The Ninja 400 has the edge over the RC 390

Kawasaki’s Ninja 400 and KTMs RC 390 make for a great comparison.

Both motorcycles are entry-level sports bikes that share similar engine capacities, power, and weight. The main differentiator is that the Kawasaki Ninja 400 is a two-cylinder engine while the KTM RC 390 makes do with one cylinder.

The other noticeable difference is that the KTM RC 390 also gives away 26 cc in engine capacity.

In the class of sub 500 cc sports motorcycles, along with Honda’s CBR500R both the Ninja 400 and RC 390 lead the class in terms of engine performance and straight-line speed.

— Ninja 400 — KTM RC 390

Ninja 400 & RC 390 Dyno curve compared

Kawasaki’s Ninja 400 is powered by a 399 cc liquid-cooled 4-stroke 8-valve DOHC parallel twin. Kawasaki claims 49 horsepower at 10,000 rpm and a torque of 28ft/lb produced at 9000 rpm.

Claimed output can vary depending on the market but a couple of horsepower.

KTM’s RC 390 concedes some capacity to the Ninja 400. It’s powered by a compact 373 cc single-cylinder engine that produces a claimed 43 horsepower at 9000 rpm and a little over 27 ft/lb that kicks in at 7000 rpm.

On paper, the Kawasaki  Ninja 400 engine definitely has the edge of producing higher claimed peak power and torque figures than the KTM RC 390.

The peak power and torque advantage that the Ninja 400 has on paper is predominately due to its 26 cc engine capacity advantage.

This may not sound like a lot but when talking about small engines even a slight capacity advantage can make a huge difference.

On the dyno, things get a little closer…

The KTM RC 390 produces very a peak of 43 horsepower @ 8600 rpm which exceeds the crank figure claims of the KTM. Very impressive.

Typically motorcycles produce less power and torque at the wheels compared to the crank claims from the manufacturer.  This is because there is a proportion of power that is lost as it is transmitted from the crank to the wheels. 

The losses typically equate to around 10-12% but vary.  For example, a light chain or lighter wheels and tyres can mean less power lost as it’s transmitted from the engine to the rear wheel.  

The KTM RC 390 also produces the same 27 ft/lb peak torque at the rear wheels that  KTM claims, and bang-on 7000 rpm.

The RC 390’s power and torque curve is not typical of a single-cylinder motorcycle and has a closer resemblance to a larger capacity to a short-stroke L twin-cylinder motorcycle. 

This likely has much to do with the RC 390s short-stroke and high-revving design. 

The KTM RC390 makes decent torque right off the bottom though being a single-cylinder engine it’s a little ‘chuggy’ and lumpy from 2500 rpm but smoothens up from 3000 rpm where it produces a flat torque curve.

It’s from around 5000 rpm in the range where the KTM RC 390 delivers the first of two kicks in power and torque. 

From 5500 rpm power and torque flatten off again with another noticeable kick at 6500 rpm with a peak power of 43 horsepower arriving at 8600 rpm. 

The RC 390 continues to make power which gradually falls away and then aggressively drops as it approaches its rpm limiter.

Small engines tend to have flatter power and torque curves, with any kick or surge barely noticed as you roll on the throttle but the RC 390 really has a Jeckle and Hyde type delivery with two distinctive and noticeable kicks in the powerband.

For a small engine with modest power, the KTM RC 390 engine feels more powerful and is genuinely exciting and enjoyable to thrash and loves to be revved which is very uncharacteristic of a single-cylinder engine outside of competition motocross engines

For Kawasaki’s Ninja 400, at the rear wheel, we see a potent 44 horsepower delivered at 10,000 rpm. Peak torque is 25 ft/lb at 8500 rpm.  

The Ninja 400s power delivery resembles a four-cylinder motorcycle as opposed to a two-cylinder.  Its power and torque curve are extremely wide and impressively the Ninja 400 produces close to 90% of its peak torque from a little over 4000 rpm.

There are a few peaks and troughs throughout the range but on the road, the power and torque delivery is very linear, progressive, and a lot smoother than the KTM RC 390.

While the Ninja 400 produces its peak power at 10,000 rpm,  it holds onto that power extremely well for a two-cylinder motorcycle and all the way to 12,000 rpm plus which provides plenty of useability.

If we compare both power and torque curves The Ninja 400 produces more peak power but gives away a little peak torque.

Throughout the rpm range, the Ninja 400 produces more power and torque and also holds onto its power and torque for longer.  It’s only between 6500 and 7500 rpm that the RC 390 has an advantage. 

Everywhere else the Kawasaki Ninja 400 engine is stronger!

Even at the bottom end the Kawasaki Ninja 400 produces substantially more torque which is impressive for a two-cylinder high-revving engine that is up against a very competent and highly tuned single-cylinder engine that ultimately revs lower.

To be fair to the KTM 390 its engine does give away 26 cc, though among small-capacity engines this is quite a substantial advantage to the Kawasaki Ninja 400. 

I am not sure that if their engine capacities were the same, the KTM RC 390 would produce more torque than the Kawasaki Ninja 400  below 5500 rpm.

My best guess would be that they would produce similar torque though the RC 390 would be much more dominant in the upper midrange and would make more power too.

Looking at the engine outputs alone, the Kawasaki Ninja 400 definitely has the advantage as it produces more peak power and it produces more power and torque on average throughout the rpm range. 

The KTM RC 390 is m a more explosive engine while the Ninja 400 is more linear and predictable and delivers its performance longer and wider.

— Ninja 400 — KTM RC 390

In gear thrust curve

When actually using these engines as intended things look a little different.

The KTM RC 390  actually claws back some of the advantages that the Ninja 400 has in terms of engine performance on the dyno.

Both motorcycles are a similar weight with the KTM RC 390 coming in slightly lighter.

Even if only a few kilograms, all other things being equal this does help close the gap with in-gear and outright acceleration in favour of the KTM RC 390. 

The main factor though is KTMs choice of gearing. From first gear, all the way to fifth gear the KTM RC 390 has lower gearing than the Kawasaki Ninja 400.

Ninja 400 vs RC 390 speeds in each gear

In the first three gears at almost any speed if side by side with the Kawasaki Ninja 400, the KTM RC 390 is more accelerative as it produces more thrust so punches a little harder when cracking the throttle.

There are only a couple of points early on in either of the first three gears where the Ninja 400 has the edge, and that’s between 16-17 mph in first gear,  22-25 mph in second gear, and 25 mph to 32 mph in third gear.  

That slight advantage that the Kawasaki Ninja 400 has in the first three gears at those specific speeds is very short-lived, with the KTM RC 390 dominating for 80 plus percent of the speed range in each of the first three gears

Though not to miss, both thrust curves fall off rapidly right at the higher end of their speed range for the KTM RC 390. 

The Ninja 400 right at the top of the speed range of each gear produces more acceleration and thrust than the KTM RC 390 as it falls off less rapidly as also seen on the Dyno with the Ninja 400 holding onto its torque for longer.

As we get into fourth gear and upward the advantage to the KTM RC 390 starts to diminish with every up change. 

If we look at sixth gear for example the Kawasaki Ninja 400 is dominant everywhere except at around 77 mph which is the speed at which the KTM RC 390 produces peak torque in sixth gear. 

The Ninja 400 is also on average stronger in fourth and fifth gear for most of the speed range ( in those gears) and only conceding where the KTM produces its peak torque.

How the above translates on the road is that the KTM RC 390 at lower speeds and in the first three gears will be more explosive and accelerative than the Ninja 400 and will pull a few bike lengths upon the initial roll of the throttle.

This will be true at least until the KTM RC 390 has to change up, which it needs to as it is lower geared and thus has lower peak speeds in each gear while the Kawasaki Ninja 400 would still be charging in a gear lower.

This is because the Kawasaki 400 on the other hand can hold onto each gear a little due to longer gearing and more rpm r and as a result close in on the KTM RC 390 eventually.

As we get into the higher gears the ( 4th,5th, 6th) Kawasaki Ninja 400 will accelerate harder at almost any speed gear-for-gear and especially so above 8000 rpm in those gears.

If you’re riding the KTM and want to maximize chances against the Ninja 400, then you’d definitely want to be riding that peak torque, which is a little over 56 mph in fourth, just under 66 mph in fifth, and around 75 in sixth gear. 

In the last three gears, If rolling on from where the KTM is strongest, it would jump ahead slightly, maybe a wheel length or two, and then both would sit even for a while with the Kawasaki Ninja 400 eventually overtaking and slowly walking away.

Due to the Kawasaki Ninja 400 having longer gearing in the first five gears, and also revving higher than the KTM RC 390, there are many situations where the Kawasaki Ninja 400 can afford to be running one gear lower than the KTM RC 390 to accelerate from the same speed.

For example, the Kawasaki Ninja 400 could use second gear to accelerate from 40 mph to 60 mph, while the KTM RC 390 would really need to be using third gear.

The Kawasaki Ninja 400 Produces much for thrust and acceleration in second gear from that speed versus the KTM RC 390 using third gear which is clearly demonstrated in the thrust curve above.

The KTM RC 390 could use second gear, but it would be way up in the revs and would need to change into third almost instantly after cracking the throttle as it would run out of rpm in a second very quickly.

It would also lose time with the gear change.

The KTM RC 390 fairs better when the speeds are lower, and the gears used are lower while also driving gears from low-speed or low rpm. 

As the speed gets up and the gears used become higher  (4th,5th,6th) the Kawasaki Ninja 400 is stronger almost anywhere.

Ultimately in the most competitive riding situations, the Kawasaki Ninja 400s engine would come out top and would require less work with the gearbox. It’s just overall a more flexible engine more of the time. 

— Ninja 400 — KTM RC 390

Ninja 400 vs RC390 acceleration through the gears

With similar power and weight, it was always going to be close between these two machines.

They are close enough that one rider being larger and heavier than the other could be the deciding factor in a straight-line sprint.

Equally, one rider lacking skill compared to the other will skew any results in either direction.

With under 400 cc in engine capacity and 40 odd horsepower, it would be easy to assume and write off these machines as not that quick.

Being lightweight and geared optimally for the power that these machines produce means that they actually go pretty well below 100 mph.

You have to work those engines and gearboxes and be very precise with the launch and gear changes, as well as getting your tuck down and like a Moto3 racer to get the most out of them.

If you compare both from a dig it is the Kawasaki Ninja 400 that has the slight edge from 0-60 mph but the KTM RC 390 does get the initial jump and has the edge from 0-30 mph.

Both machines are relatively easy to launch compared to larger more powerful machines but both will still wheelie in first gear.

The KTM RC 390 is more wheelie prone in first gear as there is more peak thrust available. This does make it a little harder than the Kawasaki Ninja 400 to launch when chasing good ETs. 

The sprint from 0-60 mph is very close!

The Ninja 400 is faster from 0-60 mph

The Kawasaki Ninja 400 has a slight edge recording a time of 4.07 seconds compared to the KTM RC 390s 0-60 mph time of 4.27 seconds.

As mentioned the KTM RC 390 does get the edge initially, and this is because of its extra thrust in first gear though this can also be a bit of a hindrance as the RC 390 is more likely to lift. 

The KTM RC 390’s first gear tops out at around 35 mph but you would want to change up a little before as thurst/acceleration rapidly tails off to the point where changing up to second gear will provide more acceleration.  

The Kawasaki Ninja 400 also has low gearing but not as low as the RC 390, it also revs higher so its top speed in first gear is higher at 42 mph. 

The KTM RC 390 could be quicker to 60 mph but requires one more gear change than the Kawasaki Ninja 400. Lower gearing does not come with some disadvantages.

From 60 mph onward both machines remain pretty evenly matched with the Ninja 400 a few bike lengths ahead which it maintains.  

Things are a little more frantic on the KTM RC 390 due to the lower gear ratios and lower rpm ceiling, so gear changes are coming harder and faster.

It’s also more important where you change gear (rpm)  on the KTM RC 390 as if you hold onto a gear for too long you’ll lose time.

Generally, you should be changing gears between 9500 and no higher than 9,750 rpm to ensure the best and most consistent ETs. Taking it beyond will kill ETs significantly! 

On the Kawasaki Ninja 400, there is also an optimum rpm to change which is around 11,000 to 11,500 rpm but you can take it 12,000 rpm and beyond and lose very little whereas doing the same on the RC 390 is much more costly to ETs and overall acceleration.

It’s from 80 mph where the Ninja 400 starts to capitalize on its power advantage and starts to slowly edge away from the KTM RC 390 but it’s still very close. 

0-100 mph arrives in a very impressive 12.58 seconds for the Kawasaki Ninja 400 followed by the KTM RC 390 at 13.48 seconds and a second slower.

The KTM RC 390 does have an inconvenient gear change that hurts its 0-100 mph time as it can’t quite hit 100 mph in fifth gear, while the Ninja 400 can 100 mph using fourth gear if you take the rpm close to the limiter.

The quarter-mile time is achieved a fraction after hitting 100 mph for the Kawasaki Ninja 400 at 13.02 and 101.2 mph terminal speed. 

The KTM RC 390 is a couple of bike lengths behind scoring a 13.16 seconds time hitting a 99 mph terminal speed.

It’s very close between the two at anything below 100 mph.

From 80 mph as mentioned the Ninja 400 has a slight edge but the most significant difference in acceleration between the two is from 100 mph and beyond.

The Kawasaki Ninja 400s top end is stronger for sure. 

Most of this is because of gearing and the extra power of the Kawasaki Ninja 400 at higher rpm.

Also to note is that the Ninja 400 is a roomier motorcycle and provides better protection from the elements. The KTM RC 390 is smaller and maybe more slippery but the rider becomes more of a hindrance to top-end acceleration and ultimately top speed.

The Ninja 400 has a 6 mph higher top speed than the RC 390 

Rider size and weight make a much bigger impact on the performance of lower-powered motorcycles. 

Stretch both machines to their max and the Kawasaki Ninja 400 comes out top quite easily with around a 6 mph advantage scoring a top speed of 118.3 mph compared to the KTM RC 390’s top speed of 112.5 mph.

The Kawasaki Ninja 400 has more to go, just not for us…. as

I have seen many examples exceed 120 mph. The KTM RC 390 on the other hand would need longer gear ratios to go any higher if the power could push the gear. 

At its 112 mph top speed the rpm is right at the limiter and just sits there with no more to come.

In the end, both are very closely matched din terms of performance.

If you ride in town a lot then the KTM RC 390 will be more punchy and provide better and more accessible acceleration more of the time.  But you will be tapping that gearbox more often due to the limited speed range in each gear.

In town, you will be able to be a little lazier with the Kawasaki Ninja 400s gearbox as it still provides more than enough poke but as gears have a wider speed range you will change gears less often.

Once out of town the Kawasaki Ninja 400 will make a little more sense and prove a little bit more performance on faster roads compared to the KTM RC 390 but it’s still very close between the two.