Cycle Magazine, January 1987

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Kawasaki Square Four 2 Stroke Prototype

Cycle Magazine, January

Sport bikes are shining for making corporate statements horsepower and handling, and manufacturers build reputations by cutting But the cost of high technology, now by the deflated dollar, has driven middleweights from $3500 to put 750s near the $5000 and sent the heavy artillery through the roof. Buyers are to turn blue in the thin-air of sport-bike price levels.

Now — the company that you Ninjas in arrest-me reds and blacks — has turned out the in pure and irreproachable white. The is also a genuine bargain, and easy to see why. In a world of four-cylinder sport-bikes, the EX takes its from a four-… vertical riding in a pipe-rack chassis no exotic frame alloys or suspension pieces, and only a front brake — for

With these credentials, the EX like low-volt amusement for certainly not a genuine sport

Until you look at the numbers. On the dyno, the EX pumped out an astonishing horsepower at 9500 rpm — both the Honda VF500 and the Yamaha FZ600. Only own 600 Ninja edges out the twin in power, but the EX has a power-to-weight ratio in the middleweight sport-bike class Topped with fuel, the EX 408.5 pounds, 34.5 less than the FZ600, under the Interceptor, nearly 60 shy of the 600

This power-to-weight advantage the EX in some less apparent Despite its single-disc front the EX500 stops from 60 mph in 115 making it the hardest-stopping middleweight on the There’s no denying the numbers, the is the real thing — a finger-in-the-socket middleweight rocket.

How did achieve such impressive at a price hundreds of dollars the other sporting middleweights? By the fundamentals. Consider the evolution of sport bikes.

Central to machines are four-…, four-cylinder — in both Vee and in-line As development and refinement continue to peak horsepower output, must strengthen chassis — brakes, suspension and — to support the extra The result is faster, better-handling yes, but also greater expense and weight.

Now the manufacturers that, having spent way up in horsepower, their only is to spend their way down in substituting aluminum for steel in handlebars, footpegs, etc. and steel components — brake discs — thin. Nevertheless, the biggest savings these days place at the very multi-cylindered of the new fours — in the powerplant. GSX-R1100 engine, for example, 52 pounds less than the unit it replaced, pounds don’t come cheap.

So technology, as well as economics, to be working to the advantage of sporting At one time, twins were so to multis that the fours horsepower more than any disadvantage from greater and weight.

Now, however, much of the high-technology first in four-cylinder engines to new sports (twin-cam, ultra-short … multi-valve lean burn, combustion chambers; sophisticated, ignitions) greatly diminishes the historical advantage — Today only a very and compact (read expensive) would hold a significant edge on an equally contemporary twin.

In the EX500, Kawasaki the high-tech/maximum-shrink four-cylinder formula by around the lighter, simpler, and compact parallel-twin borrowed the 454 LTD. It’s an elegant the EX500 can be as powerful as its four-cylinder yet significantly lighter without the use of chassis materials. For years, sport bikes have cut by using costly aluminum arms: the EX’s steel though patterned after the perimeter design, can afford to a swing arm made of steel.

The of the EX’s light engine far beyond the mere selection of First, there’s that stopping power from a front disc brake. suspension components, coping reduced cornering loads, can be further reducing weight, and cost.

And because the engine is — 10 inches across the block, 19 inches top to bottom and 15 wide at the crankcase — it can be fit in the chassis, close behind the wheel. As a side benefit, low and forward position allows a height — 30 inches lower than other sport bikes.

Significantly, the compact engine offer in aerodynamics as well. Slippery, bodywork helps four-cylinder bikes compensate for their and girth, but these streamlined cost a prince’s ransom.

low and narrow, the EX500 features a small upper fairing also offers an optional cowling for $92.42), yet our coastdown confirm the aerodynamics of the EX — the posted the lowest wind-drag in the middle weight class. piece of evidence, in top gear, the rider tucked behind the knees and elbows drawn the tank, the EX500’s tach hovers just above ten — 124 mph.

The EX500 follows a basic established in last year’s 250 the first of Kawasaki’s new-generation twins: Both bikes use four-valve, liquid cooled, parallel-twin engines with gearboxes, and high-revving crankshafts 14,000 rpm for the Ninja, 11,000 for the The 250’s engine was freshly while the EX draws many of its from the belt-drive 454 LTD crankcase, oil and water pumps, cylinder and valve train — rockers with screw-and-locknut

Converting the 454’s belt drive required more simply bolting on a new transfer and looping a length of #520 around a set of sprockets. The EX500 shares the cruiser bike’s ratios (both fifth and gears are overdrive), but the 454, its huge rear pulley, is quite low. Boosting top meant fitting a much rear sprocket, too small, in to prevent the chain from on the swing arm.

As a solution, combined taller primary-drive and final-drive sprockets, and the difference is Top speed in third is 82 mph for the 500, 64 for the in top gear, engine speed at 60 mph from the cruiser’s high rpm to 4935 for the EX sport bike.

the new Kawasaki taller helps vibration by reducing engine Vibration is controlled by two more methods, rubber engine and a gear-driven balancer shaft. The 500 has a crankshaft (the pistons and fall alternately) and therefore primary balance.

But because the cam drive requires the crankpins to be set apart, the EX’s engine produces a significant rocking which tries to pedal the ends around in circles the cases. The balancer, running at speed but in the opposite direction, out the rocking copple disturbance from the crankshaft. The balancer not, incidentally, deal the far less bothersome second (or secondary imbalance) that occurs in a 180-degree vertical

Despite Kawasaki’s efforts, the isn’t as smooth as either the 250 or the For practical reasons, counterbalancer can’t always be optimum and so vibration gets loose. the 500’s heavier (than the reciprocating parts may aggravate situation somewhat.

The 500 runs at low rpm, power pulses up through the seat and bars at smoothing to a pleasant rumble at 4500 rpm, then into one another as the tach swings toward redline. gearing shifts the vibration down the rpm scale, blurring the around town, tingling and feet at freeway speeds. At 60 mph the 454 may busier, but it runs smoother.

Still, at engine speeds 4000 rpm the EX is unruffled, much than either the Yamaha or the 600 Ninja.

With basic of 74 x 58mm — up from the 72.5 x 55mm figures the EX shares the same bore and as the ZX1000R Ninja. This is no the same economic forces forged Kawasaki’s decision to a twin determined the EX’s

Consider the advantages of identical and … numbers: Kawasaki that the pistons and connecting in the EX500 and 1000R are as similar as can be without bearing the same numbers. In fact, familiar abound in the EX500’s top end, and can save considerable tooling Shared technology from RD even more.

At every from drawing board to line, airbox to exhaust the EX500 bears the unmistakable of the 1000R.

For instance: The EX gets an 2.6 liters bigger than the about the same capacity as the Although the 500 uses the same semi-flat slide Keihin CVK as the 454, while the 1000R through 36mm Keihin, the EX500 and the 1000R tip their at a shallow 35-degree included and both use the same valve — 29mm inlet, exhaust. New cams increase the valve lift from 8.5 to closer to 1000R spec, and intake and exhaust valve from 270 degrees to 290 degrees identical to the 1000R.

The EX’s piston bumps the compression to 10.8:1 — a touch than the 454’s 10.7:1 and a away from the 1000R’s The 500 also has a higher redline the 1000, and therefore its piston at redline is higher than the highest, in fact, than any production motorcycle’s.

Given the it’s hardly surprising the EX and R engines share power From basement to redline, the power curve parallels the both engines making horsepower at 9500 rpm. for displacement, both engines come within half a of 103 BHP per liter, giving each the specific peak horsepower in its

The EX fares well against middleweights, its power curve roughly parallel to the FZ600’s and the 600 from 4000 rpm to 9500, a one-horsepower advantage over the FZ, behind the Ninja by the same Both the FZ and EX peak at 9500, the FZ 51.76 horsepower, the EX with the Ninja peaks 500 rpm later and six stronger. Honda’s VF500 lagging a full 10 horsepower the EX500 at 8000 rpm, to a peak of 51.07 at 12,000.

Despite its broad horsepower and power-to-weight advantage over the middleweights, the EX is not the fireball we expected. In mph roll-on tests, it trails the FZ in the top gears, outpulls the VF and the Ninja in runs … even the VF in fifth and sixth, but can’t the Ninja in the top two gears. Why? and carburation most likely the answer.

At low engine speeds, the mixers don’t respond as as the 600 Ninja’s smaller carbs, and the VF and FZ are geared significantly lower. The tall gearing also a price in quarter-mile acceleration; the FZ and Ninja are quicker and three to mph faster. The VF and EX, however, battle and weight advantages to a draw at the posting identical quarter-mile of 12.73 seconds at 102 mph.

of the numbers, the EX500 and Interceptor feel more different on the The VF500 engine is almost By contrast, the Kawasaki is alive parallel twin vibration. EX action is crisp and smooth, and its tall gearing, the 500 pulls around town and on the highway.

A pace doesn’t require a lot of at the shift lever, and at high the bike can be made to leap out of kicking hard enough at to lighten the front wheel in the gears.

In Cycle’s 1985 of sport bikes big and small, the emerged as the best sporting the most balanced piece. The chassis is four-cylinder contemporary: brakes, sophisticated suspension, fork, 16-inch front and short wheelbase to quicken Smaller, simpler and 50 pounds than the VF500, the EX constitutes an different approach, a combination of old and new still aimed at the VF’s balance of power and weight, and handling.

The Kawasaki’s square-section, frame weighs over 40 its suspension is decidedly low-tech, and the wears a rod-operated drum brake. Yet, like the 600 the chassis rolls on 16-inch front and rear, and the single-disc brake is so new only the EX and GPX get to use it. Coined the BAL Actuation Caliper), the new brake two live pistons on one side of the a method Honda has been for years.

Side by side, the two squeeze an elongated brake pad engages a band along the of the brake rotor. By engaging a but longer section of the rotor, the can be smaller in diameter and thus with no loss in swept compared to Kawasaki’s previous pad systems.

Furthermore, since the load of the bite on the disc is spread a wider area, the caliper has less tendency to flex, or like an opening clamshell hard breaking. The wall the pistons also adds to the caliper, allowing it to be made smaller, lighter. What BAL from Honda’s twin-piston is that Kawasaki uses of differing diameters.

The leading piston is smaller in diameter the trailing puck, which, claims, provides more wear and longer pad life. will tell. One thing’s with tire that let it the limits of braking traction, the stops with a vengeance.

the EX gets its steering quickness and control as a benefit of its light it can afford to stretch a bit between and here Kawasaki has given the its clearest advantage over the — roomy ergonomics. The EX more space in all directions a longer reach to the handlebar and seat-to-footpeg space allows six-footers to stretch out, a flatter set than other sport bikes provides to move about, and supple smoothes out the EX’s ride.

tall handlebars dictate a position more upright the FZ’s or the Ninja’s; some would have preferred a lower bar with a flatter angle and the footpegs moved an inch rearward. Still, in the middleweight class comes to the EX500’s ergonomic comfort and

The EX’s low-ball approach to however, gives the Interceptor an in ride quality. Though than the stiff-legged FZ and Ninja, the EX rival the suppleness of the VF’s sprung legs. With no for damping adjustment or air assist in the and only rear pre-load — through a spanner-type located at the top of the shock, and difficult to — the EX’s suspension lacks the operating range of the VF.

on the backroads the lightweight EX is easier on its than the heavier VF.

The EX500 to two distinct groups of riders rank novices and masters of country roads as well. and sure-footed no matter what the this new Kawasaki ranks the elite group of superior available in the U.S. — the FZ600 and the 20 Ninja — the backroad abilities of both.

Like the 250 Ninja, the EX is a demon in ess curves, flicking effortlessly side to side, its steering but always predictable. The FZ600 the tight stuff as well, but its low concentrate more weight on the arms. Like the Yamaha, the EX through fast sweepers unflappable stability, its Bridgestone tires providing excellent and enough tread to skim the feelers lightly across the

Spot-on spring and damping keep the Bridgestones planted in the stuff, but fast, rippled causes the front end to patter especially under hard Still, the feedback the EX gives at is marvelously direct and tractable.

the bargain price, Kawasaki skimped on amenities and Ninja for the EX. Standard features include bungee hooks, temperature fork lock/ignition, flush fuel cap, centerstand and halogen headlight nestled in a lined fairing.

Kawasaki’s presents a balance of handling and horsepower and simplicity that, of price, is almost unmatched in the class. The VF500 Interceptor that same wonderful and is till a smoother piece the EX. But the Kawasaki is much lighter, an edge in handling and sells for less.

On price alone, the EX is

The 1987 choice is clear: The has disappeared from Honda’s Which leaves riders the EX500 — fast, comfortable, trustworthy, and inexpensive. a recommendation like that, who freedom of choice?#9; —


Standing start ј sec. @

Acceleration, 0-60 sec.

Type#9;Four-…, parallel

#9;liquid-cooled with two chain-

overhead camshafts;

#9;four per cylinder

Bore and …#9;74.0 x

#9;(2.91 x 2.28 in.)

Displacement#9;498cc (19.6 cu. in.)


Carbuation#9;(2) 34mm constant-vacuum

Kawasaki Square Four 2 Stroke Prototype

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