The incredible Crighton CR700P, powered by a 200bhp rotary engine, weighs just 136 kilos. No current production superbike can match its performance...
It seems we aren’t the only ones who are deeply fascinated by rotary-engined motorcycles – mainly the Norton F1 (see here, here, here and here) but also the Suzuki RE-5. While it’s not clear whether Norton themselves will produce a modern rotary-engined motorcycle ever again, Brian Crighton certainly might.
An engineer by profession, Crighton worked with Norton R&D in the 1980s and studied the rotary engine extensively during his time with the iconic British bike manufacturer. In fact, he worked on Norton’s 588cc rotary engine of that time and even managed to boost its output from 85bhp to 120bhp.
While Norton eventually gave up on the rotary engine and later proceeded to go bust, Crighton never gave up and managed to scrape together enough money to keep racing rotary-engined machines right up until the end of 1994, when rotary-engined motorcycles were banned from competition.
You can read the details of Brian’s 1990s racing efforts on his website here. What we want to talk about in this story is the new Crighton CR700P, which is fitted with a twin-rotor, pressurised gas-cooled 700cc engine that produces 200 horsepower at 11,000rpm and 135Nm of torque at 9,500 revs. With its custom-built aluminium twin-spar chassis, 6-speed sequential transmission (with slipper clutch) and fully adjustable racing-spec Bitubo suspension, the Crighton CR700P weighs in at just 136 kilos, so you can probably image the kind of performance it would offer.
We think the Crighton CR700P is absolutely fascinating, so we caught up with Brian Crighton for a quick chat. Here are some excerpts from what Brian had to say about his love for rotary engines and about the incredible rotary-engined bike which he’s built:
On memories from the days when he was with involved with Norton’s racing efforts in the 1980s
The most interesting memories I have from the early days is how excited the crowds got when we started winning races [with the rotary-engined Norton racebike] and how the race meeting attendances rose dramatically – people wanted to come and see a British bike beating the best of the world. It goes without saying that the rotary engine became a very serious threat to piston-engined bikes. Unfortunately, at the time the Norton factory was in great financial difficulties and rotary engine production ceased. So, sadly, it never had the chance to become a mainstream contender.
On whether the rotary engine could have been developed into a mainstream contender, had more money been available for R&D
The rotary engine has only had a very small amount of money spent on it, as compared to the vast amount of money spent on piston engine design. The other problem with the rotary engine is that they are not as fuel efficient as piston engines, but with newer materials and higher pressure injection etc., there should be big improvements in bringing them closer to piston engine fuel economy. The big Japanese manufacturers all tried the rotary engine but only Suzuki and Mazda ever put it into production. I think that if a company like Honda decided that they had to make a rotary engine bike, I'm sure that a very exciting, reliable bike would emerge!
On the new Crighton CR700P
The CR700P’s rotary engine is based on the 588cc championship winning Norton engine. The extra capacity has been achieved by making the rotors wider, but because the centre intermediate plate has been narrowed, the engine is only 4mm wider. The main difference is the way the internals of the engine are cooled. They are now cooled by using pressurised gas at around 2 bar pressure. The internal cooling path is sealed and a small, belt driven fan circulates the cooling medium through an intercooler, which is mounted in the seat unit. Because the cooling medium is so dense, it removes the heat much better than the normal unpressurised old system.
The CR700P’s chassis is an evolution of the 1994 championship winning twin-shock bike, but because of the stiffness of the swinging arm, it only needs a shock on one side. This obviously saves weight and means you only need to adjust the damping on a single shock. Due to the shock to rear wheel ratio being much smaller than the normal monoshock system, the CR700P’s Bitubo rear shock has a greater range of speed and much less damping energy, which generates much less heat and keeps the damping pretty well constant.
The front brakes use Brembo monobloc 4-piston callipers and 320mm discs which have huge stopping power. The rear uses a small AP Lockheed 2-piston calliper. The electronics used on the bike are a GEMS ECU and some interface units which I’ve made myself.
On whether he might ever build rotary-engined road bikes
With the necessary resources, we do plan to make a range of rotary-engine road bikes, which we believe would be competitive against any current production machine. We do not feel, at present, that any other manufacturer would produce rotary-engine road bikes.
We thank Brian Crighton for taking the time to speak to Faster and Faster and we wish him all the very best – hope to see a rotary-engined road bike on the streets sometime soon!!