Adamchildchad Forties, 5'7, has been professionally bike testing for 20-years and has attended more than 350 bike launches and covered over a million road test miles. International road racer, with race wins at Oliver's Mount, podiums in NZ and two top ten TT finishes. Chad is just as happy off-road or on a classic bike.
Back in the late 1980s and early 1990s there was a brief moment when 400cc four-cylinder sports bikes were the peak of motorcycle engineering. Honda’s NC30, NC35 and CBR400RR, Kawasaki’s ZXR400, Suzuki’s GSX-R400 and Yamaha’s FZR400R combined superbike chassis with screaming engines that exaggerated every Japanese cliché about miniaturisation. They were full-blown superbikes in all-but the size of their bores and, on the road, they were bloody brilliant.
Japanese licensing laws favoured 400cc bikes sparking an arms race to build the most special, most sporty, trickest machines. Most weren’t officially imported to the UK but they arrived anyway via independent importers who realised the value to new riders of a usable-but-brillliant sports bike. A whole generation of riders in the 90s learned how to ride quickly and safely on sports 400s. They were astonishing machines and many of us still have a soft spot for a balls-out 400 sportster.
And now, Kawasaki have brought the class back with the ZX-4RR.
With a claimed 75hp on tap (in this RR spec in Europe – other markets have restrictions) the Kawasaki’s output demolishes all those 1990s forebears but with modern fuel-injection remains flexible enough to let you wring its neck on the back roads and potter through the villages at 30mph without any mechanical grumbles.
Pros & Cons
The sound of four tiny pistons at 16,000rpm
Sufficient but not excess power
Quality suspension
Fast when you want it, docile in town
Small-but-roomy, light and agile
Good looking and well-equipped
Roomy for a small bike, not comically small like the old ZXR400
Good looking and desirable
Lack of damping adjustment on the front suspension
Steel frame lacks the family feel of bigger Ninja’s alloy units
Noisy getaways, not exactly discreet
Surprisingly heavy on fuel (or not surprising, given the behaviour it encourages)
Kawasaki ZX-4RR Launch Review (on track)
Price: £8,699 | Power: 76.4bhp | Weight: 188kg
Kawasaki ZX-4RR tested on track by Adam 'Chad' Child at Calafat in Spain, but what does our regular road tester and part-time racer think of this 400c screamer?
The mini-Ninja’s £8699 is almost £2000 more than Kawasaki’s twin-cylinder Ninja 400 and £1200 more than the also twin-cylinder Ninja 650. It makes almost twice the power of the Ninja 400 and ten bhp more than the Ninja 650. But it’s also £2200 less than the 120bhp ZX-6R and so, probably just about perfect for where it sits. PCP prices with a £1500 deposit are £124 a month.
Yamaha’s R7 (£8910) makes similar power to the ZX-4RR with considerably more torque and almost the same commitment to sportiness. Aprilia’s RS660 is more expensive (£9650) but more powerful too and in some eyes, the current market leader for middleweight sports bikes. Suzuki’s recently announced GSX-8R makes a little more power, a lot more torque but, like the Aprilia and Yamaha is a parallel twin engine with a completely different character.
Kawasaki’s four-cylinder maverick is a breath of fresh air. Up-and-down quick shifter is superb and always busy
The ZX-4RR’s four-cylinder engine is derived, like the rest of the bike, from the 250cc ZX-25R that’s been around since 2020. The extra capacity comes from increasing the bore from 50mm to 57mm and the stroke from 31.8mm to 39.1mm. Compression ratio is 12.3:1 which gives a claimed power figure of 57kW (76.4hp), rising to 59kW (79.1hp) when ram air effect is added at speed.
There are different specs and power outputs in different markets. Europe gets the full power versions, but the USA, for instance, has a restricted 42kW (56.3hp) ZX-4RR and in Australia the power is pegged at 55kW (73.8hp).
There are four riding modes – Sport, Road, Rain and Rider-adjustable – each altering the bike’s power map and traction control settings. The ZX-4RR also gets an up/down quick shifter as standard and given how much you use the gears to keep that engine on the boil it’s a very worthwhile addition.
Peak power arrives at 14,5000rpm while peak torque, 39Nm/28.8ftlb, is only just behind it at 13,000rpm. The power figure is impressive for a small-capacity Euro5 bike (small multi-cylinder bikes have serious problems passing Euro-5 because high rpm creates lots of NOx), and almost 30 percent up on the old ZXR400, which had no emissions equipment and even when tuned for racing would only make 75-80hp.
Kawasaki’s engineers have juggled the torque and revs calculation smartly. The engine makes very little torque (like the previous 400s and most of the 1990s two stroke 250s if you’re interested) but has enough rpm to make the extra power.
So, you need to keep the ZX-4RR on full volume for most of the time. Thankfully, the super-smooth up-and-down quick-shifter makes this easy. The 399cc, 16-valve motor revs quickly, and is surprisingly forgiving if you give it too much throttle in too high a gear. The sweet spot is between 8-15,000rpm. That’s a wide powerband and even banging into the rev limiter at 16,000rpm doesn’t feel intrusive.
The gear change is slick but finding neutral at a standstill takes more finesse than most bikes. You soon get the hang of it, but setting off from rest is a noisy affair at first as you misjudge how quickly it revs and open the throttle too far while releasing the clutch, setting curtains twitching and muttered grumbles about teenage hooligans etc. On the road the secret is to almost release the clutch fully before applying any throttle to get the bike rolling and then add the power smoothly. Otherwise you get a lot of noise and not enough forward motion to impress the onlookers who are all now staring at you.
Riding position is surprisingly roomy. Oh, and it goes as well as it looks
This is not a slow bike by any standards, but it very rarely feels like a fast one either. Until you look down at the speedo and realise just how rapidly you are moving. It’s all relative of course. If you’ve just traded-up from a 125, the ZX-4RR will feel like the fastest thing on earth. If you traded down from a bigger bike (and there are very good reasons why you might), it’ll take a few hundred miles to get used to the Kawasaki’s power delivery.
It reminds me of a 1990s two-stroke 250 (where powervalves and smart ignitions smoothed out the powerbands) in that the power builds gently, but relentlessly without ever feeling power-ful. Ride it without looking at the tacho and the engine gravitates towards 8000rpm (which is also where 80mph in top gear is found). This is where you’ll find a slight step in power – the place you need to be for overtaking dawdling cars on B-roads - from where it flies through to 14,000rpm and the dash lights up orange before you hit the redline at 16,000rpm.
At that point you are going way, way faster than you imagined. Getting on for twice the top speed of that 125 you part-exchanged or barely any slower than the ten-year-old superbike you traded down from because it was too fast and scary.
There’s no extra power in those last 2000rpm but it makes a useful over-rev that allows you to hold onto a gear for a fraction longer instead of changing up when you can see there’s a corner approaching (and you’ll be changing down anyway in a split-second).
For a bike that doesn’t feel particularly fast, the ZX-4RR is all about the engine though. It sounds like what you’d get if Akrapovič built a vacuum cleaner. What’s really impressive is how docile, easy to use and tractable this motor is while gliding through traffic at 30mph. To build an engine so flexible, so revvy and so flipping fast that still runs regular E10 fuel and has a four-year (yes, really) warranty is something to be applauded. Talking of fuel, the price to pay for a bike that shares much with a 90s two-stroke is that you’ll be lucky to top 45mpg riding it as intended. Compare that to a Yamaha R7 that goes just as quick and does at least ten more miles per gallon or even a Honda Fireblade that makes three times the horsepower while using the same amount of fuel. A mix of motorway, town and backroad riding raised that to an average over the whole test of 49mpg, so tank range will be around 165 miles to empty and around 135 miles till the light comes on.
The Kawasaki is more comfortable to ride than a Fireblade or an R7. The riding position is sporty (low bars, high, rearset footpegs) but roomy too. I was surprised how not-uncomfortable it is making it a bike you could genuinely have as a daily rider and Sunday toy.
Our test in early November was mostly on cold, wet, leaf-covered roads so lean angles were modest (see track test below for elbow-down opinions), but in those conditions it was re-assuring how easily and predictably the ZX-4RR steers. It turns quickly as you’d expect for a small sports bike on a 160-section rear tyre. But it is also stable, confident and able to change line to avoid a pile of soggy sycamore.
Town riding is easy (the brilliant up-and-down quick shifter really helps here), motorways too and neat touches like mirrors that fold in on a détente so they snap back into position, gives extra confidence when filtering past van mirrors through stationary traffic.
On our track test at Calafat in Spain, BikeSocial’s tester Chad was clocking 120mph at the end of the 600m straight with rpm in hand and another gear to go. His estimate in the right conditions is a top speed around 130mph, which will be no laughing matter if you have a one of these little terriers sitting behind you on a trackday.
It’s rewarding and enjoyable to trash on track. You can be reasonably aggressive with the throttle, winding it straight to the stop. You don’t have to tickle the power in the lower gears like you would on a superbike. Instead, stay tucked and keep those revs coming. Should you get a little too carried away there is three-stage traction control, which is conventional using wheel speed sensors and not lean sensitive.
We had an official accessory road-legal Akrapovič muffler fitted (£914), which added even more desirability to the package as well as a pleasing rasp.
After seven sessions in blistering Spanish temperatures our man wasn’t even slightly fatigued. That's because the ZX-4RR is so easy to hustle; it’s not intimidating, you have time to pick the right line, spot your braking markers, and get that corner just-so. You’re not rushing up to corners, scaring yourself on the brakes and then having to muscle it to the apex. The ZX-4RR flows naturally, carries its speed and then unleashes a riot of revs and wailing exhaust that make you feel like you are on lap-record pace!
As this was a track-only test I rarely allowed the revs to drop below 9000rpm, but on the cool-down lap I did play around with the mid-range. It’s not completely gutless, you can make progress, but I expect making a fast getaway from the lights is going to require several handfuls of revs – but that’s what makes it fun, isn’t it? With the TC off, wheelies are just about possible in first gear, but you have to be brutal.
Fully adjustable rear shock is superb on road and track
The steel trellis frame is based on the chassis of the ZX-25R, but with a steeper head angle and reduced trail. The wheelbase is a compact 1380mm and kerb weight with a full tank of fuel (15 litres) is 188kg. At the track test Kawasaki had swapped the road-biased Dunlop GPR300 tyres for Pirelli Diablo Rosso IIIs.
The ZX-4RR has Showa SFF-BP forks plus a Showa BFRC-lite rear shock. The forks are adjustable for preload while the rear shock adds compression and rebound damping.
Manufacturers often scrimp on suspension spec to reduce costs on lower capacity bikes but this doesn’t appear so with Kawasaki.
On the road this translates to a ride quality often missing on sub-£10k bikes. There’s a series of three bumps on one of my regular road test routes that start with a whopper and follow with two slightly lesser ones. The first bump compresses rear suspension hard and, while a quality shock regains composure in time for the other bumps a budget unit is generally still working out what just happened when it hits the rest. The ZX-4RR handled this section with ease and control – much better than any of its rivals listed above.
Braking hard with a 13-stone middle-aged bag of ambitious old bones tests the damping settings of unadjustable forks designed for a skinny 25 year-old, but without too much drama
On the track Chad reported feeling instantly at home and found a decent pace straight from the off.
“The front-end feeling was excellent, of a similar quality to the benchmark ZX-6R and ZX-10R. Kawasaki had tweaked the suspension for this track test, adding two turns of preload on the front and, while running standard preload on the rear shock, but with 1.5 turns of compression and rebound to the rear. This was obviously done for the high temperatures and grippy rubber fitted and I later added another 0.5 turns of compression and rebound damping on the rear just to cater for my weight. The changes were noticeable - another sign that Kawasaki hadn’t opted for budget suspension.
“The confidence-boosting feel from the front end encourages you to let go of the brakes and run in hot to the apex. The steering is light and direct and ZX-4RR is easy to throw around. It tracks accurately without any of the instability you might expect from a lightweight, and there’s enough room to hang off the inside and bury your knee slider in the racetrack. Even when the pegs (with hero blobs removed) start to tickle the track, you can feel the ZX-4RR giving you feedback.
“Towards the end of the session, the Pirelli rubber was struggling with the combination of high temperatures and enthusiastic rider pushing for lap times as he tried in vain to rekindle his youth. But even when the Kawa gave the odd slide, it was progressive and non-threatening.” Thanks Chad
The compact dimensions of the ZX-4RR should make it a tight fit for larger riders, but as mentioned above, the ZX-4RR is surprisingly roomy and comfy for at least a couple of hours at a time. The mirrors work well and little things like getting to the sidestand are straightforward (Honda CBR500R, we are looking at you…) The 800mm seat height is reasonably low for a sports bike too.
The view from the seat is neat: switchgear that like most Kawasaki's is relatively simple, and a clear 4.3 TFT dash which has connectivity. There are four riding modes – Sport, Road, Rain, and Rider (manual) mode, which changes the power (full or low) and KTRC traction control (levels 1 to 3 and off). In reality though with such little torque and the broad rev range, you can leave it in ‘Sport’ mode all the time and never worry about what the weather is doing. There’s an additional Circuit Mode that changes the screen to give a large lap timer and rev counter, which is ideal for track day fun and somewhat addictive.
As mentioned above, fuel economy isn’t the baby Ninja’s biggest selling point. In theory, this could be an efficient engine and it ought to be possible to see consumption in the mid-50s mpg if you need to. But you won’t because the little green devil on your shoulder will always win.
Styling-wise the ZX-4RR is very much a baby brother of the Ninja ZX-6R and ZX-10R and could easily be mistaken for a one of its bigger siblings. As much as I like the old ZXR400 I equally like the new ZX-4RR. Despite being a small capacity bike, it’s a machine you can be proud of.
2024 Kawasaki Ninja ZX-4RR brakes
Twin 290mm front discs, each with radial four-pot calipers and a 220mm disc with a single-pot caliper at the back, with ABS at both ends.
The brakes are forgiving and strong enough for some track fun, but not too sharp on the road for inexperienced riders. The brake (and clutch) lever is span adjustable, and even at a decent track pace they showed no indication of fade.
The ABS is conventional and not lean sensitive. Our track test found it a little intrusive when pushing for a fast lap but this it to be expected on an entry level sports bike.
Yamaha’s R7 could be the biggest threat to the ZX-4RR despite a very different approach and a much bigger, twin-cylinder engine. Power and weight are close, while the Yamaha has a big torque advantage.
In Kawasaki’s own showrooms, the Ninja 650 could threaten the ZX-4RR. It’s likely to be much cheaper, but also down on outright power and rather less of a track-focussed machine.
The ZX-4RR has some mighty big shoes to fill (in our heads at least, BikeSocial tester Chad rode an original ZXR400 from the 1990s recently and wasn’t overly impressed, such is the march of time and progress). Nevertheless, the new ZX-4RR picks up seamlessly from where the original let go and is also neater, faster, safer, roomier and far easier to ride.
Kawaski have been brave to produce such an unusual bike for the times – it's the only sports 400 on the market – but BikeSocial is pleased they have. It’s great fun, loves to rev, is easy to ride and forgiving, too; new sports bike riders are going to love it just as much as old sports bike riders looking to remind themselves of what flat-out really means.
Those experienced riders can tweak the suspension, just about tuck in behind the low screen and have some old-school fun. Chad rode the ZX-4RR on track all day, pretty-much flat-out every lap, used all the power and didn’t feel tired at the end. Try that on a 200bhp litre bike and you’ll be knackered by lunchtime. The small-capacity sports bike is back – thank you Kawasaki.
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MCIA Secured gives bike buyers the chance to see just how much work a manufacturer has put into making their new investment as resistant to theft as possible.
MCIA Secured gives motorcycles a rating out of five stars (three stars for bikes of 125cc or less), based on the following being fitted to a new bike as standard:
A steering lock that meets the UNECE 62 standard
An ignition immobiliser system
A vehicle marking system
An alarm system
A vehicle tracking system with subscription
The higher the star rating, the better the security, so always ask your dealer what rating your bike has and compare it to other machines on your shortlist.
