The inline four-cylinder engine sported a more oversquare 75 x 50.9mm bore/stroke configuration than the previous generation (2mm larger bore, 2.8mm shorter stroke). This allowed the lighter crankshaft to spin higher (12,500 rpm versus 11,500 rpm for the old model) and fit bigger valves, up 1mm on both the intake and exhaust compared to its forerunner. Kawasaki also employed more aggressive cams although compression remained the same at 11.5:1.
Kawasaki's pioneering development of ram-air technology to boost power continued with the latest generation 9R, with twin ram-air intakes just under the front headlights helping to increase airbox pressure at speed. The fueling was handled via a quartet of Keihin 40mm carburetors, equipped with throttle position sensors that were part of the K-TRIC (Kawasaki Throttle Response Ignition Control) ignition system. Not only did this setup optimize ignition curves by monitoring throttle position, but also the rate of throttle opening. The result was better fuel economy (about 40 mpg) as well as improved throttle response and less detonation at low rpm.
While everyone else was going...
While everyone else was going to inverted forks up front, Kawasaki stayed the course during the ZX-9R's tenure, using a beefy 46mm conventional cartridge fork from '98 on. Six-piston calipers biting on 296mm discs provided excellent stopping power for its time.
The Ninja also had good brakes, with Tokico six-pot calipers and 296mm front rotors. The fork was a conventional 48mm cartridge fork-lighter than the inverted forks of that era-utilizing adjustable preload, compression and rebound damping, with the rear single shock sporting similar adjustment capability. The rear wheel was a 5.5-inch-wide unit while the front was a 3.5-inch-wide hoop, both in 17-inch diameters; stock tires of the day were Bridgestone Battlax BT56, with a size 530 o-ring chain transmitting power.
In 1998 the bike retailed for $9999 making it a solid deal compared to the over $10K of the Yamaha R1. Pricing on the bike stayed flat until 2000, when it bumped up to $10,199 then in 2002 it dropped all the way back to $9499 and stayed there for 2003 as well, no doubt a sign of its future.
All generations of the ZX-9R...
All generations of the ZX-9R came with this huge exhaust muffler, but starting with the '98 model, the canister was made from titanium for less weight (although California models had to use stainless steel due to the catalyst inside). Thankfully the canister was tucked up high for ground clearance.
The 9R received a substantial makeover in 2000. Changes included better midrange power output via new intake camshaft profiles and longer intake ports, as well as a new cylinder head design that bumped the compression ratio up to 12.2:1. The carbs were updated to new Keihin CVRD 40mm units that used flat-design vacuum slides breathing through a larger ram-air scoop underneath the headlights, while the exhaust system sported larger and longer header pipes for increased top-end breathing. Other internal upgrades included electro-plated aluminum cylinder bores, faster 16-bit ECU, stronger piston pins, lighter cams and clutch gears, and a new shift drum with re-shimmed gearsets sporting undercut engagement dogs in 3rd and 4th gear to quell shifting complaints with the '98 model.
The rear subframe was changed...
The rear subframe was changed to aluminum and bolted on instead of welded in '00, dropping weight and easing repair bills in the event of a crash. Rear shock ride height adjuster was now threaded instead of using shims.
The chassis was beefed up for increased rigidity, with 10mm taller main spars and a 12mm-longer steering head tube. The swingarm featured internal ribbing for more strength, with larger-diameter (25mm versus 20mm) swingarm pivot and axles. Suspension damping and spring rates were revised, with the rear suspension linkage getting a more linear rate for better action over big bumps; the triple clamps received 5mm less offset for more trail and increased stability. The front brake rotors were increased to 310mm, with the rear wheel width expanding to 6.0 inches, and weight dropped by a couple of pounds. Unfortunately this meant the Kawasaki was still about 20 pounds heavier than the R1 or the Honda CBR.
The 2002 model year arrived, and one final upgrade was made to the ZX-9R. Front brake rotors were once again increased in size to 320mm. The crankshaft weight was increased by 10 percent to help smooth power output, with the 40mm carbs getting some minor updates. Chassis was stiffened with different engine mounts, and a swingarm brace was added; the drive chain was shrunk to a 525 from the previous 530. Weight, however, grew by about 10 pounds.