$1000 Sportbike Surgery

Source: Motorcyclist, January 1996

Supple suspension and burly brakes give Kawasaki's ZX-11 twisty road manners to match its straight-line speed.
Nine out of ten ZX-11 bull sessions around here begin with celebrating its 131 horsepower and 175-mph escape velocity. But the tenth invariably berates the bike's harsh, uncontrolled suspension and fade-prone brakes. So after five years of waiting for Kawasaki to cure the Maximum Ninja's afflictions, we set out to doctor them ourselves.
For starters, we wanted enough linear, fade-free stopping power to match the ZX-11's triple-digit proclivities. Even the grippiest aftermarket brake pads alone weren't enough. Reining in 601 pounds of Ninja (that's an 800-pound projectile with a full-size rider on board) generates more heat than Kawasaki's heat-treated stainless steel rotors can dissipate. Working against standard sintered-metal pads, hard-core backroad antics generate enough heat to fade or even warp stock ZX-11 rotors.

To dissipate 175-mph heat more efficiently and generate more consistent stopping power, we cued up a set of Ferodo ductile iron (that's ductile as in malleable, as in more likely to bend than crack or break) brake rotors ($535 including brake pads and hardware).
ferodo rotor The rotor swap is reasonably easy if you know a die grinder from a blow dryer. Still, follow the directions to the letter and triple-check everything.
Extra care now can prevent big trouble the first time you reach for the lever. If you're not comfortable with the process, have a pro do it.
Grind off the stock rivets to remove the stainless rotors, then mount new iron "blades" on the standard aluminum carriers using new buttons that come with the kit. Presto! Race-spec floating rotors. It takes a few miles for the new pads to chew through the anti-rust zinc plating to bare iron be neath. Once the swept area shows clean iron, popping the pads out to scrub off any accumulated zinc (try emery cloth spread over a hard, flat surface) accelerates the bedding-in process.
Though they're rated to survive 1100 degrees Fahrenheit, Ferodo says the semi-metallic C.P. 901-compound pads run cooler and are kinder to rotors than the average sintered-metal equivalent. No worries about "Racing" in big letters on the package. Ferodo recommends their less aggressive (and less abrasive) SuperSport-compound pads for streetbikes with stainless steel rotors. You could use C.P. 901-compound pads with stainless steel rotors. Still, the ductile iron works much better.
Even so, prepare to be slightly underwhelmed for the first few stops out of the garage in the morning. Even warm, initial bite is slightly less immediate than fresh, stock ZX-11 brakes. But from there, the new setup seems to thrive on heat rather than wilt under it. Spreading impressive power over a broader band of lever travel, the Ferodo brakes have a more linear feel than stock, making it much easier to feed in just the right amount of stopping power in any situation. They're never grabby. And shy of outright abuse, they don't fade either.

left fork adj preload Gold Valve
Onward to the suspension ward. The easiest way to make the ZX-11's alternatively harsh and mushy damper-rod fork behave itself is to slide in firmer fork springs, followed closely by a set of Race Tech Cartridge Fork Emulators ($124.95, plus two pints of your favorite 15W fork oil).
With the patient opened up on the table, we traded the flaccid 0.83kg/mm ZX-11 fork springs for stiffer, straightrate 0.92kg/mm Race Tech units ($89.95). And since each stiffer, straight-rate fork spring is shorter than the progressive coil it replaces, a steel spacer takes up the slack. An Emulator transplant is more complex than just swapping springs, but anyone with reasonable mechanical aptitude, a good set of tools and opposable thumbs can handle it. Instructions are first-class, as is the installation video that comes with the kit. But what if you read the instructions, watch the video, then get everything apart and still panic? Then there's a calm voice at Race Tech's tech support hotline to talk you down.
On the Eleven, defeating Kawasaki's external rebound damping adjusters complicates installation a bit. Let somebody else handle the brazing if you're welding-impaired. Race Tech does the job for $15. Otherwise, if you can change fork seals, you can probably install the Emulators.
What you get for your time and money is more precise, more adjustable rebound and compression damping. The Emulator-equipped fork controls rebound damping with fork oil viscosity; 15W in this case. Meanwhile, varying the Emulator valve's adjustable spring and bleed hole lets you tune low-, mid- and high-speed compression damping to taste. The only downside is the lack of external damping adjustments. You'll have to spin off the fork caps, slide out the springs and fish out the Emulators to make changes. Adjustments take about 15 minutes after a little practice.
Heading aft, the main problem is inconsistent damping from a painfully basic KYB emulsion shock. The air/oil meringue flowing through its stock valving, you see, is inherently variable, and the design of the stock shock's damper piston limits the amount of tuning you can do. The net effect: Dreaded High-Speed Wallow at prime roosting velocity. The fix is another type of crafty Race Tech valving gear.
Rather than burn the limited budget with a new shock, we tried Race Tech's 40mm Gold Valve Shock Kit with a remote reservoir ($259.95, plus $24.95 for one quart of shock fluid). To keep the shock body's soft aluminum bore from wearing away and contaminating the damping fluid, Race Tech hard-anodized ours ($55) to keep damping consistent over the long haul. From there, one shock doesn't fit all, so Race Tech sets up each kit according to your bike, your weight and riding style.
The stock ZX-11 spring was perfect for our 200-pounder. So $340 and some sweat buys a fully adjustable, rebuildable, remote reservoir diaphragm rear shock. Remember, it's shock surgery, not brain surgery. Between the instructions, the video and tech support line, it's actually a little easier than our fork work. Once the shock is buttoned up, you'll need a source of high-pressure nitrogen (200 psi) to charge the reservoir, as well as a pressure gauge capable of adjusting small-capacity/high-pressure settings. If you're still queasy about the whole thing, Race Tech will install the kit for another $85.

Gold Valve spring
OK, wash your hands. It's time for a little fine-tuning. We set sag at 37mm up front and 33mm in the rear; a little firmer so the chassis stays balanced as it squats under power. (See our July '95 issue, p. 70 for the full rundown on setting sag.) Our Secret Suspension Test Loop told us baseline damping settings were better suited to a smooth racetrack than public pavement. Thus we factored some compression and rebound damping out of the shock valving for more compliance at street speeds, setting the compression damping 15 clicks out and rebound at the second of four positions. Up front, we reduced preload in the standard 64-pound Emulator springs from four turns to one-half turn.
dunlop sportmax At that rate, the ride is taut, but comfortable. On surface streets, all but the nastiest craters are effectively erased, as are most freeway expansion joints. That controlled, compliant feel continues through the twisty bits. Cranked over in a fast, bumpy corner, the Emulator-equipped fork impersonates pricey aftermarket cartridge forks, tracking an appointed line that would have the stocker chattering and threatening to run wide. Sharp-edged bumps are no longer fed straight into the chassis, boosting confidence.
Add accurate damping from the re-valved shock, and the Maximum Ninja is dead-stable carrying large speed through long sweepers. No more wallowing, grasshopper. just more comfort, more compliance and more front-end feedback, even at full-tilt lean angles.
So where does that leave us? Those of you obsessed with such things have already figured we blew our budget by $100. So we won't tell you about the extra $320 we spent on new D205 Dunlop Sportmax Touring radials that stick famously and hardly look worn at all after 2200 miles of hammering. These are great skins.
We'll say this much, though. It doesn't matter where you ride or how quickly. Suspension and brakes worthy of The Engine make that 99.9 percent of the time you can't pull the 175-mph trigger almost as much fun as the 0.1 percent when you can. Almost. And that, boys and girls, is a certified bargain. Even if we blew an extra C-note or so to do it.

Quadrant ZX-11 Street Shock
The British Bolt-On Alternative

We were looking for another solid, sub-$400 shock to test in this Surgery deal when thunk!-an EMC Dynamics' Quadrant ZX-1 I shock tumbled out of the mail bag. Okay, then.
On paper, the Quadrant looked interesting enough. Though it uses a less pricey steel body rather than aluminium (steel is notas adept at dissipating heat), the Quadrant is fully rebuildable and, according to Quadrant, fully adjustable. Rebound and compression adjustments, which work through a single knob, are integrated through the use of a twin-tube internal damping apparatus similar to that of a cartridge fork's internals.
There's also, says Quadrant, an internal "gas cell" for (theoretically) more consistent damping. And priced at $395 including spring, the price was certainly right.
Once mounted on the bike (a 1.5-hour job on the ZX-11, notincluding bad words and throwing things), we set spring preload via the Quadrant's threaded adjuster (which is almost inaccessible on the ZX). At least the rebound/compression adjuster's large knurled knob is readily accessible, allowing roadside damping changes sans tools. But no detents through the 5-turn adjustment range and no marks on the knob itself make precise changes tedious.
The standard spring rate (Quadrant offers various alternatives) is aimed at riders between 143 and 209 pounds -right in the ballpark for most of us. Once adjusted to taste (we prefer 25 to 35mm of sag), the Quadrant delivers a controlled, well-damped ride that's more comfortable and compliant than the stock ZX-11 shock.
But stuck between 601 pounds of ultra-quick Ninja and a few hours worth of rough tarmac, the Quadrant's damping still fades enough to let the rear of the bike move around more than we'd like. The single adjuster had marked effect on rebound damping, but did little to alter the compression side. It's not quite a match for our more sophisticated Race Tech conversion in terms of pure performance. However, the Quadrant does offer more control and a better ride than the stock ZX-11 unit as well as many original- equipment shocks-at a reasonable price. For those with some extra cash to spend, Quadrant also offers a higher-performance, remote-reservoir race shock for $595. But if you're looking to upgrade the average sportbike's rear suspension without evacuating your wallet, the Quadrant is a viable alternative.