It often seems that the more things change, the more that they stay the same. In the case of the rapid changes that followed the decade after the introduction of the 1969 Honda CB750 Four, it’s remarkable how superficially similar were the offerings from the Big Four Japanese Motorcycle makers.
At the beginning of the 1970s, the premier class motorcycles were a mix of two- and four-stroke twins and triples plus the Honda CB750. Within a decade, they were all four-cylinder four strokes of 750-900cc. What would be coming next? Interestingly, the new UJMs of the early 1980s showed how the niche had converged mechanically but diverged cosmetically. Typical of the machines that made up the class in the early 1980s were the Honda CB1100F, Kawasaki KZ1000 MkII, Suzuki Katana 1100, and (though a year or so later) the Yamaha FJ1100.
The sweet spot for capacity was 1000-1100cc; air-cooling was still in vogue, and double overhead camshafts were “de rigueur.” Liquid cooling and fuel injection would come later. And the Big Four’s UJMs followed similar recipes: all were double overhead camshaft in-line fours with five-speed transmissions, engines mounted across the frame with chain final drive. All employed four valves per cylinder — except Kawasaki, which stuck with two valves for each pot.
And while it may be easier to spot the differences than the similarities, all four shared a common general architecture, similar technology, and performance. Interestingly, both Suzuki and Kawasaki retained the built-up crankshafts and roller-bearing bottom ends found on their other earlier fours. Why? The answer is in both makers’ two-stroke heritage.
Suzuki’s switchblade: 1981 Suzuki Katana GSX1100
Fashion is a cruel taskmaster, it’s been said, and nowhere does this apply more than in motorcycle design. Remember all those easy-rider clones with stepped seats, raked-out forks, and the rest? Can’t give them away now. And the more radical the design, the faster it fell from favor. So when Suzuki adopted Hans Muth’s razor-edge styling for the 1981 Katana 1100, it was a calculated gamble with a time limit.
Fashion aside, the Kat’s fairing offered aerodynamic benefits from a lower profile than the preceding GSX, offering a reduced drag coefficient. These factors meant 140mph out of the box with the rider prone. If the pilot sat up, though, the extra resistance could release some unpleasant wobbles, though they were mitigated by the Katana’s long wheelbase and relatively lazy 27-degrees of rake. Sidewinds had a similar result, but the fairing was redesigned to minimize the effect. And while the riding position was racy, rider reports noted the pilot’s overall comfort.
Below the bodywork was Suzuki’s latest iteration of their air-cooled four-valve in-line across the frame powerplant, now with “TSCC” (twin swirl combustion chambers) to optimize fuel efficiency; and the aforementioned built-up crankshaft running on ball and roller bearings. (The Katana was also available using a 1,000cc engine with flat slide Mikunis for production racing, the GSX1000S.)
Typical for the time was the dual cradle frame, but with the addition of an anti-dive front fork. This worked by moderating the fork oil pressure under load and avoided having to stiffen the suspension, a low-tech remedy for fork dive. It also had the benefit of reducing unwanted headlight dip under braking. Rear spring/damper units were adjustable — four ways for damping and five for preload. The triple disc brakes were reported as effective, if a little too liable to lock at the front. Regardless, the Katana and its signature knife device acquired something of a cult following with both reviewers and buyers. That said, the air-cooled four was becoming stale-dated: in late 1984, the new GSX-R motor was introduced with SACS (Suzuki Advanced Cooling System) air/oil cooling.
“The styling is a poseur’s dream,” wrote Australian Motorcycle News, “The Katana is the shape of things to come. So, even if you don’t like the styling, I’ve a feeling you’ll have to get used to it.”
Supersport smoothie: Yamaha FJ1100
The most bodacious bodywork of the early streamlined sportbikes belonged to the 1984 Yamaha FJ1100. Its frame was even designed with front-end plastic in mind. Along the way, the FJ1100 effectively drew the blueprint for a generation of Yamaha sport-touring motorcycles right up to the FJR1300.
Rather than simply revising its 1970s-era XS1100 motor, Yamaha opted for a new air-cooled engine with five gears, from which Yamaha engineers extracted a class-leading 125hp. The FJ also marks a split in superbike development, paving the way for a new class of liter-plus sport tourers, leaving the out-and-out sportbike competition to under 1000cc bikes, 750s per AMA’s Superbike racing rules beginning in 1983.
Minimizing engine width was a primary objective, so the generator went behind the crankshaft, and drive to the gearbox input shaft was by means of a gear straight-cut into the number three cylinder’s crankshaft web. The result was an overall engine width of just 20.6 inches. Behind the crankshaft in the same casing was the multiplate diaphragm spring wet clutch and five-speed transmission. Yamaha engineers were also able to keep the engine compact enough for a 59-inch wheelbase.
Less conventional was the chassis. Built from rectangular section steel tubes, the frame’s upper members curved around the engine instead of over it, heading for the swingarm pivot area. The top tubes continued forward around the headstock and triangulated to it. The result was an extremely rigid front end.
A sturdy rectangular extruded alloy swingarm attached to a single spring/damper unit, as pioneered by Yamaha: Monocross rear suspension. At the front was a conventional telescopic fork, fitted with an adjustable anti-dive device using hydraulic pressure from the front brake line to restrict fork travel. So the fork would compress normally when hitting a bump in the road, but its compression would be limited when the front brake was applied.
There’s no question the FJ’s performance was at least as good as its contemporary competition. It managed to be wickedly quick, yet docile in traffic; adept at track sessions, yet equally at home on tour.
The FJ1100 certainly caused a stir: “The best large displacement sport motorcycle of 1984, and maybe even the best in its class in the history of motorcycling,” said one enthusiast magazine, while another made the FJ1100 its Bike of the Year, and yet another raved, “All hail Yamaha’s FJ1100, King of the Superbikes… class champ, no contest.”
The outlier: 1979-80 Kawasaki KZ1000 MkII eight-valve
The Z1000 MkII was something of a stop-gap measure for Team Green. First into the liter class with the KZ1000 and Z1-R, Kawasaki then lagged behind its rivals, foregoing a switch to a four-valve cylinder head. Yamaha, Suzuki, and Honda all featured four valves per cylinder. For the Kawi, this upgrade had to wait for 1981 and the GPz.
Why four-valves per cylinder? Valve breakages were common in early motorcycles, and as far back as the 1920s, combustion guru Harry Ricardo demonstrated how four smaller valves could provide better airflow, cooling, and combustion efficiency than two larger valves of equivalent area. This allowed for higher compression ratios while reducing thermal stress on the valves. By the 1970s, metallurgy had improved such that valve breakages were no longer a problem, and though four-valve heads and their associated valve trains are more complex, they’re now almost universally accepted for boosting performance and managing emissions.
Even without four valves, there was a host of other upgrades inside the MkII engine. Modifications to the crankshaft, cams, mufflers, and airbox, helped by 28mm (up from 26mm) pumper Mikunis, pushed output up 10bhp to 93bhp at 8,000rpm. At the same time, revisions to engine breathing, including a reed-valve controlled exhaust air induction system and TCB (transistor-controlled breakerless ignition) which, as it implies, did away with mechanical contact breakers.
Chassis changes were minor, though the frame was strengthened with double-wall tubing around the headstock. Notably, given the application of plastic bodywork on its three Japanese rivals, the MkII lacked any kind of fairing. That was reserved for the racier Z1-R. Instead, the MkII followed the corporate styling of squared off gas tank, triangular side panels and cast alloy wheels, and with an ever-so-slight step in the dual seat.
A couple of curiosities of the MkII that may cause some head scratching: although electric starters had been around for 70-odd years, Kawi put such little apparent faith in theirs that the MkII came fitted with an auxiliary kicker; and fitting a new final drive chain may cause some consternation, as the green guys chose the uncommon 630 size o-ring type. The only other bikes I’ve seen wearing one were the 1979 CB750F, one year only, and the Laverda 1200….
Cycle World concluded: “…the latest versions of the Z-l haven’t lost any ability — if anything. Kawasaki’s big Four is better in every respect… It’s relatively comfortable, rugged, and useful for anything a street bike should do — a fine all-around motorcycle. Kawasaki has changed the basic KZ thousand before, but never improved it as much with so few changes.” (Cycle World)
Elephant in the room: 1983 Honda CB1100F
“Better late than never,” wrote Cycle World in 1983, “Honda sets out to win the horsepower per dollar struggle.”
As with just about every contemporary motorcycle test, there’s a Honda in the mix, and it’s usually the benchmark. By 1980, an 1100cc motorcycle was the entry ticket to the Big Boys’ bike club, after Yamaha threw down the gauntlet in 1978 with the XS1100. Honda’s problem: they had no such machine on the books and were left behind while waiting for their new vee-fours. The DOHC CB900F, derived from the 1979-on CB750F, was a fine motorcycle but lacked the extra cubes that separated men from boys on the strip. Like the KZ1000 MkII, the CB1100F was a one-year-only model before being replaced by the new VF1000F vee-four in 1984.
The four-cylinder engine was relatively conventional for the time; air-cooled with chain-driven double overhead cams, four valves per cylinder, and five-speed transmission. The “square” cylinder dimensions (70 x 69mm, therefore a longer stroke than its competitors) manifested itself in a slightly lazier standing quarter but also provided more grunt for real world riding. Based largely on the CB900F, its bigger bro boasted another 20hp while adding around eight pounds to the plot.
Honda’s challenge was to control and manage the greater horsepower and (especially) torque from the new powerplant. Like its 900cc forebear, the CB1100F drivetrain was rubber-mounted in the frame to quell torsional vibration, and into the chassis went extra frame gusseting, a box-section swingarm running in needle roller bearings, and tubeless cast-alloy wheels in place of the earlier Comstars, which were made from aluminum extrusions and stampings joined with special fasteners. It also featured an air-assist fork with Honda’s TRAC system (Torque Reactive Anti-dive Control) managing the three-way adjustable front fork, while coil/damper units offered rear spring preload, compression, and rebound damping adjustment.
Unique features of the one-year CB1100F included a small fork-mounted sport fairing and instrument binnacle, a black chrome exhaust system with crossover, and a fuel tank blended into the side panels, as on earlier F models. At speed, the fairing would help to move some of the wind around the rider, but it provided minimal weather protection. Summing up, Classic Motorcycle Mechanics wrote that the CB1100F was, “A fine amalgam of an iron fist in a velvet glove.” MC
Bearings and bushings
Why did Suzuki and Kawasaki buck the trend to automotive-type one-piece cranks, plain bearings, and the necessary high-pressure oil feed?
A built-up crankshaft typically employs con rods forged in one piece, and these are generally stronger than the split-big-end con rods required for a one-piece crankshaft. The ball and roller bearings used on a built-up crank also have lower resistance losses than plain bearings. But the built-up crank comes at a price: the crank must be assembled with the big ends and rods in situ — a precision process requiring skilled workers, big presses and accurate alignment — not usually the stuff of mass-production. However, Suzuki and Kawasaki built an enviable reputation for extraordinarily strong and durable engines, particularly in the context of drag racing. Only the added cost of a built-up crank tipped the balance to a one-piece.
Perhaps equally revolutionary was the trend toward factory fairings — not your grandfather’s Windjammer, for all its other merits, but sleek, integrated bodywork that suggested speed. Honda neatly faired the gas tank into the side panels for the CB1100F; Yamaha committed fully with a frame-mounted fairing for the FJ1100; and Suzuki hired ex-BMW body man Hans Muth of Target Design to create the GSX1100 Katana fairing. And the green guys incorporated a handlebar fairing from the 1978 Z1-R.
