Big Dogs: Uncorking the 'Busa and ZX-12

We love a challenge around here, whether it's keeping Kento in sight through a particular set of twisties or simply turning in a story on time (for a change). The proverbial gauntlet was thrown then, when our ZX-12R moaned past the radar gun at a measly 185.6 mph, and the Hayabusa-a bike we damn well know is capable of 190 mph-could only manage 183.9 mph. With a tailwind. At least it verified something sportbike aficionados have been fearing for more than a year now; under the threat of government-imposed speed restrictions, manufacturers have voluntarily limited their flagship machinery to 186 mph, or 300 kph.

To add insult to injury, a trip to the dragstrip sees both bikes leaving the line in some sort of sick Michael Jackson dance parody, jerking and shaking as their clutches alternately grab and release. It's like watching a grown man struggle with tying his own shoelaces-you want to help, but don't want perform the indignity of going to his rescue. We couldn't resist, though. The big Kawi and Suzi were made for straight-line performance, and just begging for some simple mods to help them to unrestricted (see sidebar, page 33) 190 mph-plus top speeds, as well as mid-nine second quarter-mile times. How could we not pick up the gauntlet, thus answering the challenge?

The Hayabusa is an old friend to the SR wrecking crew-189 mph and sub-10 second quarters make for a good introduction-but the Kawasaki was an unknown quantity as we've never had an opportunity to test one until now. Oh yes, we've sat patiently through the bike's delayed introduction and all the controversy surrounding the 2000 model ZX-12R, and the seemingly endless brush-offs in getting a test unit (strange, that-almost like the Kawasaki people knew we'd do something like this) but we're rebels, and won't be denied our performance fix for the sake of satisfying the bureaucrats.

Of course, both bikes were flogged mercilessly in stock form first (ZX-12R, Hayabusa) but the real fun began when the wrenches came out.

Up first, the Hayabusa gained power across the board-and exhibited a smoother curve to boot-with an increase in peak horsepower to 163.2. Perhaps more significant is the big Suzuki's torque (100 foot-pounds at just 7000 rpm) and horsepower spread (over 150 horsepower on tap from 8000 rpm right to the rev limiter at 11,000). The modified ZX-12R's power curve criss-crosses stock up to approximately 8000 rpm, but takes off from there. And while the maximum of 165.7 horsepower is impressive on its own, what's incredible is the engine dances with that peak straight to redline-over a 1000 rpm band of 165 horsepower.

While you'll rarely hear "She can't take much more captain, I'm givin' 'er all she's got," from the ZX or Hayabusa engine rooms, every little bit helps when it comes to all-out top speed and dragstrip performance. Some hop-up modifications were in order if only to ensure that we'd be up against each bike's top-speed restriction and could verify that each had, in fact, been neutered. Exhaust pipes are a given-Muzzys for the Kawasaki and Two Brothers Racing for the Suzuki, and for the intake side of things we turned to K&N Engineering for air filters and Power Commanders. With the pipes fitted and Power Commanders mapped appropriately, a trip to the dyno was in order.

ROAD WORK

In the canyons, the Hayabusa-which doesn't really need any extra jam for the twisty bits-feels decidedly peppier than stock, although its throttle response is slightly more abrupt, especially with the Timing Retard Eliminator (necessary to bypass the top-speed limiter) installed. The Kawasaki, however, is a transformed motorcycle. In stock form, the ZX-12R can be quite a handful, especially if the road is at all bumpy. Its lurchy throttle forces the rider to wait until nearly the exit of a turn to get on the gas. Our modified bike picks up revs cleanly the instant the throttle is cracked, allowing the rider to lighten the front end and make the suspension's job easier over any pavement irregularities. Where the stock bike would flounder midturn, its rider playing with the throttle, the Big Dog ZX rider is on the gas and gone. An amazing improvement over stock and one that makes a Sunday ZX-12R ride in the twisties a much more attractive proposition.

The one unfathomable characteristic of the enhanced ZX is its abysmal fuel economy. While our stock bike didn't get fantastic gas mileage (32 mpg average), our modded Kaw regularly returns in the high 20s. The Hayabusa's mileage changed not a bit post-modification, routinely averaging 35 mpg.

TOP SPEED

With the two Big Dogs suitably derestricted and given newfound steam down below, we ventured to our top-secret, high-desert test site where a slight sidewind put a bit of a damper on the festivities. Our stock, unrestricted numbers of 192.4 mph for the Hayabusa and 190.2 mph for the ZX-12R were obtained at a previous outing, with a slight tailwind present. Nonetheless, our modified ZX-12R first burned past the radar gun at 190.0 mph, with the Hayabusa posting an initial 191.3-mph blast. Gearing can be crucial to top speed, and for that reason we had on hand a selection of AFAM rear sprockets to play with. Dropping a tooth from the rear of the Kawasaki boosted speed to 190.7, but the Hayabusa-geared tall to begin with-couldn't pull anything more and actually lost speed, running 187.1 mph.

It's worth taking a look at both bikes' gearboxes at this point, and how the Hayabusa and ZX make their power differently. The Suzuki-producing a lot of torque over a wide rev band-has a widely spaced box, with first gear good for only 83 mph at redline, but sixth set to a wishful 207 mph. Because it revs just past its power peak in sixth gear at 190 mph (10,250 rpm), adding gearing drops revs off the downside of the horsepower curve, and the Hayabusa can't cope with the lowered rpm.

On the other hand, the Kawasaki-comparatively high revving and with a narrower powerband-has a closer-spaced gearbox with a taller first gear (85 mph) and a shorter sixth (201 mph). Because our modified bike carries its peak horsepower further (right to redline, in fact) it can pull as much gearing as the rev limiter will allow. Helping the ZX in this department is the 46-tooth rear sprocket; dropping a tooth changes gearing only 2.2 percent, whereas dropping a tooth from the Hayabusa's 40-tooth rear sprocket is a change of 2.5 percent.

Popping the mirrors off the Kawasaki (they'd be more at home in something made by Victoria's Secret anyway) netted a further big boost to 193.5 mph, but the same treatment to the Suzuki made no difference. Our guess is that the Suzuki's mirrors, in addition to being smaller than the Kawasaki's units, are closer to the 'Busa's wider bodywork, and thus play a smaller role in the bike's aerodynamics. Additionally, the sleeker Suzuki (see "Tunnel Vision," June 2001) was affected by the crosswind more than the Kawasaki, a not-uncommon trade-off in the top-speed arena.

Once again, the Kawasaki came away as making the most of our modifications, with a top speed of 193.5 mph, while the Hayabusa peaked at 191.3. Certainly, the crosswind played a part, as the Suzuki went faster in stock, unrestricted form than it did post-modification. But every horsepower counts at those speeds, and the Kawasaki's flat power curve at peak rpm played a definite role in its improvement over stock.

Incidentally, we had suspected during our GSX-R1000 test (June 2001) that its top speed was also limited, and we brought our 1000 to the top speed site along with the Big Dogs. Stock, the big GSX-R posted a ho-hum 179 mph, but with a Yoshimura pipe and Timing Retard Eliminator installed, the Suzuki ran 183.4 mph-impinging on stock Hayabusa territory.

DRAGSTRIP

More important than horsepower at the strip is getting that power to the ground, and to that end we further modified our big dogs. In other words, both bikes needed some help in the clutch department if we were to see some good numbers. The Hayabusa incorporates a slipper-type clutch which, while great for street use, grabs like a New York purse-snatcher at the strip. American Performance Engineering (A.P.E.) supplied a one-piece hub, which eliminates the two-piece stock unit, along with a set of plates. While the Kawasaki's clutch is not a slipper-type, it too grabs ferociously at the strip, and we scored a Muzzys hub and bearing which utilize improved oiling (along with fewer, thicker plates) to improve launches.

On the chassis side, Adjustment Tech Racing sent a set of adjustable links to fit the Suzuki, and a Schnitz lowering strap dropped the front accordingly. Already low in stock form, we dropped a shade over two inches from the Hayabusa. Muzzys supplied a set of three-position lowering links for the Kawasaki, and we dropped the front with a regular tie-down. The ZX-12R ended up nearly three inches lower than stock.

Once again, gearing plays a crucial role, and we put a one-tooth smaller AFAM countershaft sprocket on each bike, along with a one-tooth larger rear sprocket. And finally, the stock buns were jettisoned and replaced with ultra-grippy Mickey Thompson MCR shootout tires (DOT buns specifically intended for dragstrip use).

Our man Kent needed just one familiarization run with the ZX-12R before stunning us with a 9.573 second/146.75 mph run, and backing it up on the next pass with a 9.583 second/145.70 mph pass. A huge improvement from the stocker's 9.95 second/144.40 mph best. One look at the timing slips tells part of the story: Stock, the Kawasaki's best 60-foot time was 1.795 seconds, and the combination of the clutch, gearing, lowered chassis and sticky bun were making times in the low 1.6-second range the norm.

In a similar manner, after a single pass on the Hayabusa, Kento posted a 9.688 second/143.62 mph pass before encountering clutch troubles. Turns out someone (we won't point fingers at The Geek, but it was him) didn't soak the porous A.P.E. plates enough before installing them, and they were badly scorched. A quick change back to the stock plates and some stiffer A.P.E. springs, and we were back in business. A couple of runs later Kent laid down a 9.559 second/146.75 mph pass, more than a half-second better than the stock bike's 10.237 second/140.54 mph run. The 60-foot time for the 'Busa had improved from 1.95 seconds to 1.63 seconds.

Turning to the Kawasaki, the day had heated up enough that it was impossible to improve upon the 12R's best run. While these runs are corrected to sea level from Los Angeles County Raceway's 2700-foot altitude, Sport Rider does not normally correct runs for temperature. Utilizing our sister publication Motorcyclist's correction factors, however, both bikes would have been well into the 9.3-second range at 60 degrees.

Top speed or drags, you can choose your poison with either of these Big Dogs and net serious performance gains with little effort. Is 200 mph possible? While that was never our intention, the thought crossed our minds that in perfect conditions (and with a few more aerodynamic tweaks) it is certainly a number within reach. And a half-second improvement at the strip-an eternity in dragracing terms-is just scratching the surface of the potential that lurks inside the ZX-12R and Hayabusa. Of course, now that we've restored their dignity (and then some) there is the question of the turbo kit sitting in Kent's office....

Sidebars:

Derestricting the ZX-12R and Hayabusa
The Contender: Kawasaki ZX-12R
Hayabusa!

RESOURCES

Adjustment Tech Racing
(705) 799-5139
www3.sympatico.ca/a.jones

AFAM U.S.A.
(800) 290-9040
www.afamusa.com

American Performance Engineering (A.P.E.)
(818) 842-4952
www.hayabusazone.com

Black Robotics
www.blackrobotics.com

K&N Engineering
(800) 357-7422
www.knpowersports.com

Mickey Thompson Performance Tires
(330) 928-9092
www.mickeythompsontires.com

Muzzys
(541) 385-0706
www.muzzys.com

Rockland County Motorcycle
(845) 362-1212
www.ivansperformanceproducts.com

Schnitz Racing
(800) 837-9730
www.schnitzracing.com

Suzuki
(800) 828-RIDE
www.suzuki.com

Two Brothers Racing
(714) 550-6070
www.twobros.com

This story originally appeared in the October 2001 issue of Sport Rider.