Home » The Kawasaki Ninja ZX-4RR KRT Edition Has A Tiny, Angry 400cc Four-Cylinder Engine, And We Need It

The Kawasaki Ninja ZX-4RR KRT Edition Has A Tiny, Angry 400cc Four-Cylinder Engine, And We Need It

Kawasaki Ninja Zx-4rr Krt Edition Topshot

Smaller-displacement four-cylinder motorcycles. For decades now, they’ve basically been an extinct species. Too costly, too polluting, pulling too much out of too little displacement. I never expected a big manufacturer to make another one, but Kawasaki is stepping back into the ring with a new bike powered by a tiny four-banger. It’s called the Ninja ZX-4RR KRT Edition, and it looks amazing on paper.


What we have here is a 399cc four-cylinder sportbike, the stuff of Japanese motorcycle legend. Bikes like the Yamaha FZR400 drew praise for sophistication, only to be stamped out by cheaper two-cylinder bikes.

Indeed, the Ninja ZX-4RR KRT Edition has a similar cost conundrum. At $10,434 including freight fees, it commands a $4,400 premium over a base two-cylinder Ninja 400. Take a closer look though, and that price difference can almost be justified.

Kawasaki Ninja Zx-4rr Krt Edition Guts

First, there’s the crown jewel of the Ninja ZX-4RR KRT Edition: its 399cc four-cylinder 16-valve engine. Featuring massively oversquare combustion chambers, this motor breathes through four individual 34mm throttle bodies and spins to a proper 16,000 rpm. According to Cycle World, the European press kit quotes 80 horsepower thanks to the use of a ram air intake. On a bike that weighs 415 pounds, that should be enough to get the hairs on the back of your neck standing straight up.

Kawasaki Ninja Zx 4rr Krt Edition Rear Close

Six forward ratios with a quickshifter and a slipper clutch are on hand to let you make the best use of all that fury, while Kawasaki’s multi-mode traction control should keep the 160/60ZR17 Dunlop Sportmax GPR-300 rear tire from vaporizing. As far as other rider aids go, ABS comes standard and riders can choose between low and full power modes.

Kawasaki Ninja Zx-4rr Uncovered

As for the chassis, the Ninja ZX-4RR KRT Edition gets a trellis frame and Showa dampers front and rear. An inverted fork up front and an adjustable horizontal rear link should offer good travel and control, while a four-piston front caliper and a single-piston rear caliper clamping down on a 290mm disc and a 220mm disc respectively, should you wish to bring the fun to an end.

Ninja Zx-4rr Pov

The KRT Edition bit of the Ninja ZX-4RR KRT Edition name means that this angry little four-banger comes drenched in Kawasaki green, and it gets a wicked set of red and black graphics that give the whole bike a mad 2000s vibe. The visual treatment is as loud as a can of watermelon Four Loko and I reckon it’s better proportioned than a similar livery on the ZX6-R KRT Edition.

Ninja Zx-4rr Rear

Remember, four-bangers this small are pretty rare nowadays. As MotoFomo listed a while back, some other examples include the Honda CBR250RR, which had a 250cc four, or the Kawasaki ZX-2R, which boasted the same size motor as well. Both are from the 1990s. Heck, you’re vastly more likely to find a bike engine 400cc or under with just one cylinder, or maybe two. But four? That’s what makes this thing so wild.

So, is the Kawasaki Ninja ZX-4RR KRT Edition worth the $10,434 price tag? Well, it depends on what you want. If you just want a cheap, fun, 400cc bike, you’re probably better off with something like a Ninja 400. However, if you yearned for forbidden fruit like the Honda CBR400RR, this new Ninja is shaping up to be a proper cult classic. I’m properly stoked that this bike exists and can’t wait to hear it scream.

(Photo credits: Kawasaki)

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37 Responses

  1. basically it is track bike homologomation. I doubt many outside of track racers looking for a fun weekend representation of what they ride on the track will ever look twice at this at that price.

  2. It’s got all the same neat shit as the zx6r for $1000 less. I wouldn’t be surprised to find that the price gap between manufacturing the 2 bikes is actually even smaller than that. I understand why it costs what it does, but also understand that it will be a hard sell for a lot people.

    1. Depending where you are, unless these get a bad rep., they should be considerably cheaper to insure than a typical 600 super sport. That might be a consideration with younger riders especially.

    1. The 400 Four was cool looking, however hindsight is always Kodachrome. The CB400F made a claimed 37 horsepower at the crank, it would manage 14 1/2 second quarter miles and could barely make it past the “ton” on a long straight road.

      A modern garden variety Ninja 400 twin would eat it alive.

      Really the Honda other than being an inline 4 is no comparison to this modern bike. That is good and bad though as you would probably be a lot more comfortable after 100 miles on the Honda than the ZX-4RR.

  3. You know what we need that engine in? A 3-wheeled one-seater microcar based upon a Shell Eco Marathon racer, with the components of proper specification to handle the output. THAT would be pretty damned crazy. Cheap to build, enclosed, extremely fuel efficient(possibly exceeding 300 mpg), and it would haul some ass just as the motorcycle does…

  4. Man, there’s just something about a small-displacement engine that punches above its weight that is like catnip for me. All four cylinders together are barely bigger than a soda can, but it makes 80 hp! And it revs to over 9,000 16,000 rpm! It must sound like an absolutely FURIOUS hamster. With a megaphone.

    I love it.

  5. It’s quite expensive, but, it’s also probably the last time we can buy a bike like this before emissions rules kill them off forever.
    Kudos to Kawasaki for making this bike, not many manufacturers are willing to spend money to develop new bikes like this.

  6. It makes a lot of sense, the ZX25RR sibling would be seen as too small for the North American market, whereas the similar ZX4RR will likely get a foot hold.
    If I was younger this would be really appealing, as I’m an old guy I can stifle that inner voice, which is good. )-;
    What a great little twisty road and track day weapon.
    IMHO the price is not that bad either.

  7. My first bike was a Kawasaki ZXR400. This is new bike is like that, but with 15 more bhp and 20 fewer whatever-units-we-use-to-measure-prettiness. Back then I test rode all the race-rep 400s: VFR, CBR, FZR and the GSX-R. So many revs. I wish I’d tested the 250s too, just to experience 20,000rpm.

    Last year I rebuilt a Honda RVF400. It’s the peak of 90’s 400s. Getting used to the lack of torque has been fun. The engine basically does nothing under 8000rpm, so you end up thrashing it everywhere, but without ending up accidentally doing going-to-jail speeds (I’ve found myself doing 140mph without realising it on big bikes). I did more miles on it in the first week than I’d put on my ZX7R in the previous year.

    Fun is way more important than speed.

  8. I like revyy little bikes but this is a bad deal.
    The ZX6r has the same redline, a massive increase in power, costs only a couple of hundred bucks more and adds only 7kg.
    If the 400 was genuinely light i might bite,but not as it is

  9. My Honda CB-1 is the one bike I’ve owned I wish I had never sold. Put the most grins-per-mile of anything I’ve had since. There’s something about pinning the throttle, spinning up to 14k RPM, banging off one then two shifts tucked in… And then looking down at the speedo to realize you’re not even in “go directly to jail” speed territory yet. Driving a slow anything fast is way more fun that driving a fast anything slow! This new bike would be a hoot to drive if I were still at my 00’s body weight!

  10. Years ago bought an FZR400. The one and only time I bought a new bike. Was fantastic. Had to buy it new as used were few and far between. Plenty of FZR600s around. As I recall it had 50HP to the 600s 70. Weighed 350lbs to the 600s 400lbs. That 50lbs made a world of difference to me. To the market though the FZR600 was much more popular. Most likely be the same this time.

  11. A million years ago when small displacement 4 cylinders were common, I lived in Japan and did a lot of cafe racing on the Hakone Skyline, etc. Most of the cafe bikes of the day were either 250’s or 400’s: the reason being the difficulty of getting a ‘heavy’ motorcycle license. Not only is the test much more difficult but (in those days at least) you had to prove you could pick up your bike lying on its side – a pretty big ask for most comparatively small Japanese guys. Add this to the taxes on heavy bikes, and well 400 cc was the sweet spot for most guys.

    So, the market for this bike isn’t really the U.S. – it’s Japan. People in Japan will pay for bike bike power in a 400 cc because that’s the only practical way to get it. That may also be true in Europe, but I don’t know. Here in the U.S. it’s easy to just buy a bigger displacement bike.

    I rode and raced cafe-raced against some of the hot 400 4’s of the day and they were a LOT of work to ride fast. The reason is that the power band that generates that kind of number is very high and very narrow on a quick revving engine. You have to keep the bike on the boil all the time or bog. So you come hot as you can into a tight turn and grab a big handful of brake, lean the bike over, pull in the clutch, go down two (or three) gears, grab a big handful of throttle and accelerate out. Fall out of the power band and the dance is on to match the rev’s to the gears cause there is almost zero torque out there, so add watching your tach to watching where you’re going and watching the other guys around you. Takes a lot of practice to get good at it.

    Me? I rode a cafe-tricked-out Yamaha XS 650 vertical twin. Tons of torque across a wide power-band. Handling was a little slow (especially compared to the 16-inch fromt wheel kids) so you had to pick your line early and your only tool was more throttle! and more lean. It was like cafe racing a steam locomotive but you could concentrate on your line while everybody else was busy shifting so it did pretty well.

    Sigh…I miss those days.

      1. My first bike was a ‘76 XS650 I bought from my dad. He had all the parts to put it back together (had been sitting for decades), so I went to work one summer in college working like a man obsessed well past midnight for several weeks to get her mechanically right. I then had everything rechromed and repainted. Man, that bike was sweet! I only got rid of her after getting sick of my wife complaining about me having 2 bikes (other was a BMW K1300GT). Now, I’m down to a 1980 BMW R100. Still miss my Yamaha..sigh..

  12. 100cc per cylinder, and 4 valves per cylinder.
    Let’s assume the cylinder bore is 50mm.
    Let’s assume the nose of the spark plug is centered in the bore and that it’s 14mm diameter.
    Allowing room for valve seats, etc… the valves are… 14mm in diameter?

    TWEEE! How CUTE!

  13. Light hypo bikes are a blast for everything except touring. For a few years in the early 80s I owned a Honda 350 Four. Was ok, didn’t love it. Sold it and bought a ‘68 Triumph Bonnieville .

    Hindsight- if the Honda handled like the Triumph, it would have been sweet. And if the Bonnie likewise, the same.

    The Yamaha 650 Seca solved both issues.

  14. This engine with a very short racecar-like gear would be super fun in a 1500lb Insight with a manual.

    I drool thinking of a 5.2 to 1 final drive to have enough torque to move a car and quickly get the revs up. Stock was a 997 cc 3 cylinder with 68hp, this engine could use a better gear to have some torque due to the sky high revs.


    1. I was thinking 3-wheeled enclosed monocoque plastic-reinforced glass fiber and aluminum honeycomb microcar with the form factor and drag of a velomobile, weighing somewhere around 300 lbs.

      210+ mph top speed and 25+ mpg at top speed would be theoretically doable. Many hundreds of mpg at legal speeds for commuting to work. You could hoon the shit out of it and save lots of money over using a penalty box econocar in a boring/conservative manner.

        1. I once read of someone who took a stock 1st generation Insight and turbocharged the engine. 0-60 mph acceleration time dropped to 7 seconds, but the car also could still sip fuel if you kept your foot out of it and could still be competently hypermiled. Driving like a total jackass hoon, the owner got 30 mpg, but driven normally it retained stock Insight mpg figures. Consider in those lead-footed hooning conditions your average new non-hybrid 2023 4-cylinder gasoline-ICE sedan would struggle to break 15 mpg, even though it could get 35 mpg driven sanely.

          I know another individual who took a 1st gen manual Insight, gutted the electric drive system and battery, and K-swapped it. 0-60 mph in under 6 seconds, around 35 mpg city, 50 mpg highway driven normally. That engine has enough power that with optimized gearing, this thing could theoretically be hitting around 190 mph… although this example probably doesn’t. The owner never told me its top speed.

  15. I do love the idea of this bike for sure, but 415 pounds??? That’s crazy, right? It’s only 10 lb lighter than the ZX-6R which makes 54 more ponies. Have I just not been paying enough attention to what small displacement bikes now weigh?

  16. 4 cylinder bikes are fun. I briefly owned an R6. At low RPM’s it pulls like a really powerful sports sedan, at high RPM’s it was a rocket. I bought it to clean up, fix and sell – would have kept it longer but it was so monumentally uncomfortable that I let it go. I’m a road cyclist so I’m used to an aggressive forward position but I couldn’t ride it for more than 45 minutes before wanting to get off. The engine heat, the mirrors buzzing, my wrists. Good fun while I had it though.

    1. I started on a Ninja 500, graduated to a ZX-6R, and then moved up to a CBR-1000RR over a span of 12 years of riding. It’s been seven years almost since I hung up my helmet for the last time and I still miss it. I rode 1500 miles the first week I had my 1000RR back in 2012. Those were the days.

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