Kawasaki Z750 Twin
Kawasaki Z750 Twin | |
Manufacturer | |
---|---|
Production | 1976 |
Engine | Four stroke, parallel twin cylinder, 2 valve per cylinder. |
Compression ratio | 8.5:1 |
Ignition | Battery, coil |
Transmission | 5 Speed |
Suspension | Front: Telehydraulic fork Rear: Swinging fork |
Brakes | Front: Single disc, 250 mm Rear: Single disc, 230 mm |
Front Tire | 3.25H-19 |
Rear Tire | 4.00H-18 |
Weight | |
Oil Capacity | 2 Liters / 4.2 US pt |
Recommended Oil | K-tech 10W-40 |
Fuel Capacity | 14.5 Liters / 3.8 US gal |
Manuals | Service Manual |
Engine[edit | edit source]
The engine was a Air cooled cooled Four stroke, parallel twin cylinder, 2 valve per cylinder.. The engine featured a 8.5:1 compression ratio.
Chassis[edit | edit source]
It came with a 3.25H-19 front tire and a 4.00H-18 rear tire. Stopping was achieved via Single disc, 250 mm in the front and a Single disc, 230 mm in the rear. The front suspension was a Telehydraulic fork while the rear was equipped with a Swinging fork. The Z750 Twin was fitted with a 14.5 Liters / 3.8 US gal fuel tank.
Photos[edit | edit source]
Overview[edit | edit source]
Kawasaki Z 750 Twin
The first Kawasaki to be offered with disc brakes front and rear, and in 1976 undercutting the price of any similar-capacity Japanese bike on the market, this 750 might have been expected to sell to all. In fact, sales were mediocre; the company, it appeared, were victims of their own publicity which over the years had accustomed motor cyclists to expect only rip-snorting performance from a big bike bearing the Kawasaki name.Cycle Magazine of 1978 If not anything else, the Kawasaki KZ750 is certainly reassuring. What with the sweeping popularity of multi-cylinder street bikes that we have seen in recent years, one might well wonder, "What has become of the vertical-twin streetster?"
This engine configuration enjoyed universal acceptance, once upon a time.
And with good reason, for the vertical twin offered potential simplicity,
reasonably light weight in an engine package of just moderate overall size.
But in the late '60s, things changed. The motorcycle-buying populace, which
for the first time had a large first-time-biker contingent, demanded the
flash and pizazz of many little cylinders all in a row. They wanted bikes
that go hummm, not rumpedy-rump. And they wanted bikes that would not leak
oil. And so, due primarily to the efforts of oriental motorcycle
manufacturers, the public got what it wanted. And what about the Brits and
their venerable Triumphs, BSAs, Velocettes and so on? Well, you might say
they got caught with their spanners down, that and frequent fits of
production paralysis brought about by abusive labor union practices. Poor
guys, they didn't have a chance.
Ensuing years have seen several Japanese attempts at making viable
large-displacement street-touring twins but, with the exception of the
Yamaha XS650, response has been less than frenzied, to say the least. It
seems that when a multi and a twin share the same showroom, the buyer most
often chooses the multi. Presumably, the twin comes off as utilitarian and
dull in comparison to the multi.
So much, however, for faulty perceptions. When the Kawasaki 750 twin made
its debut a couple of years back, it was greeted with a sort of cautious
fascination. Motorcyclists scrutinized the thing in much the same manner as
a cat seeing his first mackerel; he is irresistibly drawn to it by something
deep inside him, yet his unfamiliarity with this new phenomenon makes him
approach it gingerly indeed.
Market response to the KZ750 has been, well, moderate, which is a
disappointment. For it is a machine whose construction, price and
performance make for an excellent package for bikers preferring dependable,
large-displacement, heavyweight mounts. Unluckily, though, it must squat in
the shadows of its multi-cylindered brethren.
In terms of power production, there is at least one basic difference
between the twin and the multi. The multi implements three, four or even six
cylinders as power producing units.
Through using more such units in an engine of, say, 750cc, the smaller
reciprocating pieces can be made to twirl, bump, and stroke relatively
easier than the two large cylinders of a twin having the same displacement.
For example, the inertial problems attendant in controlling a 13-ounce
piston at 8000 rpm are much greater than those stemming from nine-ounce
piston at the same crank speed. Moreover, each gram (about 1/28 ounce) that
can be removed from a valve can affect high-speed valve control
dramatically. In turn, comparatively light valves allow use of cam profiles
yielding closer-to-optimum performance. What all this leads up to is the
fact that the revving multi has inherent high-performance advantages over
the twin.
But don't count the twin dead, for it has advantages of its own,
including less expensive upkeep, relative simplicity and a potential for
excellent performance at moderate crankshaft speeds. And it is within this
context that the KZ750 Kawasaki excels. Furthermore and ironically the
KZ750 powerplant is redlined at 7800 rpm, which is quite high for a showroom
stocker, and testimony that the factors limiting the engine speeds of
yesteryear's twins do not necessarily apply today.
The powerplant is predicated upon a 360-degree crankshaft supported by
four main bearings. This crank layout allows the pistons to ascend and
descend in their cylinders simultaneously, firing alternately.
One objection voiced against the vertical twin configuration is that of
vibration. In the past, engines of this type have been known to wiggle and
shake somewhat. But despite the inherent nature of this glitch, there are
ways to get around it, if not eliminate it entirely: The KZ, for example,
uses a pair of counterweighted shafts, driven by chains, to dampen
undesirable harmonics. One shaft is located in front of the engine, the
other behind it. Some purists might object to the use of mechanisms like
these to counter vibration, citing unnecessary complexity. On the other
hand, however, the counterweighted engine's bits and pieces are not
subjected to so much potentially harmful buzzing and shaking, so,
theoretically, component life should be lengthened despite added complexity.
The KZ750 is not totally free of vibration. The seat transmits a little
high-frequency tingling and the mirrors' images fuzz over above 4000 rpm in
top gear. There is little perceptible vibration from either handlebar or
footpegs. Touring riders anticipating long spells in the saddle can expect
minimal vibration from this mount.
Power output for the DOHC engine is claimed to be 55 bhp at 7000 rpm. How
accurate this is we can't say for sure. But judging from the motorcycle's
quarter-mile performance one would suspect that in reality the motorcycle
delivers 40 or so genuine horsepower to the rear wheel. Mind, this is not to
put down the KZ's performance or engine design. But it is important to put
such things in the proper perspective. Out test bike tipped the scales at a
rather heavy 508 pounds, which makes it one of the heaviest 750 twins
around. No doubt, were 50 or so pounds shorn from the machine, which it
could well afford, all facets of its performance would dramatically benefit.
The engine's power characteristics distinguish the KZ750 from other
motorcycles, while still reminding the rider that it is immutably a twin,
and damn proud of it. In sluggish city traffic the motorcycle never lost its
willing, faithful nature to over-heating, loading up or erratic idling. Low
speed punch is excellent, reminiscent of a crisply tuned TR-6 Triumph; one
of the finest twins made. And even though there is modest fly-wheel effect
to cope with the bike's highish low gear ratio, the bike still can motor
away from a stoplight without undue clutch slipping.
Actually, the only true gripe we have concerning the KZ750's performance
is traceable to those cursed constant-velocity carburetors that it has.
There are two of them: 38-mm Mikunis. These gadgets defy the most concerted
efforts to achieve running smoothness at small throttle openings. Say you're
bustling around your favorite sweeper. You're trying to maintain an
even-throttle mode, wherein you're neither accelerating or decelerating. The
motorcycle is well heeled over, and the last thing you need on this Earth is
a sudden deviation in power to the rear wheel. But this is just what the CV
delivers. Throttle response assumes an on-off nature devoid of smooth
transition between power and no-power. One can only suspect that these
devices are here on this planet only as testimony to mankind's mortal
fallibility. Were these to be replaced with, say, a pair of Dellortos with
accelerator pumps, there is little doubt that all-around throttle response
would improve.
On the plus side of the ledger, we suspect that these same CV carburetors
have a hand in delivering such good gasoline mileage. Our test machine
averaged 46 miles per gallon; a figure including much full-throttle
acceleration through the gears, plus several top speed runs. It is our
suspicion that under ideal conditions 50-55 mph level ground cruising the
motorcycle would deliver 52, maybe 55 mpg.
Factory literature indicates that our KZ750 powerplant produces 43.4
lb-ft torque at 3000 rpm. Such a comparatively low (for motorcycles) torque
peak speed suggests that this machine's torque curve is rather broad, which
is just fine by us. When riding the Kawasaki you get the feeling that the
powerplant is never really laboring no matter what engine revs the
tachometer might indicate. Of course, the CV carburetors are responsible for
some of this behavior, but a thoughtful blend of camshaft profile design and
not over-large ports contribute a lot as well.
Our test bike displayed a surprising top-end punch. When the tach needle
creeps up to 5000 rpm, the rider feels a clearly defined surge of power that
lasts up to just this side of 7500 rpm. At freeway speeds the motorcycle
might just as well be a spirited sporty bike. Indeed, it is at this point the
KZ's performance exemplifies the best characteristics of the
large-displacement vertical twin
Source Cycle Magazine of 1978{| class="wikitable"
|-
!Make Model
|Kawasaki Z 750 Twin
|-
!Year
|1976
|-
!Engine Type
|Four stroke, parallel twin cylinder, 2 valve per cylinder.
|-
!Displacement
|745 cc / 54.45 cub in.
|-
!Bore X Stroke
|78 х 78 mm
|-
!Cooling System
|Air cooled
|-
!Compression
|8.5:1
|-
!Lubrication
|Wet sump
|-
!Induction
|2x 38 mm Mikuni carburetors
|-
!Ignition
|Battery, coil
|-
!Starting
|Electric & kick
|-
!Max Power
|41 kW / 55 hp @ 7000 rpm
|-
!Max Torque
|60.8 Nm / 6.2 kg-fm / 44.8 ft.lbs @ 3000 rpm
|-
!Transmission
|5 Speed
|-
!Gear Ratios
|1st 13.75 / 2nd 9.62 / 3rd 7.50 / 4th 6.14 / 5th 5.25:1
|-
!Drive
|Chain
|-
!Front Suspension
|Telehydraulic fork
|-
!Front Wheel Travel
|146 mm / 5.7 in.
|-
!Rear Suspension
|Swinging fork
|-
!Rear Wheel Travel
|95 mm / 3.7 in.
|-
!Front Brakes
|Single disc, 250 mm
|-
!Rear Brakes
|Single disc, 230 mm
|-
!Front Tire
|3.25H-19
|-
!Rear Tire
|4.00H-18
|-
!Dry-weight
|230 kg / 507 lbs
|-
!Fuel Capacity
|14.5 Liters / 3.8 US gal
|-
!Oil Capacity
|2 Liters / 4.2 US pt
|-
!Consumption Average
|5.1 L/100 km19.6 km/l / 46 US mpg
|-
!Standing ¼ Mile
|14.13 sec / 157.8 km/h / 98.1 mph
|}