The Kawasaki GPz750 makes a good ease for simplicity and
straightforward engineering. Wayne Rainey used a race-hike based on the GPz to
win the 1983 Superbike Championship even though, on paper, the Kawasaki
shouldn't have been competitive with the Honda V-Fours ridden by Rainey's main
competition. That Rainey won is a tribute both to his hard riding and the engine
building ability of Rob and Steve
Johnson and the rest of the Kawasaki
race crew, but it's also a tribute to the motorcycle used as the basis for
Rainey's racer. That tribute is reinforced by a little-expected fact: in
California, in New England, in the South, GPz750s are winning stock-class club
road races and defeating Honda VF750F Interceptors in the process, all
the while remaining reliable and trouble free.
The GPz750 for 1984 is still 738CC with bore and stroke of
66x54mm. The dual camshafts ride directly in the cylinder head casting and act
on bucket tappets set over each valve and spring, and lash is adjusted by
replacing small shims positioned in the top of the valve spring retainer,
beneath the tappet bucket. The cams are driven off the center of the
plain-bearing crankshaft by a link-plate chain. Another, wider link-plate chain
carries power from the crank to output shaft, which drives the wet, multi-plate
clutch through a gearset. The transmission has live speeds and final drive is a
630 O-ring chain.
The GPz breathes through a set of four 34mm Mikuni CV
carbs; the exhaust system is black chrome; and the ignition system is
The dual-downtube steel frame uses a single (damping and air
pressure adjustable) rear shock connected to the aluminum swing arm by a system
of progressive linkages. Wheelbase is 58.9 inch., rake and trail 28
degrees and 4.6 inch. The drive chain is adjusted by moving the rear axle back
in a pair of concentrics.
If all that sounds familiar, it is: The 1984 GPz750 is
essentially the same as the 1983
GPz750. There are a few changes: GPz750s are available in silver paint or the
traditional bright red; the 18-in. cast alloy wheels are painted grey with
polished highlights instead of red with polished highlights; the frame-mounted
fairing has a smooth inner liner; the drive chain is lighter thanks to holes
drilled in the inner link plates, and longer-lasting thanks to new silicone
grease used inside the O-ring sealed rollers.
The handlebar change alone improves riding comfort dramatically, and now the
GPz750 isn't comfortable only at twice-legal speeds. In fact, the new seating
position created by the bars changes the personality and feel of the bike around
town and on the highway. Without the distraction of aching wrists and shoulders
caused by the 1983 bars, the rider notices how good the Kawasaki's suspension
is. In normal use, the Kawasaki is a comfortable motorcycle.
If one word can be used to describe the GPz's handling at speed, under
pressure, it is stable. That stability is especially noticeable in fast, bumpy
sweepers, and the Kawasaki never shakes its head or wobbles or varies direction
without the rider's explicit command. If there is a price exacted for that
stability it is a slight loss of agility, of quickness of response. But unless
the GPz is ridden right before or right after an Interceptor or GS750 with
16-in. front wheels, the rider will never notice anything except that the
Kawasaki goes around corners with stable precision.
The bike has good top speed, too, although reaching that speed takes more
than a half-mile: our 1984 test bike reached 123 mph in the measured half-mile,
down two mph from 1983. But given enough room, the Kawasaki will redline fifth
gear, reaching 136 mph.
The Kawasaki's best quarter-mile time on a less-than-perfect day was 12.43
sec. with a terminal speed of 106.25 mph, slower than our 1983 test bike's 12.13
sec. at 109.48 mph. The Kawasaki makes good peak power, a claimed 85 bhp at 9600
rpm, but the power band has a big bulge above 7500 rpm and lacks the mid-range
power of the Suzuki or Honda 750s. The power distribution is most apparent
coming off stoplights or pulling around slower traffic on the highway; a fast
launch takes a lot of rpm, and a fast pass takes a downshift or two depending
upon the initial cruising speed. The GPz turns 4400 rpm at an actual 60 mph
(indicated 60 is an actual 55 mph).
At that speed—and at every other engine speed—the Kawasaki is the smoothest
750 on the road, thanks to rubber front engine mounts. There's no resonance in
the bodywork, no buzzing grips, no blurred images in the fairing-mount rearview
mirrors (although those mirrors do show too much elbow and sleeve and not enough
The Kawasaki's gauges are a combination of simple and -tech, conventional and
unusual. The speedometer is straightforward, reading to 150 mph with built-in
odometer and resettable trip meter. The tachometer is smaller, perhaps
two-thirds the size of the speedometer, and doubles as a voltmeter if the rider
pushes and holds down a button on the instrument mount panel. Flanking the
upper-triple-clamp-mounted ignition and fork lock switch are small pods
containing warning lights for turn signals, high beam, neutral, and headlight
failure. There's also a red light that flashes if the fuel or battery fluid
level is low, if oil pressure drops or if the sidestand is down. To see which
problem the light refers to, the rider must look down at an LCD display panel
mounted on the top of the gas tank, ahead of the gas cap. The fuel gauge is a
sort of bar graph - the more bars show, the more fuel there is in the tank. The
split location of the gauges and the instruments isn't universally popular -
some riders hated it.
Where our test Kawasaki shone was in braking. It needed just 119 ft. to stop
from 60 mph with perfect control and excellent feedback through the firm
handlebar lever. The anti-dive system, which increases compression damping to
slow fork compression under braking, is controlled by a valve activated by brake
fluid pressure. The system is adjustable, with four settings selected with a
plastic knob on each fork leg, but even at the firmest setting the system has no
noticeable effect. That obviously didn't hurt the braking.
The Kawasaki's Dunlop tires - a 110/90-18 F17 front and a 130/80-18 K427rear
- are among the best original equipment tires and work well with the responsive
brakes. They're fine for vigorous street riding as well, holding well and
delivering good tread mileage too.
Astute readers will no doubt remember that when we compared the 1983 Honda,
Kawasaki and Suzuki 750s, the Kawasaki came in third in just about every measure
of performance. The test didn't show the Kawasaki's long-term durability and
response to easily-performed, class-legal modifications.
It seems that adding five or six teeth to a GPz750's rear sprocket, a good
valve job, second-oversize Kawasaki pistons and strict attention to minimum
factory specifications for cylinder deck height all work wonders for a Kawasaki.
The fact that the Kawasaki is easy to work on encourages its modification,
unlike the Honda and its cast-into-the-crankcase cylinders.
So it is that a two-valves-per-cylinder, air-cooled GPz is able to run with
and defeat a four-valves-per-cylinder, water-cooled VF750F and a
four-valves-per-cylinder, air-cooled GS750 on the road race track.
Compared with the rest of the class, then, the Kawasaki is geared tall, which
hurts dragstrip and roadrace performance (at least until the sprockets are
changed by the owner) but helps mileage. On our mileage test loop, the Kawasaki
returned 52 mpg.
Which brings us to a small disclaimer. The machine seen and tested here is a
49-state model. Bikes brought into California in 1984 must have a charcoal
cannister system for capturing unburned hydrocarbons vented from the gas tank
and carburetors. Kawasaki positions its cannisters in the tail section and
routes hoses from the carbs and tank vent to the cannister. The entire system
adds a pound or two to the bike's weight, Kawasaki representatives tell us, and
doesn't affect performance. But our test bike wasn't fitted with a cannister.
As delivered, Kawasaki's GPz750 isn't as fast nor as quick as a Suzuki or
Honda 750, but riders who don't race and don't ride Suzukis and Hondas
back-to-back with a Kawasaki will never notice the differences in power
delivery. It is smooth, reliable and responds well to minor modifications to
increase power. Because it isn't the quickest and fastest 750, the GPz is
discounted in many states, making it a high-flash bargain. But discounted or
not, the GPz750 is capable of giving its rider a lot of trouble-free fun.
Source Cycle World 1984