Numbers matter, even subtle numbers. Like the difference between 1,015cc and 998cc. Arriving at the smaller number meant decreasing the bore on Kawasaki’s 1980 KZ1000G from 70mm to 69.4mm on the 1981 KZ1000J. In addition to this minor adjustment to meet racing rules, just about everything else on the motorcycle had been changed as well, with the exception of the 66mm stroke.
Let’s go back a bit, to late 1972 when Kawasaki introduced the 903cc Z-1—the Killer Kaw, later labeled the KZ900 in 1976. It had a perfectly equal bore and stroke, 66 by 66mm, which was then bored out 4mm in 1977 to make the 1,015cc KZ1000A, maintaining the KZ’s reputation as the biggest, strongest UJM on the market. But the competition was getting fierce. Move up to 1981, and the new J model was an absolute delight—a street bike with Superbike potential. When the boys at Akashi, Kawasaki’s brain center, were given the task of revamping the 1,015cc KZ, the company’s bread-and-butter bike, they did it with gusto. It may have taken them a couple of years, but it was time well spent.
First, as always, more power. They lightened the crankshaft by hollowing out some bits, used a pork-chop flywheel rather than the previous full-circle design, and in the end shaved 4.9 pounds off the weight. Bigger valves went in the two-valve heads, and bigger, lighter, aluminum-bodied 34mm constant-velocity Mikuni carburetors were fitted. They fiddled with the camshaft timing so more gas could be stuffed into the combustion chambers and compressed 9.2 times. End result: almost 25 percent more horsepower, from 83 to 102 at 8,500 rpm. Mind you, those were Kawasaki numbers probably taken off the crankshaft, as the rear-wheel determination was more like 80 horses.
Ignition was by CDI, and anybody interested in the history of capacitor discharge ignition should go back to Nikola Tesla’s patent No.609250, filed in 1897. All agree that this modern electronic arrangement was far better than previous ignitions, especially with multi-cylinder engines. Exhaust used a four-into-two system, with a muffler on each side of the rear wheel.
Primary drive was by straight-cut gears, efficient albeit a bit noisy, and an extra plate was added to the clutch. Five gears moved the power along, from a 12.5 first-gear ratio to 4.9 fifth. No kickstarter was included, as riders now understood that the electric leg was very reliable. The output shaft was beefed up, and a new #630 chain with a breaking strength increased by more than 1,000 pounds went to the rear wheel. Chain technology development was going gangbusters at this point, as engines were generating more than 100 very stressful horsepower.
Second, the chassis. The diameter of the steel tubes in the frame was increased for better cornering rigidity, while the wall thickness was reduced. Stiffer frame with less weight; good thinking. The steering head, now using tapered roller bearings, was strengthened with two gussets and had a rake of 27.5 degrees, an increase of 1.5 degrees over the previous model. According to the spec sheets, wheelbase was 59.8 inches.
The front fork was enlarged to 38mm, and anti-stiction bushings were at top and bottom. It had 5.7 inches of travel and was air-adjustable, operating with a modest 7 psi for street use, 13 psi when getting enthusiastic. The pair of rear shock absorbers (the photo bike has a pair of aftermarket piggyback Öhlins) had a lot of adjustability, with seven positions for spring preload, five for rebound damping and almost four inches of travel. Seven-spoke aluminum alloy mag wheels used a 110/90-19 tire at the front, 120/80-18 at the rear. A pair of 9.3-inch discs up front were squeezed by single-piston calipers, as was the similar-sized disc at the back.
Third, rider comfort. This was not a racer, but a sportbike intended for the weekend rider—who might well want to put a few hundred miles on between Saturday morning and Sunday evening. To this end the front of the crankcase was rubber mounted to the full-cradle frame, eliminating much of the inevitable vibration. Handlebars were at a useful level, allowing for comfortable riding during this 55-mph era. (For all you young ’uns, back in 1974 the feds were worried about our consuming too much gasoline and imposed a national maximum speed limit of 55 mph, an excellent example of congressional incompetence.) Up front a speedometer, fuel gauge and tachometer were very readable, with the speedo going as high as 85 mph—when in fact 135 would have been more truthful.
A pleasantly large gas tank held 5.7 gallons, good for more than 200 miles, and the long, flat saddle was built to keep a rider happy for many hours. We don’t know what effort was put into shaving ounces off the body panels, but the J model ended up 30 pounds lighter than the previous G.
Choke if cold, turn the key, push the button and a very melodious sound emanated from the mufflers. An average rider would certainly enjoy his or her day in the saddle, while a more competent person would like the extremes to which the J could be pushed.
In 1981 Eddie Lawson won the AMA National Superbike Championship on an admittedly much modified KZ1000J, and Kawasaki decided to build a look-alike version, the ELR or Eddie Lawson Replica. This KZ1000R, advertised as a “street-legal superbike replica,” was offered to the masses for a few hundred dollars more than the $3,800 J version. The ELRs had a little nose-fairing, sophisticated Showa shocks and a black 4-into-1 Kerker exhaust.
Kawasaki also built 30 real-racer versions to sell to qualified racers, which were certainly not street-legal. These KZ1000R-S1 models cost a hefty $11,000.
Then the ZX bikes came along, and the only KZ1000 left was the police version—which could still pull over a speeding motorist with ease.