I pose a question to you, name me one of the best sounding engines ever. Surely on the list goes the fabulous Wankel engine, made famous in the Mazda RX-7. If you have ever owned a Wankel or even heard one when unleashing its fury, you’ll understand why it makes the list. Famed for having huge power to weight ratio advantages and such a distinctive roar.
The Wankel engine did make it to motorcycles when Norton took the RCW588 race project in the ’80s and ’90s combined with the NRV588 when the previous Norton ownership took over. The man behind the Norton rotaries, Brian Crighton, continued developing, starting with the CR700P in 2013 and now the CR700W.
The development process is easy to see, it retains the handbuilt Spondon frame chassis, and the homage to the Wankel engine is evident with the rotor shape under-seat exhaust and air intake vents. The Wankel engine takes up much less space, the belly pan is curved, like the 2009 Norton NRV588.
Wankel engines have always been great at making power in a low cc package. A Wankel fires three times in one complete revolution, whereas a conventional four-stroke piston engine requires two full revolutions, and a two-stroke requires one. The engine built by Rotron, who make aircraft, drone and marine engines, makes 22hp from a 690cc twin-rotor engine. The rev limit of 10,500rpm should also excite! Weighing 24kg for the engine alone and 43kg when including the Nova Transmissions six-speed gearbox.
The downside to rotary engines has always been reliability. Apex and tip seals wear, which causes low compression issues, and makes them hard to start. Many RX7/RX8 owners premix two-stroke oil into the fuel to try and reduce wear of the tips, but Rotron and Crighton’s new low friction two-piece silicone nitride seals claim to eliminate wear.
Added development see the main eccentric shaft manufactured from a cryogenically established EN36 steel, and completely new is a spark-eroded internal cooling channel providing liquid coolant to the main rotor bearing journals, via a shaft driven coolant pump. New titanium and Inconel exhaust ejector system creates a vacuum through the rotor housings accelerating airflow and uses zero moving parts.
The CR700W is a unique motorcycling masterpiece and a true work of art, born out of Brian’s passion and genius when it comes to creating extraordinary engines and race bikes. It is more powerful per cc than any other normally aspirated engine in the world, with a greater power-to-weight ratio than the Aprilia RSV4, or even the supercharged Kawasaki H2R. The performance speaks for itself, yet despite the numbers it is far from a highly-stressed racing engine that needs rebuilding after every race weekend, and instead, thanks to its low-revving design, ultra-low friction materials and unique internal geometry, it is resoundingly robust and reliable, and will run a full season before requiring internal inspection. There are few machines as exclusive, with performance and uniqueness to match.Alex Head – Rotron Power CEO
So it’s got a wicked engine making 220hp, an excellent developed chassis, making the combined total package weight 130kg’s dry. Dymag carbon wheels reduce unsprung mass, Brembo brakes, and either Ohlins or Biturbo suspension pack the premium parts onto the track bike, giving ultimate performance.
All of this does not come cheap, the Crighton CR700W has a price tag of £85,000 each, and there will only be 25 examples made, hand-built by the head of Crighton, Brian, aged 73, at the Rotron power facility in Wiltshire. The website does list a road registered option also available. Hopefully, some get road registered!
In so many ways the CR700W is the culmination of my career’s achievements. Developed with my excellent lead engineer, Shamoon Qurashi, it encapsulates the absolute best of my engineering wisdom. And I believe the result is the ultimate track and racing motorcycle.Brian Crighton
When you look at the specs and crunch some numbers, the CR700W should be a rocketship; the engine makes more torque than an RSV4 in a smooth manner that is vibration-free thanks to the smoothness of the rotary engine. With a power to weight ratio so 1.68 hp per kg, more than a WSBK (around 1.5hp/kg) with MotoGP machinery at around 1.65-1.8hp/kg.
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