It was with great reluctance that we returned our Z1000 project bike back to Kawasaki. After two years of tinkering in our garage we had transformed the green meanie into an even more potent streetfighter.
Well, it’s finally come to an end. After more than two years of faithful and exciting service in the MCUSA garage, our charismatic Z1000 has gone back to meet its maker. But not before we turned it into a real backroad burner with a thoroughly tweaked suspension.
Our Z1000 project received a healthy dose of composure and improved ride quality that transformed a somewhat sketchy ride into one that inspired confidence in its rider. Credit the brainiacs at Race Tech, the suspension gurus who modified the stock components to yield the kind of control usually reserved for pricey aftermarket bits.
It all began at a Tony Foale suspension seminar when I showed Race Tech’s head honcho, Paul Thede, our project Z. I related to him a general unbalanced feeling that I couldn’t tune out with the available suspension adjustments: spring preload and rebound damping but no compression on both ends.
The balance issue seemed to be originating at the rear end, and this was most evident when we had the Z at a trackday. We were unable to achieve the correct balance of rebound damping, as it always seemed either too much or too little for the spring. At the front end, the fork suffered from a dearth of rebound damping.
Thede, hearing these comments and looking over the Z’s stock suspension components to pronounce them worthy of modifying, promised he could help and extended an invitation to come to Race Tech’s Corona, California, shop.
We met Race Tech’s Paul Thede (right) at a suspension seminar, where he offered his expertise in correcting the Project Z’s unbalanced feel.
In addition to the suspension issue, the Z also exhibited a slightly unbalanced feel through its steering and was very sensitive to tire profiles. In an effort to track down the root cause, Race Tech decided to throw the bike in front of its Computrack coordinate-measuring machine. For a $150 charge, the Computrack apparatus measures geometry points to reveal accurate data for rake, trail, wheelbase and swingarm downslope, among others. (It’s also an excellent tool for straightening out frame twist, a surprisingly common ailment among even new motorcycles.)
The Computrack machine was invented by Aussie Greg MacDonald, and included with it are MacDonald’s parameters for optimal geometry, something he calls his “sweet numbers.” In a nutshell, MacDonald likes a steep rake for quick steering but a copious amount of trail for stability and front-end grip.
In the case of our Z1000, Race Tech’s Andy Glomski measured its rake at 24.6 degrees, a fair bit more relaxed than the 24.0 degrees Kawasaki claims. It’s possible that the aftermarket tires on our bike were largely to blame for the discrepancy. This might also help explain the nearly-5mm extra trail over the factory’s spec of 102mm. Its wheelbase, too, measured longer than stock assertions, with 56.4 inches between its axles instead of the 55.9 inches in the Kawi brochure, perhaps a result of chain stretch from countless wheelies.
In order to get more desirable geometry numbers, the Race Tech crew performed a mild optimization on the Kaw, a $500 upgrade. (Comprehensive optimizations such as fitting new triple-clamps or tilting steering-stems ups the cost significantly and are primarily for racing.) In our case, lengthening the Z’s shock 6mm and keeping the front ride height stock resulted in rake and trail numbers that were both reduced; the swingarm pivot height was raised 9mm.
When it comes to suspension tuning, Race Tech has built an enviable reputation in the industry. Like most successful people, Paul Thede fully immerses himself into his business. The Tony Foale suspension seminar mentioned earlier was an indication Thede continues to thirst for knowledge, and this was backed up at a trackday following the seminar where he was experimenting with a custom data acquisition system to measure suspension forces. Though Race Tech was founded on dirt bike suspension tuning and Thede is an avid dirt rider, there he was, scuffing knee pucks and wrenching the R6 himself – all in an effort to learn more about sportbike set-up.
As for the suspenders on our project bike, the transformation began with new springs to match my 150-lb geared-up weight and riding style. According to the experts at Race Tech, the stock fork springs were too soft and the shock spring was too stiff.
Our project Zed’s wheelbase was stretched out a half-inch longer than the claimed factory spec. Do you suppose a few hundred wheelies might’ve stretched the chain?
The Z1000’s Showa fork is a bit unique in that its damping circuits for rebound and compression are found only in one fork leg. Some might think this to be a potentially problematic design, but Thede says that it’s fine as long as the front axle is stiff. Our bike received 0.90 kg/mm springs in place of the stock 0.85s. The amount of oil in a fork also contributes to its behavior, and the stock 110mm of 5-weight fork oil was duplicated but with Race Tech’s proprietary oil blend. To achieve better damping qualities, the fork was fitted with a Race Tech Gold Valve kit.
Out back was an odd situation. Thede explained that Japanese bikes formerly were equipped with shock springs too soft for heavier American riders, but now they are going too far the other way, especially on bikes that are expected to carry a passenger. The rationale is that it’s better to have too stiff a spring than one too soft, as a more yielding spring can cause dangerous instability. That being the case here, it’s no wonder the suspension couldn’t be adjusted appropriately for my puny weight.
The Z’s stock spring was progressive, ranging from 9.5 to 10.5 kg/mm, working through a linear-rate shock linkage. For our bike we used a straight-rate 8.9 kg/mm spring in conjunction with a Gold Valve shock kit to alter the rebound and compression damping circuits.
Bolted back together and with spring preload set for my weight, it didn’t take very long in the saddle to notice a huge improvement in ride quality. Harsh-edged Botts Dots that used to jar the chassis were now absorbed with plush precision, yet improved wheel control keeps the bike better planted, especially over larger bumps.
Race Tech modified the front suspension by replacing the stock 0.85 kg/mm springs with 0.90 units, adding their own special blend of oil and fitting a Race Tech Gold Valve kit.
But the effects of the Race Tech work goes beyond just that of wheel control. Easily as impressive is the newfound balance of the Z’s chassis. The bike now seems to work its wheels in congruence instead of bouncing from one end to the other. I ended up taking out one turn of rear preload from Race Tech’s setup and didn’t feel the need to tweak anything else for the rest of my time with the bike.
As for the Computrack optimization, that’s a tougher nut to crack. The bike definitely improved its handling, but how much of that was due to a well-tuned suspension and how much to the slightly tweaked chassis geometry is virtually impossible to definitively ascertain.
All I can say is that the overall effect was dramatic, and this was the best modification we made to our project bike. Consider the $750 cost of the suspension work a real bargain, and it’s backed up by Race Tech’s guarantee – any valving changes will be performed free of charge for 90 days. (Full pricing details are listed below.)
It’s A Wrap!
The Race Tech crew went to work on the rear shock by swapping out the stock progressive spring for a straight-rate 8.9 kg/mm spring with an accompanying Gold Valve shock kit.
The best thing about the Z1000 is its character. All those Ducati, BMW and Harley snobs who claim that Japanese bikes don’t have personality have never ridden the Z. The green meanie practically begs its rider to hammer on it. In terms of angels sitting on your shoulder, the Z definitely isn’t the nice one. It’s always egging on its rider to do something silly like hacking out the back end. Unintended-but-not-quite-prevented wheelies ensue, plus the normal kind.
This characteristic is accentuated by the nasty growl from the Leo Vince titanium exhaust, smooth throttle response from the Techclusion fuel-injection controller and improved braking performance via flex-free Kevlar brake hoses from Goodridge. The ti exhaust system added the obvious visual bling, but the bike’s appearance was also nicely cleaned up with a Targa Accessories fender eliminator and turnsignal kit, front signals from Lockhart Phillips, and a carbon fiber front fender from Carbonworks.
One of our favorite accessories is the Laminar Lip mounted to our Z’s teeny flyscreen. It’s proved to be an ideal combination of supplementary wind protection while not adding a visually obtrusive blemish to detract from the Z’s edgy good looks. Windblast hits my 5’8″ body in the upper chest area, making 80-mph freeway jaunts fairly composed. I removed the Lip after a year and found the resulting lack of protection annoying along with a noticeable increase in wind noise.
The Project Z1000’s handling improvements after the Race Tech adjustments were well worth the $750 cost. If you look closely you can see Duke grinning.
There are just a few more aspects I’d like to improve before I pronounced the bike perfect. Although the Z’s seat isn’t bothersome for the shorter jaunts I would usually use the Z for, and the cutaway near the tank helps make the bike feel smaller than it actually is, its forward section is too narrow for good support over long runs. In addition, the Z1000 creates lots of vibration above 5000 rpm, transmitting it to the rider mostly through the Z’s aluminum handlebar. We’ve heard positive reports about the Bar Snake, a vibration-damping handlebar insert, but we ran out of time with the bike before we were able to install it.
So, through more than 10,000 miles, our Project Z sucked up all the abuse we could throw at it, emerging from our mistreatment without failure of any kind. A clutch that got grabby with a narrow engagement point was the only thing close to a mechanical issue, and that was due more to the cruelty of our hands than any design deficiency. One issue we’ll take up with Kawasaki is the factory’s claim of a 4.8-gallon fuel capacity. Twice we ran out of gas during our two years with the big Zed, and twice we were able to squeeze in only 4.1 gallons of fuel. On a related note, the Z’s fuel mileage ranged from 30-42 mpg, averaging just over 35 mpg.
Parting was such sweet sorrow…
When it came time to return Mr. Z,
Editor Duke Danger’s heart said to
give the green meanie a good
home in his own personal garage,
but the bank balance said otherwise.
Here’s his standing ovation.
We would’ve been sad to see our Z1000 returned at any time, but it was almost impossible to give back after the suspension tuning that transformed the bike into a much more composed and balanced ride. I’m still kicking myself for not being able to come up with the necessary funds to park it permanently in my garage.
Mr. Z, we miss you.
Race Tech Suspension Parts List
Fork Gold Valve: $154
Fork springs: $109.99
Fork Oil: $37.47
Rebuild fork: $65
Shock Gold Valve: $154.99
Shock spring: $109.99
New shock collar: $12.99
Shock rebuild: $105
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