(This Retrospective article was featured in the July 2012 issue of Rider Magazine)
Story and photography by Clement Salvadori
Year/Model: 1981 Kawasaki KZ750-E
Owner: Franco Teti, Los Osos, California
Class distinctions by engine size are important, and are often delineated by the numbers on a motorcycle’s side covers.
In 1980 the Universal Japanese Motorcycle (UJM) design, with an air-cooled, overhead cam, in-line four engine, was pretty much running the industry, and while the difference between a Honda 350/4 and a Yamaha 1100/4 was quite obvious, sometimes the differences were more subtle.
Kawasaki had never been one to follow the crowd. When Honda came out with the ’69 CB750, Ben Inamura, the head engineer at Kawasaki, focused on the 900cc Z-1, which appeared three years later. And then he developed the KZ650/4, with a bore and stroke of 62 by 54mm, for 652cc total. It was intended to have the handling of a 500, the power of a 750…and at less than two grand, be 10 percent cheaper than any 750/4. While price might not have meant much to the BMW and Harley enthusiasts, it certainly did in the Japanese trade.
The 650 worked for a couple of years, with the aftermarket helping things along by offering all sorts of hop-up equipment. But by 1979 the 750 class was by far the most popular, and 100cc was a lot to give away, so Inamura decided that he was going to have to go 750. This was to be no big redesign—no 16-valve heads, no new chassis—the KZ750 would simply be a bigger, better KZ650.
Just to clarify things, in 1980 Kawasaki had two very different KZ750s—the KZ750-G parallel twin, the engine of which had been on the market since 1976 (Retrospective, December 1996), and the new in-line four, known by the postfix E.
Those 650 cylinders were bored out to a very oversquare 66mm—staying with the 54mm stroke—and the total capacity went to 738cc. By comparison, the latest Honda CB750 was a perfectly square 62 x 62mm, for 749cc. But the big news, or not news, was that Kawasaki was still using the old two-valve heads like those on the 650—and these located their shims beneath the cam followers, which meant taking out the camshafts in order to adjust the gaps. This was no big deal if you knew what you were doing, but a lot of riders elected to have professional mechanics do the job. Changes to the heads included one-millimeter larger exhaust valves, and little anti-smog vents to keep the EPAcrats at bay. This minimalist trick allowed oxygen to flow into the combustion chamber and mix with any unexploded hydrocarbons, creating carbon dioxide that was on the approved list of emissions.
This anti-pollutant gizmo did not seem to harm performance. The KZ650 knocked out close to 50 horsepower, and adding less than 90cc made the dynamometer show more than 60 horses at the rear wheel, with peak ponies coming at 9,500 rpm. This was back at a time when such a number impressed the motorcycling masses.
The major changes, other than the bore-out, were the
bolting on of 34mm Keihin constant-velocity carburetors, and the use of a transistorized ignition. An interesting tidbit is that this new four-banger was first introduced in South Africa, a relatively small market, but obviously with the intent of allowing the bike to be consumer-tested before releasing it to the United States and Europe. Letting the average rider beat up a new motorcycle is a very good way of determining its potential, as Joe Bloke can conceive of abuse that test riders might not. Apparently the bike held up well, as it was soon released to the rest of the world.
Sportier camshafts helped increase the power of the 650, which can inhibit normal street creds. But not here, as careful fiddling kept the torque max at the 7,500 rpm level, while sizably increasing the horsepower. Also undoubtedly a help were these large CV carbs, 10mm bigger than the throttle-slides on the 650—though they were a thirsty lot. Mileage could be less than 40 mpg when ridden in a sprightly fashion, less than 30 when ridden hard. If economy was on the rider’s mind, he could buy the KZ440 twin.
Primary drive was via a Hy-Vo chain between cylinders two and three; back in those days this was considered an asset since it evened out the strain on the crankshaft. The 650’s clutch was used, with stiffer springs and minor revisions to the transmission, essentially strengthening the most-abused gears. And the final-drive chain went from a 530 to a 630. But the total weight of the bike went down a couple of pounds…brilliant. Curb weight was a shade under 500 pounds.
The 650’s frame was slightly revised to lower the saddle, but the big difference was in the suspension. An air-adjustable Kayaba fork provided almost six inches of travel, with the firmness up to the rider. Angle was 27 degrees, trail 4.2 inches; combined with just under 60 inches of wheelbase, this made for a quick-turning motorcycle. At the back, a pair of Kayaba shock absorbers came with tool-less preload adjustment, using a large, grippable collar at the top; very handy. These allowed four inches of axle travel. Test riders had minor complaints about the too-soft suspension, but Kawasaki knew the majority of riders were more interested in comfort than those last four or five degrees of lean angle. And the racing-inclined could make their own modifications.
Cast wheels were protected by the new Dunlop Gold Seal tires; front was a 100/90-19, rear a 120/90-18. Triple 10.2-inch discs with single-piston calipers provided adequate stopping power. Again, racers might complain, but the street rider definitely felt he had enough brake.
Throw a leg over the saddle and settle in. Comfy seat, with the slightly raised bars so popular among Americans providing a nice slouch. Ignition on, push the button and the two mufflers kept the noise muted. These were the same mufflers as found on the 650.
Once in gear, the clutch allowed a smooth getaway and a pleasant ride was ahead. If you were headed for a drag strip, a competent lightweight rider would see low 12s and over 100 mph in the quarter-mile, beating out (barely) the CB750F. But the prices of the two were now pretty equal, with the KZ at $2,750, the CB at $2,850. You pays your money and you takes your choice.
Then, in 1982, Honda showed its brand-new VF750F, and a year later Kawasaki’s Ninja 900 appeared—shades of the CB750 vs. Z-1 900. Does history repeat itself?