Cycle Magazine, January 1987

Sport bikes are shining podiums for making corporate statements about horsepower and handling, and manufacturers donít build reputations by cutting corners. But the cost of high technology, now boosted by the deflated dollar, has driven Japanese middleweights from $3500 to $4000, put 750s near the $5000 mark and sent the heavy artillery punching through the roof. Buyers are beginning to turn blue in the thin-air stratosphere of sport-bike price levels.

Now Kawasaki -- the company that brought you Ninjas in arrest-me reds and air-raid blacks -- has turned out the EX500 in pure and irreproachable white. The EX500 is also a genuine bargain, and itís easy to see why. In a world of snarling four-cylinder sport-bikes, the EX takes its power from a four-stroke vertical twin riding in a pipe-rack chassis -- no exotic frame alloys or high-tech suspension pieces, and only a single-disc front brake -- for $2899. With these credentials, the EX seems like low-volt amusement for beginners, certainly not a genuine sport bike.

Until you look at the numbers. On the Kerker dyno, the EX pumped out an astonishing 51.76 horsepower at 9500 rpm -- rivaling both the Honda VF500 Interceptor and the Yamaha FZ600. Only Kawasakiís own 600 Ninja edges out the twin in peak power, but the EX has a power-to-weight ratio nothing in the middleweight sport-bike class approaches. Topped with fuel, the EX weighs 408.5 pounds, 34.5 pounds less than the FZ600, 50.5 under the Interceptor, nearly 60 shy of the 600 Ninja. This power-to-weight advantage benefits the EX in some less apparent ways. Despite its single-disc front brake, the EX500 stops from 60 mph in 115 feet, making it the hardest-stopping middleweight on the market. Thereís no denying the numbers, the EX500 is the real thing -- a serious finger-in-the-socket middleweight rocket.

How did Kawasaki achieve such impressive performance at a price hundreds of dollars below the other sporting middleweights? By rethinking the fundamentals. Consider the evolution of Japanese sport bikes. Central to these machines are four-stroke, four-cylinder engines -- in both Vee and in-line configurations. As development and refinement continue to boost peak horsepower output, designers must strengthen chassis components -- brakes, suspension and frames -- to support the extra power. The result is faster, better-handling machines, yes, but also greater complexity, expense and weight.

Now the manufacturers find that, having spent their way up in horsepower, their only course is to spend their way down in weight, substituting aluminum for steel in frames, handlebars, footpegs, etc., and shaving steel components -- like brake discs -- wafer thin. Nevertheless, the biggest weight savings these days takes place at the very multi-cylindered heart of the new fours -- in the powerplant. Suzukiís GSX-R1100 engine, for example, weighs 52 pounds less than the four-cylinder unit it replaced, pounds that donít come cheap.

So technology, as well as economics, seems to be working to the advantage of sporting twins. At one time, twins were so inferior to multis that the fours increased horsepower more than offset any disadvantage from greater complexity and weight. Now, however, applying much of the high-technology first seen in four-cylinder engines to new sports twins (twin-cam, ultra-short stroke designs, multi-valve lean burn, high-compression combustion chambers; sophisticated, high-output ignitions) greatly diminishes the multisí historical advantage -- horsepower. Today only a very light and compact (read expensive) multi would hold a significant power edge on an equally contemporary sporting twin.

In the EX500, Kawasaki avoided the high-tech/maximum-shrink four-cylinder formula by building around the lighter, simpler, and more compact parallel-twin borrowed from the 454 LTD. Itís an elegant solution, the EX500 can be as powerful as its four-cylinder counterparts, yet significantly lighter without the use of expensive chassis materials. For years, four-cylinder sport bikes have cut weight by using costly aluminum swing arms: the EXís steel frame, though patterned after the latest perimeter design, can afford to carry a swing arm made of steel.

The effects of the EXís light engine reach far beyond the mere selection of materials. First, thereís that amazing stopping power from a single front disc brake. Next, suspension components, coping with reduced cornering loads, can be simplified, further reducing weight, complexity and cost. And because the engine is compact -- 10 inches across the cylinder block, 19 inches top to bottom and 15 inches wide at the crankcase -- it can be fit forward in the chassis, close behind the front wheel. As a side benefit, this low and forward position allows a seat height -- 30 inches -- lower than other middle-weight sport bikes.

Significantly, the EXís compact engine offer advantages in aerodynamics as well. Slippery, full-coverage bodywork helps four-cylinder sport bikes compensate for their weight and girth, but these streamlined panels cost a princeís ransom. Light, low and narrow, the EX500 features only a small upper fairing (Kawasaki also offers an optional lower cowling for $92.42), yet our coastdown tests confirm the aerodynamics of the EX -- the twin posted the lowest wind-drag figure in the middle weight class. Another piece of evidence, in top gear, with the rider tucked behind the windscreen, knees and elbows drawn against the tank, the EX500ís tach needle hovers just above ten grand -- 124 mph.

The EX500 follows a basic formula established in last yearís 250 Ninja, the first of Kawasakiís new-generation sporting twins: Both bikes use DOHC, four-valve, liquid cooled, counterbalanced parallel-twin engines with six-speed gearboxes, and high-revving crankshafts -- 14,000 rpm for the Ninja, 11,000 for the EX500. The 250ís engine was freshly minted, while the EX draws many of its components from the belt-drive 454 LTD crankcase, clutch, oil and water pumps, cylinder head and valve train -- forked rockers with screw-and-locknut adjusters.

Converting the 454ís belt final drive required more than simply bolting on a new transfer case and looping a length of #520 chain around a set of sprockets. The EX500 also shares the cruiser bikeís transmission ratios (both fifth and sixth gears are overdrive), but the 454, with its huge rear pulley, is geared quite low. Boosting top speed meant fitting a much smaller-diameter rear sprocket, too small, in fact, to prevent the chain from dragging on the swing arm. As a solution, Kawasaki combined taller primary-drive gears and final-drive sprockets, and the difference is significant. Top speed in third is 82 mph for the 500, 64 for the 454; in top gear, engine speed at 60 mph drops from the cruiserís high 5740 rpm to 4935 for the EX sport bike.

Gearing the new Kawasaki taller helps minimize vibration by reducing engine speed. Vibration is controlled by two more direct methods, rubber engine mounts and a gear-driven balancer shaft. The 500 has a 180-degree crankshaft (the pistons rise and fall alternately) and therefore perfect primary balance. But because the central cam drive requires the crankpins to be widely set apart, the EXís engine also produces a significant rocking couple which tries to pedal the crank ends around in circles inside the cases. The balancer, running at crank speed but in the opposite direction, cancels out the rocking copple disturbance emanating from the crankshaft. The balancer does not, incidentally, deal with the far less bothersome second harmonic (or secondary imbalance) that naturally occurs in a 180-degree vertical twin.

Despite Kawasakiís efforts, the EX500 isnít as smooth as either the 250 or the 454. For practical reasons, counterbalancer placement canít always be optimum and so some vibration gets loose. Further, the 500ís heavier (than the 454ís) reciprocating parts may aggravate this situation somewhat. The 500 runs roughest at low rpm, power pulses welling up through the seat and bars at idle, smoothing to a pleasant rumble at about 4500 rpm, then melting into one another as the tach needle swings toward redline. Tall gearing shifts the vibration band down the rpm scale, blurring the mirrors around town, tingling hands and feet at freeway speeds. At 60 mph the 454 may sound busier, but it runs smoother. Still, at engine speeds above 4000 rpm the EX is unruffled, much smoother than either the Yamaha FZ600 or the 600 Ninja.

With basic dimensions of 74 x 58mm -- up from the 454ís 72.5 x 55mm figures -- the EX shares the same bore and stroke as the ZX1000R Ninja. This is no coincidence: the same economic forces that forged Kawasakiís decision to build a twin determined the EXís displacement.

Consider the advantages of identical bore and stroke numbers: Kawasaki reports that the pistons and connecting rods in the EX500 and 1000R are as similar as components can be without bearing the same part numbers. In fact, familiar pieces abound in the EX500ís top end, and thus can save considerable tooling costs. Shared technology from R&D saves even more. At every step, from drawing board to assembly line, airbox to exhaust port, the EX500 bears the unmistakable stamp of the 1000R.

For instance: The EX gets an airbox 2.6 liters bigger than the 454ís, about the same capacity as the 1000Rís. Although the 500 uses the same 34mm semi-flat slide Keihin CVK carbs as the 454, while the 1000R breathes through 36mm Keihin, both the EX500 and the 1000R tip their valves at a shallow 35-degree included angle and both use the same valve size -- 29mm inlet, 24.7mm exhaust. New cams increase the EXís valve lift from 8.5 to 8.7mm, closer to 1000R spec, and bump intake and exhaust valve duration from 270 degrees to 290 degrees -- identical to the 1000R.

The EXís flat-topped piston bumps the compression ratio to 10.8:1 -- a touch more than the 454ís 10.7:1 and a jump away from the 1000Rís 10.2:1. The 500 also has a higher redline than the 1000, and therefore its piston speed at redline is higher than the 1000Rís, highest, in fact, than any other production motorcycleís.

Given the similarities, itís hardly surprising that the EX and R engines share power characteristics. From basement to redline, the 500ís power curve parallels the 1000ís, both engines making peak horsepower at 9500 rpm. Corrected for displacement, both engines also come within half a horse of 103 BHP per liter, giving each the highest specific peak horsepower in its class.

The EX fares well against other middleweights, its power curve running roughly parallel to the FZ600ís and the 600 Ninjaís from 4000 rpm to 9500, holding a one-horsepower advantage over the FZ, falling behind the Ninja by the same amount. Both the FZ and EX peak at 9500, the FZ with 51.76 horsepower, the EX with 51.72; the Ninja peaks 500 rpm later and six horsepower stronger. Hondaís VF500 Interceptor, lagging a full 10 horsepower behind the EX500 at 8000 rpm, pulls to a peak of 51.07 at 12,000.

Despite its broad horsepower curve and power-to-weight advantage over the other middleweights, the EX is not the fireball we expected. In 45-70 mph roll-on tests, it trails the FZ in the top three gears, outpulls the VF and the Ninja in fourth, runs dead even with the VF in fifth and sixth, but canít match the Ninja in the top two gears. Why? Gearing and carburation most likely hold the answer. At low engine speeds, the EXís mixers donít respond as crisply as the 600 Ninjaís smaller carbs, and both the VF and FZ are geared significantly lower. The EXís tall gearing also exacts a price in quarter-mile acceleration; both the FZ and Ninja are quicker and three to four mph faster. The VF and EX, however, battle gearing and weight advantages to a draw at the strip, posting identical quarter-mile runs of 12.73 seconds at 102 mph.

Regardless of the numbers, the EX500 and Interceptor couldnít feel more different on the street. The VF500 engine is almost appliance-smooth. By contrast, the Kawasaki is alive with parallel twin vibration. EX clutch/gearbox action is crisp and smooth, and despite its tall gearing, the 500 pulls well around town and on the highway. A fast pace doesnít require a lot of work at the shift lever, and at high revs the bike can be made to leap out of turns, kicking hard enough at 7500 to lighten the front wheel in the lower gears.

In Cycleís 1985 comparison of sport bikes big and small, the VF500 emerged as the best sporting package, the most balanced piece. The VF500ís chassis is four-cylinder contemporary: triple-disc brakes, sophisticated suspension, anti-dive fork, 16-inch front wheel and short wheelbase to quicken steering. Smaller, simpler and 50 pounds lighter than the VF500, the EX constitutes an entirely different approach, a combination of old and new technology, still aimed at the VFís magical balance of power and weight, horsepower and handling.

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

Side by side, the two pistons squeeze an elongated brake pad which engages a band along the perimeter of the brake rotor. By engaging a narrower but longer section of the rotor, the disc can be smaller in diameter and thus lighter with no loss in swept area compared to Kawasakiís previous single-piston/round pad systems. Furthermore, since the load of the caliperís bite on the disc is spread over a wider area, the caliper itself has less tendency to flex, or spread like an opening clamshell under hard breaking. The wall between the pistons also adds strength to the caliper, allowing it to be made thinner, smaller, lighter. What differentiates BAL from Hondaís twin-piston system is that Kawasaki uses pistons of differing diameters. The leading (rearmost) piston is smaller in diameter than the trailing puck, which, Kawasaki claims, provides more even wear and longer pad life. Time will tell. One thingís apparent, with tire that let it explore the limits of braking traction, the EX500 stops with a vengeance.

Because the EX gets its steering quickness and chassis control as a benefit of its light weight, it can afford to stretch a bit between axles, and here Kawasaki has given the EX500 its clearest advantage over the Interceptor -- roomy ergonomics. The EX offers more space in all directions -- a longer reach to the handlebar and more seat-to-footpeg space allows even six-footers to stretch out, a wider, flatter set than other middleweight sport bikes provides room to move about, and supple padding smoothes out the EXís ride. Fairly tall handlebars dictate a seating position more upright than the FZís or the Ninjaís; some testers would have preferred a slightly lower bar with a flatter grip angle and the footpegs moved about an inch rearward. Still, nothing in the middleweight class comes close to the EX500ís ergonomic comfort and versatility.

The EXís low-ball approach to suspension, however, gives the Interceptor an advantage in ride quality. Though smoother than the stiff-legged FZ and Ninja, the EX canít rival the suppleness of the VFís softly sprung legs. With no provisions for damping adjustment or air assist in the fork, and only rear pre-load adjustment -- through a spanner-type collar located at the top of the shock, and difficult to reach -- the EXís suspension also lacks the operating range of the VF. Still, on the backroads the lightweight EX is easier on its suspension than the heavier VF.

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

Like the 250 Ninja, the EX is a demon in light ess curves, flicking effortlessly from side to side, its steering light but always predictable. The FZ600 handles the tight stuff as well, but its low handlebars concentrate more weight on the riderís arms. Like the Yamaha, the EX bores through fast sweepers with unflappable stability, its Bridgestone Excedra tires providing excellent grip and enough tread to skim the footpeg feelers lightly across the asphalt. Spot-on spring and damping rates keep the Bridgestones planted in the rough stuff, but fast, rippled pavement causes the front end to patter slightly, especially under hard braking. Still, the feedback the EX gives at speed is marvelously direct and tractable.

Despite the bargain price, Kawasaki hasnít skimped on amenities and Ninja goodies for the EX. Standard features include fold-out bungee hooks, temperature gauge, fork lock/ignition, flush mount fuel cap, centerstand and quartz halogen headlight nestled in a fully lined fairing.

Kawasakiís EX500 presents a balance of handling and comfort, horsepower and simplicity that, regardless of price, is almost unmatched in the sport-bike class. The VF500 Interceptor strikes that same wonderful balance, and is till a smoother piece than the EX. But the Kawasaki is much lighter, holds an edge in handling and sells for hundreds less. On price alone, the EX is peerless.

The 1987 choice is clear: The VF500 has disappeared from Hondaís lineup. Which leaves riders with the EX500 -- fast, precise, comfortable, trustworthy, and inexpensive. With a recommendation like that, who needs freedom of choice? O

 

TEST SPECIFICATIONS

Make and Model Kawasaki EX500

Price, suggested retail (as of 10/1/86) $2899

Performance

Standing start ľ mile 12.73 sec. @

102.21 mph

Acceleration, 0-60 mph 3.76 sec.

45-70 mph, top gears (4) 4.08 sec., 343 ft.

(5) 5.92 sec., 492 ft.

(6) 6.62 sec., 589 ft.

Braking, 60-0 mph 115 ft.

Horsepower @ 60 mph 9.58

Engine rpm @ 60 mph, top gear 4935

Average fuel consumption rate 48 mpg

(20.4 km/l)

Cruising range (main/reserve) 202/29 mi

(237/46 km)

Load capacity

(GVWR less curb weight 418.5 lbs (189.8 kg)

Maximum speed in gears

@ engine redline (1) 44 (2) 63

(3) 82 (4) 101 (5) 118 (6) 133

Engine

Type Four-stroke, parallel twin;

liquid-cooled with two chain-

driven overhead camshafts;

four valves per cylinder

Bore and stroke 74.0 x 58.0mm

(2.91 x 2.28 in.)

Piston Displacement 498cc (19.6 cu. in.)

Compression ratio 10.8:1

Carbuation (2) 34mm Keihin constant-vacuum

Exhaust system Two-into-two

Ignition Batter-powered, inductive

magnetically triggered

Air filtration Foam element

Oil filtration Paper element, disposeable

Oil Capacity 3.6 qts. (3.4l)

Bhp @ rpm 51.72 @ 9500

Torque @ rpm 30.86 @ 8000

Transmission

Type Six-speed, constant mesh,

wet-clutch

Primary drive Straight cut gear:

23/61, 2.662

Final drive #520 Chain;

42/16 sprockets, 2.625

Gear ratios (transmission) (1) 36/14, 2.571

(2) 32/18, 1.78 (3) 29/21, 1.38

(4) 27/24, 1.12 (5) 25/26, 0.96

(6) 23/27, 0.85

Gear ratios (overall) (1) 17.87 (2) 12.37

(3) 9.60 (4) 7.83

(5) 6.88 (6) 5.92

 

Chassis

Type Double -downtube, full-cradle

perimeter frame: box section

stee swing arm

Suspension, front Center-axle fork with

36mm tubes and 5.5 in.

(140mm) of travel

rear (1) Shock absorber, adjustable

for spring preload, producing 3.9 in.

100mm) of rear-wheel travel.

 

Wheelbase 56.6

Rake/trail 27.5į/3.5 in. (89mm)

Brake, front Hydrolic, single-disc with

Dual-piston caliper

rear Rod-actuated, single-

leading shoe drum

Wheel, front Cast, 2.15 x 16

rear Cast, 2.5 x 16

Tire front 100/90-16 54H

Bridgestone Excedra G533

rear 120/90-16 83H

Bridgestone Excedra

Seat height 30.3 in (770mm)

Ground clearance 4.9 in (124mm)

Fuel capacity (main/reserve) 4.2 (0.6) gals.

(15.9/2.2l)

Curb weight (full tank) 408.5 lbs (185 kg)

Test weight 558.5 lbs (253 kg)

 

Electrical

Power source AC Alternator

Charge control Solid-state voltage regulator

Headlight beams (high/low) 60/55 watts

Tail/stoplights 8/27 watts

Battery 12V 14AH

 

Instruments

Includes Speedometer, odometer, tripmeter

tachometer with 11,000 rpm redline

water temperature gauge, indicators

for oil pressure, high-beam, headlight on,

turn signals, neutral

 

Speedometer error

30mph indicated, actual 29.50

60 mph indicated, actual 57.53

 

Customer Service Contact

Kawasaki Motors Corporation

P.O. Box 25252

Santa Ana, CA 92799-5252

(714) 770-0400

 

 

 

 

 

 

 

 

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