Sportbikes were massive in the 1980s and 1990s, and the collective knee-dragging consciousness had its nose firmly planted in motorcycle mags, inhaling every line about potent new 400cc machines from Japan. These miniaturized superbikes had it all—ultra-high-revving screamer engines surrounded by top-spec chassis technology of the day, creating a balance of power and handling that punched well above its weight class. It made sense back then. Big hair was matched by big bike sales, and thriving global roadracing scenes meant that fully faired race replicas were the quickest way to a young rider’s heart. But it wasn’t meant to be in the United States, as few of these models would ever grace our shores officially, making the Kawasaki ZXR-400R and its brethren gray-market unicorns.
The all-new 2023 Kawasaki Ninja ZX-4RR tugs at sport riders’ heartstrings by tapping into the same philosophy laid down by its forefathers. Well-armed with its rev-happy four-banger and dressed in sharper components, the newest Ninja slashes through a sea of comparably sized single-cylinder and parallel-twin powered sportbikes, cutting into the growing twins class with its higher specification and $9699 MSRP.
Little bike evangelists have told tales about lightweight sportbikes of yore, and to find out if the 2023 Kawasaki Ninja ZX-4RR is the second coming, we headed off to Thunderhill Raceway Park, in California’s fertile Sacramento Valley, for a thorough track test. Now, let’s get on with the Fast Facts.
- Kawasaki’s all-new 399cc pint-sized screamer is built to do exactly that. A bore and stroke of 57.0 x 39.16mm is a classic short-stroke design, helping this lively mill rev to the heavens, and it’s all bolstered by features we commonly see in Kawi’s performance models. There is plenty of technical gobbledygook pulled from the ZX-6R and ZX-10R Ninja playbooks. A ram-air intake feeds variable-length intake funnels within the airbox, leading to an intake tract designed to be as straight and smooth as possible, improving flow to the precision machined combustion chambers. From there, lightweight forged camshafts actuate 16 teensy little valves—22.1mm intake and 19.0mm exhaust—where cast aluminum pistons and a featherweight flywheel all make this spunky mill shriek toward its 15,150 rpm redline. The bar-style tach does display “16” and even “18,” which stretches the truth but sounds cooler, so feel free to cite those instead.
- Dig into some free-revving goodness. Arguably, there are few better feelings in motorcycling than twisting the throttle, burying the tach into the deep end, and knowing that you can handle every kicking pony underneath you. That statement defines the 2023 Kawasaki Ninja ZX-4RR, which taps into the exhilaration of wringing out big, shouty I4-powered sportbikes without the arm-socket-tugging terror that we know and love them for. Instead, the new Ninja delivers its impressive linear power in a way that intermediate riders can embrace, and advanced pilots will surely command. Between the inviting pull from the bottom and the encouraging note from the 4-2-1 exhaust, you’ll quickly find yourself at the 11.5k mark, where the power starts to trail off due to our North American state of tune. Despite that hiccup, it’s ridiculously smooth, wickedly fun, and instantly memorable from start to finish.
- There’s a sporty gearbox for a sporty steed. Per its price point, the ZX-4RR comes with several premium goodies that models such as the Ninja 400 and its competitors wouldn’t dare boast. Grabbing a gear reflects that reality, as an up/down quickshifter complements a tidy gearbox and the quickshifter works quite well while rowing up through the gears. However, downshifts could use a touch of algorithmic smoothing, though it never once made me reach for the light clutch and go old-school with it. Naturally, you’ve got Kawasaki’s tried-and-true assist-and-slipper clutch to prevent wheel-hop in those hard braking zones.
- You probably caught the North American tune comment, and here’s the skinny. Kawasaki North America and fellow Japanese manufacturers rarely cite performance numbers as a hard rule. Whipping out your Google-Fu will reveal information from other markets pointing to claimed peak figures of 76 horsepower and 28 ft-lbs of torque—measured at the crank. Brand representatives were quite open about the ZX-4RR being restricted above 11.5k rpm due to EPA noise emission regulations, an issue we’ve seen crop up more than a few times in recent years. To be abundantly clear, this isn’t a carbon emission problem, as the triple-catalyzer solution used here is quite clean. Irksome as it may be to not enjoy its full potency in stock trim, Kawasaki feels that the ZX-4RR will appeal to an enthusiast buyer—those who have been around the block a few times and are comfortable having an ECU reflashed.
- We didn’t have to look far for performance fixes. Graves Motorsports has assisted Kawasaki North America in roadracing efforts for the past few years now. As luck would have it, Mr. Graves & Co. were on hand to showcase the 2023 Kawasaki Ninja ZX-4RR’s potential, displaying everything that budding racers or track day junkies can do to bring out the best in their lightweight machines. Related to the restricted stock map, a Graves cat-back slip-on muffler and tune net 76 horsepower and 30 ft-lbs of torque—measured at the rear wheel, mind you—and full exhaust systems pump it up to 80 ponies. Whether you run with a Graves pipe and tune or utilize another performance shop’s solution, the point here is that the aftermarket has responded loudly.
- The riding position splits the difference between committed and comfortable. Hopping onto the Ninja ZX-4RR is a familiar affair. While the rider triangle is a few shades more aggressive than the Ninja 400, it neither takes it to the wrist-aching extremes of your average supersport nor binds your legs offensively. The small I4 packing maintains a slim feel between the knees, while the proportions feel relatively ere towards the smaller side, it isn’t cramped, and I can squeeze my 5-foot 10-inch frame behind the bubble. The touchpoints also befit a bike in this price range. Adjustable levers, quality paint and bodywork, and LED lighting all add up to a commendable bike on that front.
- A respectable electronics package comes to the 2023 Kawasaki Ninja ZX-4RR. Those features start with the 4.3-inch TFT instrument panel featured on numerous models in the Kawasaki lineup. Although I find the UI counterintuitive, the dash looks great and displays everything you could want—there’s even a dedicated Circuit mode with a lap timer. A new ride-by-wire throttle has opened the door for four ride modes—Sport, Road, Rain, and a customizable Rider mode. There is no difference in throttle maps; save for a hint of abruptness during the initial throttle openings, it’s dialed. Instead, the mode primarily adjusts the three-level traction control settings—Sport being the least intrusive, though the others reel in power accordingly. That’s noteworthy, as there’s no IMU to lend assistance. A basic system relying on wheel-speed sensors and preset limits works well. Lastly, you’ve got Full and Low engine power modes.
- A nimble nature is part of the ZX-4RR program. When cruising around Thunderhill and becoming reacclimated, it’s clear that aspects like the short wheelbase and steep rake benefit the chassis’ willingness to flick onto its side. At pace, that eager-pleasing demeanor continues to carry through, where its steel-trellis frame and steel swingarm manage its 414.5-pound curb weight without flexing willy-nilly, holding firm through tough sections like the Turn 2 or full-send Turn 8.
- There are a few considerations regarding the steel-trellis frame. Keen-eyed observers might spot that the subframe is welded in place, just as it is on the Ninja 400, which can be bad news when you take a tumble. That prompts the question of why a lighter aluminum frame isn’t used, given replaceable subframes are commonplace in those applications. Also, a matching aluminum swingarm would save additional weight. The answer is purely economic—materials and skilled labor would increase pricing considerably. The fact is, what we’ve got works well; if you’re focusing on agility, the ZX-4RR is a wise choice.
- Showa suspension is part of the package. We have a 37mm inverted SFF-BP fork repping spring-preload adjustment and a fully adjustable horizontal back-linked BFRC shock—quite like what’s seen on the ZX-10R, though featuring model-specific spring rates and valving. Kawasaki hasn’t pigeonholed the ZX-4RR with an ultra-stiff, racetrack-ready setup, which will surely benefit street riding. Even with my cornfed frame being a bit too much for the springs, the suspenders show courage under fire—it won’t blow through the fork in braking zones. Save for a couple of high-load turns where my heft squishes the shock too much, the ZX-4RR cuts clean lines and eggs riders on to enjoy high corner speeds. You can tip into turns on a dime and get on the gas as early as possible—precisely what you’d want out of a lightweight sportbike.
- We used stock Dunlop Sportmax GPR300 rubber at the track. It isn’t out of the ordinary for manufacturers to throw on race rubber when it’s a track-only event, but we kept things bone stock. The Dunlops held their own at a good clip, although they expressed their limits and did so clearly, thankfully. No one would fault you for thinking that the cast aluminum wheels came from the Ninja 400, though, while curiously similar, they are not the same units. The 2023 Kawasaki Ninja ZX-4RR uses broader rims to accept larger, conventionally sized tires—120/70ZR-17 front and 160/60ZR-17 rear—so many replacement options are available, especially race rubber.
- Radial-mounted Nissin calipers bring on the stopping power. The 290mm rotors, four-piston radial calipers, and an axial master cylinder do quite a bit of heavy lifting. Feel at the adjustable lever is softer, though once you dig into them, they stop the ZX-4RR handily. The KRT Edition seen here—there is no “standard” version in the U.S.—has always-on ABS, which didn’t balk in hard braking zones. There was a bit of pulsing in the lever now and again, but nothing that got me worked up. The fuse box and corresponding fuse are easily accessible for those who get my drift, though I didn’t feel the need.
- The 2023 Kawasaki Ninja ZX-4RR raises the bar for the lightweight sportbike segment. The ZX-4RR serves riders looking to tap into that old-school lightweight superbike mystique and does so effectively, and with modern electronic rider aids. The North American tune is a repairable annoyance, and fully adjustable suspension would have been appreciated. But those gripes fall by the wayside when you’ve got a wildly entertaining I4 screamer that will make a rider feel drunk with power, and, thankfully, a quick-footed chassis to wrangle it into submission. In the end, that’s exactly what the ZX-4RR is all about.
RIDING STYLE
- Helmet: Arai Corsair-X
- Suit: Alpinestars GP Plus V4
- Airbag: Alpinestars Tech-Air 5
- Baselayer: VNM Sport compression top and pant
- Gloves: Alpinestars GP Tech V2
- Boots: Alpinestars SuperTech R
2023 Kawasaki Ninja ZX-4RR Specs
ENGINE
- Type: Inline-4
- Displacement: 399cc
- Bore x stroke: 57.0 x 39.2mm
- Maximum torque: 26.5 ft-lbs @ 11,000 rpm
- Redline: 15,000+ rpm
- Compression ratio: 12.6:1
- Valvetrain: DOHC; 4 vpc
- Fueling: EFI w/ four 34mm throttle bodies
- Cooling: Liquid
- Transmission: 6-speed w/ quickshifter and Positive Neutral Finder
- Clutch: Web multiplate w/ assist and slipper functions
- Final drive: Sealed chain
CHASSIS
- Frame: Steel trellis w/ steel swingarm
- Front suspension; travel: Spring-preload adjustable Showa SFF-BP 37mm inverted fork; 4.7 inches
- Rear suspension: Linkage-assisted, fully adjustable, cantilevered Showa BFRC Lite piggyback-reservoir shock; 4.9 inches
- Tires: Dunlop Sportmax GPR-300
- Front tire: 120/70 x 17
- Rear tire: 160/60 x 17
- Front brake: 290mm semi-floating petal disc w/ radially mounted 4-piston monobloc calipers
- Rear brake: 290mm petal disc w/ single-piston caliper
- ABS: Standard
DIMENSIONS and CAPACITIES
- Wheelbase: 54.3 inches
- Rake: 23.5 degrees
- Trail: 3.8 inches
- Seat height: 31.5 inches
- Fuel tank capacity: 4.0 gallons
- Curb weight: 416 pounds
- Color: Lime Green/Ebony
2023 Kawasaki Ninja ZX-4RR Price: $9699 MSRP
2023 Kawasaki ZX-4RR Review Photo Gallery
