Cycle Magazine, 1973
The Ducati 750, the Honda 750, the Sportster 1000,
the Kawasaki 903, the triumph Trident 750,
the Norton Commando 750, and the Kawasaki 750
were called together for Cycle’s second
Superbike Comparison Test. It was the
fastest field of stockers in history.
Total evaluation time: more than six weeks.
Total number of winners: one.
JESS THOMAS, DALE BOLLER AND COOK NEILSON
• Cycle’s March, 1970 issue contained the first head-to-head comparison test ever published; the bikes under evaluation were called Superbikes, embodying those elusive character traits which allowed optimum braking, acceleration, and cornering. That was all we measured, since at the time it seemed reasonable that the buyer oriented in a purely performance (or performance image) direction would be willing to overlook the absence of frills and window-dressing. We called the test “The Big Seven”—the number of motorcycles that we felt legitimately filled the bill.
In the ensuing two years, enough change has evolved in the Superbike ranks to justify another look at the field. Of the original participants, only the Norton, the Honda, the Trident and the Sportster remain. The BSA 750 will not be offered for 1973, the Suzuki 500 shouldn’t have been included to start with, and the Kawasaki 500, somewhat de-fanged and better mannered, has been shouldered aside by its high-intensity big brother, the Mach IV 750. Filling the vacant slots are the new-dimension Ducati 750 and the frontier-stretching Kawasaki 903cc Z1.
The letters went out to the entrants:
Each participant may supply, and have on hand during the period of the test, as many mechanics as he would like. The mechanics may work on the bikes at anytime during the test; they may not bring the bikes home to work on them overnight, and they may not remove them from the area of the test unless to correct a major deficiency.
And now to the specifics:
1) Each motorcycle must be stock and standard, with the following exceptions:
A) Final-drive gearing is optional, as long as the sprockets are available from your Friendly Local Dealer;
B) Road-racing tires may be fitted for the high-speed handling segment—but stock wheels must be used. If any of you foresee a ground-clearance problem, we recommend you stay with stock tires;
C) Any rear tire may be used for acceleration testing. If any of you feel you might benefit from a drag-slick, we recommend either an Avon or an M&H #321.
2) We expect each motorcycle to have been the beneficiary of a careful break-in and a super-tune. By super-tune we mean making the motorcycle run as well as possible using selective assembly of standard components. Valve jobs are permitted for the four-strokes, although modifications to port shape, size, or finish will be construed as illegal; and blue-printing of the two-stroke’s port timing will also be permitted.
3) All exhaust systems must be absolutely stock for the year and model tested—no 1971 exhaust systems on 1972 or 1973 motor-cycles.
4) Brake friction material must be stock, and so must the brakes.
5) And if you get caught cheating, the world will know!
The ground rules were set. In an effort to keep things relevant and consistent the battleground once again was Orange County International Raceway, just south of Los Angeles. Performance figures are greatly affected by road surface properties and it was felt by all concerned that a more stable perspective would result from holding the test at the same site which Cycle Magazine used two years earlier.
Our staff met the participants at OCIR on the morning of August 28. There were only seven motorcycles in the test—but there must have been double that number of vans lined up at the gate, their occupants waiting to check our methodology, waiting to see . . . who was going to win.
And there was going to be a winner. Our first Superbike Comparison Test had gathered the seven strongest motorcycles available for sale in the world and had evaluated them side by side. The results were published—acceleration, braking distance, and lap-times—but no conclusion was reached. This test would be different. We would over the course of the three-day test period try to establish just exactly which Superbike offered the most absolute performance, and where the others stacked up relative to it. A scoring system: the bike that, for example, delivers the quickest quarter mile elapsed time would receive 100 points. The rest would receive points based on the percent-age of the winner’s time that they were able to produce. There would be four points-awarding categories: lap time, acceleration time, acceleration speed and braking force. The results do not reflect the best motorcycle, nor do they reflect our own preference. They merely reflect proficiency in the four Superbike categories, irrespective of creature comforts, irrespective of gas mileage, irrespective of component quality, irrespective of physical appearance and vibration control and brake-squeal and clutch operation and all other considerations which together help the perspective buyer decide which motor-cycle is the best for him.
As such the Superbike Comparison Test is limited but it’s pure, and the numbers that count towards the final point total are just as absolute as we, or any other group of testers, can make them.
A quick look at the participating motor-cycles: the Sportster has changed more between 1972 and 1973 than it has between any other two model years. For one thing you Sportster owners are going to have to expunge for your vocabulary one of your favorite phrases: Cheap Japanese Junk. The 1973 Sportster has new forks this year made (guess where?) in Japan. And so are the mufflers. Between the highly improved front forks glistens a new Kelsey-Hayes hydraulic disc brake. The XLCH also has benefited from a new steering head casting, matte-black crankcases, and red, white, and blue laser stripes disposed in a semi-sunburst pat-tern on the black fuel tank. As we were to find out shortly the mufflers, while admirably efficient in their noise-control capacity, are punishingly restrictive. Still, the bike retains those qualities that have made it one of the world’s most popular motorcycles since its introduction in 1957: It’s big, demanding and masculine, and it projects the image of a bruiser. But everybody knows by now that the Sportster’s crackling performance image is at variance with its own performance figures. Nobody who buys it gives a damn.
The Honda CB750 is as restrained and as mature as the Sportster is blustery; it’s un-matched for sophistication and thoughtful development. Like the startling Kawasaki 903 the Honda is a broad-spectrum motor-cycle whose appeal spreads in all directions, a motorcycle capable of doing anything and everything consistent with the pleasurable transportation of a human being down a stretch of paved road. Like the 903 the Honda is harshly restricted by the parameters of a test like this one; while it can do every-thing necessary to give a good account of itself, it can do so much more.
The Ducati GT750 is identical to the one tested in Cycle’s October 1972 issue, a highly modified version of which won the International Formula 750 race at Imola last April. The true essence of the Duke was captured by the men who developed it; they called the motorcycle “Long-legs” after savoring its silky-smooth, easy loping, torquey, graceful manner. Other motorcycles can perform individual feats better than the Ducati; few can do it all as brilliantly and even fewer match it for balance. None matches it for exhaust noise.
Kawasaki was represented by two motor-cycles, a situation that caused some discomfort in the ranks of the loyal opposition until it was pointed out that this was a Superbike test, and to exclude either the Mach IV or the Z1 would be ridiculous and unfair (a postulate borne out by the ultimate results). The bikes are as different as night and day. The Mach IV is the quickest, most intense; most single-purpose street machine ever built for general consumption, a streaming, purple-eyed monster that does everything with a shriek and whose only God is performance. Lay at its feet the hottest production vehicle you can name—two wheeled or four—and the Mach IV will chuckle, snort, and eat it alive. Its limitations are exactly as you would suspect: the engine makes a lot of racket, it doesn’t have much of a reputation for gas economy, and you have to know what you are doing to live with it in comfort. For 1973, the 750’s carburetion system has been recalibrated for more sensible gas mile-age, more accurate throttle response and slightly smoother running.
The zingy Z1, the same motorcycle we tested in the November issue, offers performance a whisker away from that of the Mach IV with none of its sibling’s draw-backs. It’s quiet, pleasant, easy to deal with, consistent, and terribly fast. As we said in the November test, the Z1 is the first of a new generation of bikes. Its appeal is even wider than the Honda’s, and while the Mach IV is the ultimate performer, the Z1 is the ultimate motorcycle, close to being all things to all people. We were amazed when we first tested it we were soon to find out that the depth of the 903’s talent was more far-reaching than anyone, including the representatives of Kawasaki, had suspected.
The British contingent offered few surprises. The Norton Commando Roadster was identical to the Interstate we tested in the May, 1972 issue—except for the capacity of the fuel tank. The Triumph Trident, generally recognized as the best-looking bike in the test, had followed a predictable table of development: for 1973 the howling three-cylinder, with a new paint-job and a polished rear hub assembly, draws still closer to the traditional and classic Limey look of the Bonneville, and it has been blessed with a new Lockheed disc brake up front. It’s only cursory flaw is handlebar style: ape hangers went out five years ago and the British haven’t quite gotten the message.
With the bikes came the mechanics. Some had worked with us before—and some were new. Jim Swartzlander, quiet, competent, realistic and thorough, mother-henned the Honda; Jack Murphy, the man behind the drag-racing success of Tony Nicosia, had the Kawasaki 750 so well prepared that he scarcely looked at it for the duration of the test; resourceful Bob Ellison, who had worked with us on the original Superbike Comparison Test and who knew the rules better than we did, attended the Trident; Brian Slark and Bob Yacenda thrashed on the Norton; laconic Jim Wismer from Harley-Davidson of Westminster checked over the Milwaukee-fettled Sportster; A.J. Lewis, chief mechanic in Bob Blair’s ZDS distributorship, tuned the Ducati; and Jeff Shetler had been assigned to the Kawasaki Z1.
Since the new Westlake Village Cycle shop has been established, no preliminary measurements were necessary—all bikes would be disassembled and checked for legality at the conclusion of the test. A few mechanics fiddled with tire pressure; a meeting was held, explaining the procedures and the timetable; and it was time to begin.
Our first performance test was to measure stopping ability for each Superbike. Two years ago we ran the bikes through the drag strip clocks at an indicated 60 mph to get the true speed. Then each machine was rid-den toward a pair of pylons at an indicated 60 mph. The object was to begin hard braking right on the pylon line. Each bike required a slightly different method and lead time at the braking point. The method was fairly accurate in determining maximum braking effort, but was biased against bikes with higher true speeds and did not make a statement about the mechanical lag in each machine’s braking system.
This year, we changed the method. Each bike was ridden through the electronic timer until a true 60 was reached, then a corresponding line was drawn on the speedometer face with a marking pen. But that was only an indicator for the rider: we placed the braking point pylons just beyond the final mph photo-electric cell so that the true speed of each bike was monitored for each panic stop test.
To get an accurate indicator of where each bike’s brakes were applied each time, an electrically-actuated dye marking gun was fitted to a rear shock absorber. The brake light switch was disconnected from its light and wired to the gun. Brakes go on, gun goes off. On each test, the speed was recorded from the timer, and the distance from the dye mark on the pavement to the gun on the stopped motorcycle was measured carefully.
After the last comparison test, we raved on and on and on about the Honda’s disc brake. And then we bitched and moaned something shocking about the drum brakes on the other bikes. Apparently we had some effect: All the competitors in the test were equipped with disc front brakes. There was a marked difference in the ratio of hand lever pressure to braking force between the bikes, but they were all good: damned good.
To compensate for the small differences in trap speed, we converted all of the distance and speed figures into acceleration, in terms of feet-per-second per second. Mathematically, this is expressed as:
½ (speed) ²
Here, the speed is changed from miles-per-hour and expressed in terms of feet-per-second. Then to express the force in more familiar terms, the acceleration figure is divided by the acceleration caused by the earth’s gravitational field on a free falling object at sea level. This gives the braking force in terms of Gs.
The speed of the Ducati in the trap was 61.01 mph. This was equivalent to 89.48ft./ sec. Its stopping distance was 137.833 ft. Plugging these figures into the acceleration formula gives:
Acceleration = = 29.04 ft/sec²
Dividing 29.04 ft./sec.² by 32.2 ft./sec.² gives 0.902 G. This force was the fourth best we measured. The Ducati stopped smoothly and straight as a die every time. Front tire friction against the pavement was the limiting factor in the Duke’s stopping. The tire would moan and stay on the verge of locking for the whole distance.
The Harley-Davidson’s best combination of trap speed and stopping distance was 60.32 mph and 145.25 ft. A respectable figure, but only good enough to generate .837 G and last place in the battle of the stoppers. The Sportster’s 10-inch disc and the Kelsey-Hayes caliper combination was the only one that could not be brought to the verge of wheel lock. Expert riders may want to re-place the standard Sportster caliper pads with ones having a higher coefficient of friction to get faster stops.
The illustrious Honda Four, outright winner of the braking test three years ago, could manage only .896 G this time, and was relegated to fifth place. Again, tire bite kept the Honda from better stops. The fantastic stop during the previous test was accomplished while using a Goodyear roadracing tire. It was almost impossible to slide that tire, but the standard Bridgestone rib on the Honda could be kept from squirming with moderate hand pressure.
Kawasaki’s 750cc triple didn’t feel as if it were pulling down vitally at all. In fact, the front wheel started hopping slightly during the latter stages of each stop, a trick which required reducing the brake lever pressure somewhat. It was a deceptive feeling: the machine hopped to a complete halt in 128.417 feet from a true speed of 59.52 mph. That gave it a rating of .922 G, the absolute best of the lot. The Dunlop F6 front tire gave great grip, moaning and howling the whole way.
The big, massive-feeling 903 Kawasaki gave a more accurate feel of its intensions. From a true 59.01 mph, it dove and tire-howled to a stop in 126.417 ft. It was a jet-smooth and gut-tightening feeling, a lot like a downward trip in a quick elevator. We suspect that the lower center of gravity in the 903 was the chief factor in the difference in feeling. The .920 G generated by the big Kawasaki was good for second place to its smaller brother.
The Norton was smooth and predictable. Its Avon 4.10 x 19 tire was its limiting factor. The wheel could be predictably locked at will, and kept at what seemed like a pre-mature howl for the whole distance. From a speed of 60.16 mph, the Roadster anchored down in 131.958 feet to generate our third-ranking .916 G force. We had a problem with Triumph’s Trident. It was the only bike that didn’t have a hydraulic stop light switch on the front brake. It was an early pilot-production model, rushed from England for our test. The switches didn’t come in time. After a lot of fiddling and adjusting, the rod-actuated rear brake switch was wired to our indicator gun and adjusted to fire at the appropriate coincidental time with front wheel brake application. A fussless stop in 142.875 feet from a true 61.64 mph gave the 750 triple sixth spot with a G-force of .889.
In a surprising display of fairness, all of the competitors in the test chose to keep their standard front tires mounted through-out the test. What our test bikes did could be repeated on a clean road by any carefully-tuned production counterpart.
With the nerve-wracking panic stops completed (they took a day and a half to do), we moved to the road circuit.
Being able to run a fast bike to its limit on a closed circuit is an enlightening, rare, re-leasing experience. No oil, rocks, dogs, cars, cops or paperboys to worry about around the next bend in the road. Just you and the machine. After the course is learned roughly (you know which direction the next turn takes), your choice of path gets narrower each lap as you learn where you have to be in order to not have to ease the throttle or get on the brakes. If the suspension springs have rates high enough and their movement is correctly controlled by shock absorbers and there are good tires on the bike, you will soon find the cornering limit. Foot rests, mufflers, or stands are usually the first things to touch down.
Then there’s that sharp turn up ahead: how far can you stuff the bike before you absolutely have to get the brakes on? How much do you have to get slowed down, how much precious speed do you have to give up, which gear should you be in to get maxi-mum acceleration exiting the turn? If you have time to think, you’re going too slow. After a while, a few laps or a few years, it all starts to blend. Your total consciousness is absorbed every second. The whole thing becomes a rhythm that is automatic and repeatably reliable.
Fancy yourself at a circuit with seven of the fastest, best stopping, most accurately sprung, precision-tuned road-burners in the whole world. A vastly experienced professional tuner stands by each machine, ready to warm up the engine when you’re good and ready to brutalize his pride and joy. That’s the position we found ourselves in at Orange County International’s road circuit that fine day.
First up was the Honda. From the onset it was apparent that the “softening-up” was going to slow it down on the road course. In an effort to make the 750 Four more suitable to its biggest market, Honda’s engineers have raised the overall gear ratio, fitted softer clutch springs, installed quieter and more restrictive mufflers, and made an internal engine modification that we’ll tell you about in the inspection part of the test. The bike is simply slower than it was.
With its gears being shifted at 8000 rpm the Four fairly purred around the track. Even with the shock absorber springs adjusted to their highest preload position the center stand would ground pretty early on the Honda. The only suspension problem en-countered was vicious rear wheel-hop during hard braking and down-shifting. A floating rear brake plate would probably cure the problem. If rear brake usage was eased off and the downshifting left until a slightly lower rpm was reached, the hopping ceased. Obviously a lot of time was lost in the bar-gain. Other than these comments, the Honda performed faultlessly, if half-heartedly, while being crowded as hard as it would go. With a best lap time of 47.0 sec. The bike was 2.1 sec. Slower than during the 1970 test, for a sixth place finish.
Since the controls are exactly the same as those on the Honda, we ran the Z1 Kawasaki next. The machine feels bigger than it is. After a few laps at incredible speeds, the rear shocks got hot and failed to damp the swingarm movement properly and the bike began to wallow radically in the fast turns. The rear brake followed suit and became useless after it got good and hot. Our rider suffered quite a bit of hassle with the shift lever. While the action of the shifting mechanism was perfect, the footrest was too close to the generator bulge in the engine case and the boot toe continually hit the case. And when the oil leak from the generator saturated the lever, causing its rubber cover to slide off, things got a little slippery after a few laps. The steering was very nimble and deliberate and the front brake functioned perfectly for the whole session. You can lean the Z1 way over before the pegs and stands begin to drag. With better rear shocks and a disc rear brake, the 903cc mind-stopper would circulate incredibly quickly, even on our tight test course. As it was the Z1 tied for the fastest lap with a time of 44.5 sec.
Kawasaki’s three cylinder, two-stroke Mach IV felt entirely different. For one thing, it sounded awful. But rattling, wheezing, pinging, knocking, and vibrating, the bike went like a rocket ship. Engine feel was deceptive, as it was only turning 7000 rpm at max power, and you just don’t realize the acceleration is as great as it is. Shock absorber failure begets a lot of wallowing on the Mach IV after a few quick rounds, just like the other Kawasaki, but both brakes held up to perfection for the whole 10-lap session. The muffler grounded fairly early on the right side and severely limited cornering angle. And when the pipe drags the rear wheel lifts off the pavement, causing the bike to do a huge whing-ding wobble. Despite its relatively uncivilized manner, the Mach IV’s high power and low weight produced a fastest lap time that exactly tied the Z1 for first place—44.5 sec.
Our Ducati’s huge wheelbase and nearly thirty-one degrees of steering rake made it feel a bit clumsy in the two slow low-gear corners but completely stable and carefree in the faster bends. Incredible lean angles are possible on the Duke, but poor tractive ability of the Metzeler rear tire cost it dearly in the fast corners. Just when it was time to be getting on the gas in earnest, while exiting a corner, the tire would drift and slide alarmingly. With the wind drowning the gear whine from the engine, the only noise from the bike is a pleasant cadence from the pipes. You sit back behind the long, swept-back handlebars; it’s like being in remote control. Clutch, throttle, and brake function were perfect. Lap time was 46.4 sec. for fifth spot.
Norton’s suspension control, tire adhesion, and lean angle were all great. The engine peaks out at 7000 rpm and has a flat, loafing feel. Commandos are very un-frightening to ride fast. Our only moment of concern came during heavy braking in sweeping corners: the front end wallowed a little, probably because the fork angle is getting fairly steep at that time. The Avon tires felt vastly better than those on the Ducati. Time was 45.6 sec., good enough for fourth place.
Triumph’s time-tempered Trident was a lot smoother than it used to be; the footrests and the sides of the fuel tank are the only spots that continued to buzz enough to cause notice. They’ve put a set of high-rise bars on the 750 triple that look exactly like the ones that used to come on the old BSA Road Rockets. The Dunlop TT-100 tires felt perfect while the machine was muscled through the tight corners and held wide open around the sleepers. The footrests were the first things to ground, and since they are the non folding type, they limited cornering to a major extent. Shifting and braking were both effortless tasks on the Triumph. Its shift lever only moves a half-inch during a shift. The pipes make an absolutely beautiful sound at the 8500 rpm shift point. Despite the third-place time of 45.3 seconds, the Triumph offered the best combination of cornering ability and low scare factor.
Harley-Davidson’s Sportster was ham-strung by a rear tire that was as limiting as the one on the Ducati. The Goodyear skins are the only ones in the world that will fit H-D’s new safety rims. Ostensibly the rims will not let the tire distort enough to cause a crash if a blowout or sudden flat occurs. But the tires have squarish corners that distort and cause a host of weird antics during hard cornering. Suspension feel was perfect, as hard as we could push the bike with its squirrelly tire. Some problem was experienced with the caliper dragging on the disc after it was used hard for a few laps, but the brakes continued to stop well. An awful lot of clanking and rattling and general commotion came out of the engine around the course, and the oil pressure warning light winked at the rider the whole while. The oil tank is positioned so that it jabs into the rider’s right thigh and the oil gets blisteringly hot during hard runs. Although displacement has been increased to an even 1000 cc, the new California legal mufflers effectively neutralize any power gain that might have been realized. Time for the Sportster was a last-placed 48 seconds even.
That was that for the second day. Acceleration testing was next.
Primal battleground for Superbikes: the drag strip. John Swartzlander had his immaculate CB-750 ready first. In Cycle’s first Comparison Test, the Honda had been the only entrant capable of pulling a drag slick; consequently it rolled to the line this year with an Avon gumball on the back. It was too much tire for the Honda. Easily the most civilized, most mature motorcycle in the comparison test, the CB-750 was penalized both by its soft clutch springs and by its whisper-quiet and restrictive mufflers. The snap it had in 1970, that allowed the bike to cope with an Avon slick, is gone in 1972. Off came the gumball, on went the stock Dun-lop, and the Honda came up with its best times on the fifth and seventh runs: 100.67 mph in 13.485 seconds. There didn’t seem to be any sense beating it to death—only nine runs were made in all—and the Kawasaki 750 was parked.
The Ducati was next, and proved with its early runs that it would be, along with the Trident, easier to ride than all the rest. Its torque, its buttermilk gearbox, and its willingness to run dead straight down the strip were the reasons why.
When the bike was tested in the October issue of Cycle, clutch difficulties stood between it and its best times. This time the legendary A.J. Lewis has seen to any clutch bothers: release was crisp and accurate, and engagement was solid. With stock gearing and a stock tire the black Duke hustled to times of 13.289—101.12 mph. The engine’s torque made wheelspin easily controllable, and once the rider learned not to overshift from first to second the gearbox’s smoothness and accuracy became a revelation.
The Ducati makes useful horsepower up past 8500 rpm; shifts were executed at an even 9000. Lewis experimented all day with different final drive ratios, but the standard gearing gave the best ET and terminal speed. In all, 20 runs were made: five were at 100 or better, nine were at 99, three at 98, and three at 97.
Next came the Triumph Trident, a bike that had run 12.78—103.92 during the 1970 test and was facing this year the same kind of muffler restriction that had slowed the Honda. But the Trident was more than up to the task. Its fabulous five-speed gearbox, Bob Ellison’s tuning, and gearing that yield-ed 105 mph at 8000 in top produced two 12.72s and one 12.718 in eleven runs. Its best terminal speed was 106.00 mph, more than 2 mph faster than it had run in 1970. Discarding two familiarization runs at the outset and one warm-up run at the start of its second session, all eight of the Trident’s quarter-mile efforts were in the 12.7 range. It was the most perfectly-geared motorcycle in the test and looked at the outset to be capable of 12.6 or high 12.5 quarters. It never had a chance to explore those capabilities. Second gear shredded on the Trident’s twelfth run, just as it was beginning to respond to Ellison’s fine tuning.
Up next was the 750 Norton Commando. Its ancestor had out-ET’d the field back in 1970 with a pass at 12.69 and had finished behind only the Kawasaki 500 and the Trident in terminal speed. It had been specially setup for the quarter-mile by Harold Allison; it was legal, but just barely.
This year’s Commando, while it had been beautifully prepared by Bob Yacenda and Brian Slark, was stock, right down to its gearing and tires. And while it was stronger on the top end the alterations to its engine (effected to help keep it quiet) have hurt its E.T. The Norton’s very first run produced its fastest speed: 104.77. Its quickest ET, 12.896, came on its second pass. Eight subsequent runs produced only one ET in the twelves, and terminal speed stayed in the 101-102 mph range.
This Roadster, like three others, Cycle has tested, had a very peculiar characteristic: when engine temperature rose past the nor-mal highway operating range, the bike would pick up a surging condition that penalized it in the higher gears. Even so the 750 gave a superb account of itself. It was easy to ride, wheelspin was controllable, and shifting was as light and accurate as it had been during the 1970 comparison. Like the Sportster, it has a four-speed transmission. Another gear would have helped.
Out next was the 750 Kawasaki Mach IV, a bike that’s in hog heaven at the drag strip—if you know how to ride it. In the first place, it doesn’t perform at its absolute best unless the engine is well below normal operating temperature. In the second place, while the engine is willing to rev, best times are produced by shifting early – like at 7000 rpm or just below. In the third place, a balance between engine speed and clutch engagement must be struck or the Mach IV will either spin the rear tire hopelessly or head straight for the moon. In the fourth place, the rider must locate himself as far forward as possible to keep the front end of the two-stroke Kawasaki on the ground.
The Mack IV is difficult to deal with in a maximum acceleration situation. It attacks the quarter angrily and traverses it in a series of quick, furious, hopping convulsions. Like the Kawasaki 500 the engine is located back in the frame, and it’s located high, both of which conditions assist weight transfer but make it tough to keep the front wheel close to the pavement. Too, it keeps the rider busy. The shift from first to second must be made at a time when the bike is still trying to do a wheelie, and it bolts out of the gate so hard that moving your feet up to the footpegs is a major effort.
A suitable technique was discovered by the third run. Three-quarters throttle through first gear, light clutch-slip, and shift executed at 7000 rpm, produced a heart stopping run of 12.283 at 110.29 mph, mufflers, air-cleaners, stock handlebars and all.
The Mach IV had the most willing and the most hysterical engine in the entire test. It is often difficult to wind a motorcycle’s engine up to 7000 or 8000 rpm and then gas it wide open and drop the clutch. It’s unnatural and it’s abusive, and it makes you cringe inside. But the Kawasaki engine rockets to 7500 rpm at the touch of the throttle; nick it and it comes at your throat with a cacophony of ringing fins and slapping pistons and horsepower unrestrained. The Mach IV demanded the most attention at the drag strip. It was also the most fun to ride, a wild and skittish bucking bronco with all the talent in the entire world and not one single ounce of condescension.
Its big brother, the incredible Z1, was next. Unlike the Mach IV (Murphy had tightened the final drive ratio from 3.13 to 3.21), alternative gearing is not as yet available for the 903—it was as stock as a motorcycle can be. When we tested it for the November issue new pistons and rings had just been fitted, and although it produced fabulous times of 12.52—107.52, it was smoking heavily, for the Comparison Test the rings had finally seated and the bike began to give an indication of its true potential. It only mad four solid runs. The first was 12.429—110.42. The second was 12.415—110.02. The third was 12.386—110.42. And the fourth was 12.397—110.70. For all its civility, for all its weight, and for all its smoothness, the 903cc Z1 produced the strongest top-end of all the Superbikes, and its ET was only a tenth of a second slower than the Mach IV. And it never made what its rider considered to be a perfect run, because the line between perfect traction and hopeless wheelspin is a particularly fine one. Before “the run that never happened,” the Z1 blew an enormous cloud of oil-smoke out its tail pipes. The rest of the mechanics gathered at the starting line and were asked if they would permit the Z1 to leave the grounds and be disassembled back at the distributorship. While mechanic Jeff Shelter and Public Relations Director Skip Newell were prepared to undress the Z1 on the spot, the rest of the participants felt that that was unnecessary and the 903 headed back to Santa Ana.
There was nothing wrong with it. Expecting the worst, Shetler and John Bridges pulled the cylinder head—nothing. They pulled the cylinder assembly—nothing. Finally they said the hell with it and dismantled the engine completely. They could find nary a blemish, but they did notice an accumulation of oil in the plenum, and into the combustion chambers. Scratching their heads they reassembled the Z1 and delivered it to Cycle’s Westlake Village shop facility the next morning.
With only four solid runs under its belt it is entirely possible that the 903 could have improved its ET by as much as a tenth and a half or two tenths, with no alterations at all. With a gearing swap (the 903 was just barely setting into fourth before the traps) it should be able to run at the 12.1 range with no trouble. And if the bike had not blown that huge cloud of smoke, and if the Kawasaki representatives had felt like it, they could have installed their other rear wheel assembly—the one with the M&H 321 slick on it—and they might have seen the first box-stock 11-second run.
On the other hand, even if the Z1 had continued to run, Kawasaki might have been reluctant to fit it up with a gumball and shoot for the elevens. It is conceivable that they don’t want the tractability and the finesse of the 903 to be overshadowed by its acceleration figures; while it can chew up a drag strip quicker than any motorcycle in history (save the muscle-bound and foaming Mach IV), it can do other things even better.
Finally the Sportster, the Superbike with the Superbike image. Of all the bikes in the test, the Sportster needed a high-traction rear tire the most. Extremely quiet mufflers necessary for 1973 have damaged its high-rpm horsepower capabilities. But its gargantuan low-end torque remains, and a tire could have taken advantage of it. With the stock Goodyear 4.25--18 on the back the Sportster had to be tip-toed out of the hole to reduce wheel-spin—but once into the up-per reaches of the power band there simply wasn’t a lot of urge left. Despite a punishing 22 runs the best figures for the Sportster were 13.393—99.88 mph.
In addition to the characteristics of the rear tire there were several factors that kept the Sportster from being as enjoyable, and as potent, on the drag strip as it might have been. In the first place, the chopper handle-bars make it difficult to move around on the bike, and they make it difficult to crawl out of the wind. Secondly, the tachometer seems so random in its movements that precise shifting speeds are hard to establish and impossible to duplicate. And third the long, wide gap between third and fourth (of a four speed transmission) pulled the engine down away from its power peak as the bike was nearing the traps. Its best performance resulted from no clutch slip and speed-shifts at 6600 rpm. The Sportster was uncannily consistent for the entire day. Of its 22 runs, ten were in the 13.5 second area, and six were in the 13.6s. Seven were at a trap speed of 99 mph, and nine were in the 98s. It was clearly not as potent as its 883cc 1970 predecessor had been (12.97—102.15), but it was just as clearly more legal.
From Orange County the test moved to headquarters of Yamaha International in Buena Park, California. We needed accurate, unbiased rear-wheel horsepower and torque figures for the Superbikes. Yamaha had a dynamometer, and they had Bill Stewart, who knew how to run it.