Carole Nash
Content Writer
Published: 20th March 2020
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Kawasaki has recently announced that it is bringing back the 250cc four-cylinder four-stroke sports bike, with the launch of a new Ninja ZX-25R.

The new model which is unlikely to be available in Britain, will redline at 17,000rpm – not far off the 18,000+rpm of a factory MotoGP machine.

With tightening emissions laws having seen engines generally get bigger and slower revving, we thought we would take a look some of the production motorcycles which have created headlines over the years thanks to their fantastically high spinning motors.

We’ve avoided race bikes in our feature, otherwise we’d be focussing on the high-revving multi-cylinder Grand Prix machines of the 1960s (like Honda’s fabled RC166 250 from 1966, which was reported to rev to 20,000rpm) but these screamers still all deserve a place in the history books for their epic redlines and shrieking soundtracks.

Honda NR750 (1992)

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The 1960s saw a revolution in motorcycle racing. Two-stroke engines took over from four-strokes and delivered a higher specific power output and a simplicity that made them cheaper and easier to make and tune.

Famously Honda shunned this more basic technology and responded by making more elaborate four-strokes, with multiple cylinders to allow for higher revving motors and multiple gears to overcome the inherent peakiness of the power delivery.

When rules were changed to limit the number of cylinders and gears, Honda pulled out of racing, but when they came back in 1979 they couldn’t help but try to bend the rules once more. The result was the NR500, a novel four-cylinder four-stroke designed to take on the mighty two-stroke fours.

As a general rule of thumb revs equal power and, with valvetrain to control and power only being produced once every four strokes of the piston (hence the name), the four-stroke was always at a disadvantage. The result was a disaster, slow and unreliable, and Honda quickly jumped onto the two-stroke bandwagon – albeit with a lighter three-cylinder to the four-cylinder competition.

That wasn’t the death of the NR (which stood for New Racing) project though as, in 1992, Honda revealed the super exclusive NR750 road bike.

Priced at £38,000 new, it was the most expensive bike on the market and extremely rare. The motor revved to 15,000rpm thanks to the NR’s secret weapon – it was a V8 in disguise!

Race rules stated engines were restricted to four-cylinders, so Honda gave the NR bikes four-cylinders but made them oval shaped. That essentially made it a V8, with 32 valves (eight per piston) and two conrods per piston.

The NR750’s styling famously inspired the beautiful Ducati 916 and these days NR750s are highly desirable classic motorbikes, regularly commanding premiums of over £100,000 when they come on the market.

Yamaha YZF-R6 (2006)

The 2006 Yamaha R6 is as famous for the revs it didn’t make, as the ones it did.

Launched in a blaze of publicity, the R6 was the most advanced 600cc supersport bike of the time and made a massive deal of the 17,500rpm red line.

Except it wasn’t. Yamaha’s marketing department was somewhat optimistic in its PR spin. When tuners got it onto their own dynos they found that the ECU actually capped the engine speed at 15,800rpm. It was still an impressively revvy engine, which merits a place on this list in its own right, but it cost Yamaha a fair bit of money when they were forced to compensate customers and buy back bikes from those who felt they’d been falsely advertised to.

The bike remained a real legend in a class that went into decline with the 2008 financial crash. The 2CO model, to give it its factory designation, was mildly updated to the 13S in 2008 and became the dominant machine in 600cc production bike racing. Even if it didn’t quite rev to the levels mentioned in the brochure.

Ducati Panigale V4R (2019)

Ducati’s Panigale V4R was built to race and its high rev limit of 16,500rpm is one of the reasons why it is so competitive in superbike racing.

More revs usually equate to more power because the fuel is being ignited more frequently as the piston moves up and down the barrel more quickly. Ducati’s 16,500rpm limit is significant because is a good 2,000rpm more than most competitors, giving it a power advantage over rivals.

The 16,500rpm headline figure was also a clever work around the rules. On the road going bike, the limit is a (still heady) 16,000rpm, with the extra revs only coming in sixth. With a 180mph top speed, the odds of a rider using all those revs, even on a race track, remain pretty slim.

In world superbikes, the V4R was so dominant in the opening rounds of 2019 that the race bike had its rev limit capped to 16,100rpm – not that it slowed it down much!

Honda CBR250RR MC22 (1990)

The Big H has history when it comes to making high revving screamers, and no production screamer was screamier than the CBR250RR of the early 1990s.

Although never officially sold through Honda dealers in the UK, quite a few MC22s (as the factory designation went) made it here in small numbers through grey importers.

Back in the 1980s, Japan’s strict motorcycle tests and graduated licences meant that many bikers didn’t go to the difficulty and expense in getting unrestricted licences. The result was that the domestic manufacturers developed a whole host of exotic machines for their home market, bikes based on their flagship sportsbikes but, in some ways, even more exotic.

Kawasaki brought along its ZXR250, Suzuki had a GSX-R250 and Yamaha the FZR250R (all of which could gain a place in our top five on their own right), but the CBR250RR was probably the coolest of the bunch – not just down to the extra R in the name but thanks to it’s miniature FireBlade styling and a motor that revved to, wait for it, 20,000rpm.

All were four cylinder race replicas, and those tiny pistons and the six-speed gearbox had to be worked hard to extract that claimed 45bhp and 112mph top speed (the most allowed under the licence rules).

Loads of the bigger 400cc models made it over here and they made a lot more sense in many ways, as they were less peaky and easier to ride, but these jewel like 250s are among the most interesting production motorcycles ever made.

Kawasaki Ninja ZX-25R (2020)

Few would have expected the 250cc four-cylinder class to be revived, but that hasn’t stopped Kawasaki from announcing the new Ninja ZX-25R.

In recent years, budget sports bikes have tended to be built to a price, hence the rise in machines like the Kawasaki Ninja 300 (later 400), Yamaha YZF-R3 and Honda CBR500R, which mate relatively low-tech parallel-twin motors with steel frames and basic suspension, but for 2020 Kawasaki has revived the aforementioned 250cc class with the four-cylinder ZX-25R.

There are few classes of motorcycles that we thought would be revived but just like those late 1980s 250s, the ZX-25R looks like a scaled down version of Kawasaki’s flagship superbike, in this case the ZX-10RR, and its a howling in-line four.

With a 17,500rpm redline, its not quite as revvy as the machines of 30 years ago (most likely as a result of modern emissions equipment) and just like those bikes of years gone by it looks unlikely that they’ll be officially sold in the UK, as the ZX-25R is set to be built and sold in Indonesia.