5.5-inch rear wheel wearing
the now-standard 180-cross-section tire, and a redesigned sprocket/ cush-drive setup
slashed 3 pounds from the bike.
The new bodywork-clearly still a Suzuki Gsxr but usefully modernized-also contributed to the
weight-loss program. The fairing panels were thinner (2 mm vs. 2,5 mm on the '99) with fewer
parts.
The twin-bulb headlight assembly used a single reflector and saved weight over
the 1999s, and it moved the leading edge of the ram-air ducts closer to the center of
the bike, for improved efficiency. Here again you can see Suzuki's wind-tunnel work
arriving in the showroom.
Moving on to the engine: you could be excused for assuming, at a glance, that the 2000
bike's engine was a carryover item. In fact, it was almost completely new. Retaining the
double-split crank-case-the crankshaft and transmission shafts are carried on two
planes-the 2000 engine's bottom end was reworked to move the transmission shafts closer
to the crank for an overall reduction in engine length.
The upper part of the crankcase,
which had been two pieces in the previous Gsxr 600 and Gsxr 750, was now one, following what had
become industry convention.
With this change, Suzuki moto deleted an external hose that
provided oil to the top end and replaced it with an internal gallery, saving weight.
Although the engine retained the previous 72 mm-by-46 mm bore and stroke, the pistons were
forged instead of cast aluminum (thus lighter and stronger), and the wrist pins had
tapered bores for yet more weight reduction.
Lighter pistons permit lighter components down the line; the connecting rods (now
shot-peened for strength) were thinner and gripped 1 mm-thinner main journals. The crank
was reduced in size a millimeter here and a millimeter there.
Even the cams came in for a weight reduction, with a larger inner diameter. They rode in
a new head with reduced valve angles-now 25 degrees compared to 29 for the '99 bike-for
a more compact combustion chamber and straighter intake ports.
The valves remained the
same size but were closed by single springs for 2000 and had thinner stems.
By careful
development of the head layout, it was no taller than before. Slightly smaller chambers
netted an increase in compression ratio to 12.0:1 (up from 11.8:1). A side note on the
head design: it now carried internal passages for the PAIR (pulsed air injection)
emissions system.
Before, external lines led to flanges just above the exhaust port on
bikes built for certain markets, such as California.
But with emissions regulations
becoming stricter, all bikes would need some kind of air injection.
To simplify hardware
and save weight overall, Suzuki moto made the change to the head casting. It slightly
complicated the casting and machining of the head, but it simplified the number of
external components and reduced assembly time.
All of these engine changes may seem minor in terms of producing horsepower, but they
contributed to the whole and allowed maximum advantage to come from the Suzuki Gsxr's improved
induction and exhaust systems.
The all-stainless four-into-two-into-one exhaust system
wasn't much different except for a shorter muffler. But the injection system was all
new.
"I was originally told that this idea was not good and not to pursue it," says Kunio
Arase of his concept for the Gsxr's unique twin-throttle-valve injection system. "But I
felt it was a good idea, so I continued to work on it in my spare time and on weekends."
Good thing he did.
At its introduction, the Gsxr's new injection was lauded as a great
step forward, making electronic injection feel more like a set of well-calibrated
carburetors. (Many riders disliked the instantaneous response of modern injection, which
could really upset the chassis during hard riding, particularly with a high-performance,
light-flywheel engine.)
The key to this system was in maintaining good air velocity in the intake ports.
With
traditional single-throttle injection, when the rider whacks open the throttle the air
can nearly stagnate, causing a stumble. The slide on constant-velocity carburetors was
designed to prevent this condition by partly blocking the intake tract and maintaining
good velocity. But CV carbs can only react to intake flow, and they can sometimes be
fooled.
Jetting was a fine art.
In Suzuki's new system the secondary throttle valve resides just upstream of the
rider-controlled throttle. The engine-control unit manages it with settings based on
dyno testing. It cannot be fooled.
At the same time, the throttle bodies were revised
with slightly larger outlets (on the engine side) and inlets (near the airbox) but
slightly smaller (42 mm vs. 46 mm) throttle plates.
The injectors were re-aimed to set at
60 degrees from the main throttle-body axis instead of 32 degrees, so that the fuel
spray hit the wide-open throttle plate at maximum power to help promote atomization of
the fuel.
Before, the fuel did not come into contact with the throttle plate.
This double-throttle system was managed by a new, lighter (of course), more powerful
computer that held eight distinct injection maps-two for each cylinder, one for light
load, and one for heavy load.
The computer decided which to use based on throttle
position, engine rpm, intake vacuum, and other parameters. At light load, the computer
read the intake vacuum for a more precise indication of throttle position.
At high load,
it excluded this input and relied on throttle position and rpm. The system also took
into account vehicle speed, ambient pressure, coolant temperature (mainly for cold
starting), and cues from the side stand and tip-over switches.
A new airbox fed this system, as well. The secondary throttle plates had the added
benefit of reducing intake noise-especially during the official emissions tests-so the
flapper valve used in the '99 model could be eliminated. (More weight savings.) The
Gsxr also regained its renowned intake honk.
When you think about the state of affairs in 2000, it's still amazing that Suzuki
moto lavished so much effort on the Gsxr 750, even if you knew a reworked Gsxr 600 was coming. In any
event, the new Gsxr 750 sparked a new round of appreciation for the class.
"I don't mean to take anything away from the original Gsxr 750," explains Paul Dean,
editorial director of Cycle World magazine. "But the 2000 model just got everything
right.
It was fast, great handling, and gave me tremendous confidence. I think that bike
was a true high point of the Gsxr 750's development."
"The 2000 model was a major surprise, given that all the other manufacturers had
basically left the 750 class," says Kent Kunitsugu, editor of Sport Rider. "The jump in
performance was almost as great as the '96 model's progression, which surely took a lot
of R & D resources that other companies would have diverted to 'more important' (read:
'better selling') models. It's pretty obvious that the Gsxr 750 is a matter of
corporate pride to Suzuki moto. But for good reason: they are justifiably proud of the fact
that the original Gsxr 750 was the bike that started the 'racer-replica' revolution."
In its first year, the fifth-generation Gsxr was as strongly praised as the original.
It won numerous bike-of-the-year awards and often placed extremely well in competition
with open-class machines.
Motorcyclist magazine named the Gsxr 750 the Motorcycle of the
Year in 2000. It won Cycle World's Best Superbike award that year as well. When tossed
into comparisons looking for ultimate handling and performance, it usually won outright.
Mat Mladin took the AMA Superbike crown again in 2000-albeit on the 1999 bike because
the new model had not arrived in time for necessary testing before the season began.
Once again, Suzuki moto dominated the stock classes and were the bike of choice for
privateers.
And yet there was more to come.
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