Rotary Returns

Remember the Norton rotary? Looks like it's making a comeback (but not as a Norton)

Report: Peter Henshaw

If you were a motorcyclist in the 1980s and early '90s, you couldn't have failed to notice the twists and turns of the Norton rotary story. More convoluted than an alpine switchback, it was. Back in the early 1970s, when the BSA motorcycle empire was close to collapse, it was experimenting with an air-cooled rotary engine. The rotary (also known as the Wankel, after its inventor Dr Felix Wankel) would see limited use by Mazda and NSU in cars, and DKW and Van Veen in motorcycles.

Eschewing up-down pistons for a trochoidal piston which just spun, this radical motor promised unrivalled smoothness and fewer moving parts than a conventional engine. Unfortunately, sealing that trochoidal combustion chamber proved tricky and the rotary also suffered from poor emissions.

Undaunted, BSA's successors – first NVT, then a barely surviving Norton – persevered with the concept into the 1980s, when Norton began building the rotary-engined Interpol 2 for the police, following that up with a civilian bike and an updated liquid-cooled version of the twin-rotor motor. Although the bikes had their fans, it was all on too small a scale to survive and Norton motorcycles collapsed in a welter of corporate shenanigans. The Norton name, now

Above: essential information – the CR700 is a single-minded machine Below: Norton Classic was an air-cooled rotary was sold to the public (Photo: Mike Jackson)

owned by TVS of India, seems to have finally secured a stable future, though current plans don't include the rotary.

That might have spelled the end for the whole rotary motorcycle story, were it not for one Brian Crighton. Crighton, who worked for Norton, was the man behind the rotary bike's extraordinary run of racing success from the late 1980s and early '90s, attracting high profile sponsorship from Imperial Tobacco. Multiple short circuit race wins culminated in Steve Hislop winning the Senior TT in 1992 – it was the first time Norton had won a TT since 1961, and it was a glorious moment.

Power Breakthrough

Thirty years after that TT win, it looks as though the Crightondeveloped rotary is being revived, with a motorcycle (not road legal, for track days only) launching this year, followed by a road bike in 2024. Strangest of all, this revival seems to be centred on a factory in the heart of Dorset, whose main business is making paramotors and jet boards. I found Brian Crighton in his Dorset workshop, surrounded by rotary engine parts, and asked how this revival had come about.

“In the '80s I was a Honda dealer in Brownhills but went to work for Norton in Shenstone,” he told me. “I could see that the rotary had potential for a lot more power so I was always pushing them to go into racing. In the end I developed a racing bike myself, based on a crashed police bike which was spare at the factory. I worked evenings and had help from some of the lads there, paying for parts myself. The standard air-cooled rotary gave 85bhp but I was sure it could make 120, with a bit of development, which it did the first time we ran it.”

The secret to liberating this dramatic increase was sorting out the rotary's breathing. Rotary engines tend to produce a lot of heat and as developed by Norton, this air-cooled version was 'charge cooled', with the intake air sucked through the middle of the crank before heading into the airbox and carbs, thus helping to cool the engine's internals on the way through. This enabled the air-cooled engine to run well on the road, but it strangled the breathing.

Brian Crighton's answer was the ejector exhaust system, which used a venturi in the exhaust to radically speed up the flow of gases, creating a powerful vacuum to suck the intake through more quickly. “That opens up the engine to give a lot more power. It's quite a simple idea, but it works, sucking the heat out as well as increasing power.” The result wasn't peaky either according to its inventor – “you could tootle along at 1000rpm if you wanted.”

But Norton didn't have the funds to go racing on its own account, so Brian ended up leaving to develop the race bike on his own. Being a small team run on a shoestring, they desperately needed sponsorship, and their big chance came at a Brands Hatch meeting when reps from Imperial Tobacco, owner of the JPS brand, were there. JPS of course, had form, having sponsored Norton's earlier race team in the 1970s.

Ron Haslam on a racing rotary – the bikes had a string of race wins in the late 1980s/early '90s (Photo: Timothy B./Pintrest)

“Steve Spray had never ridden the bike before,” remembers Brian, “but got on with it straight away. When he came back from practice we said what do you want us to change? 'Nothing,' he said, 'just put petrol in it!' Then he went off and won both main races, the crowd went mad and the JPS reps agreed to sponsor us – they gave us £1 million over three years.

“We had Steve, Trevor Nation and Simon Buckmaster riding for us. We were starting from scratch really, developing as we went, but the results started to come through. The JPS bikes had so much top speed, they'd be passing the Yamahas and Suzukis on the straights. We went to Sugo in Japan for a WSB round against all the works teams with Trevor Nation riding – there's a long start/finish straight at Sugo and Trevor was passing the works bikes on his back wheel, almost vertical! We were penalised for that.

“The only races we didn't win were in the wet. The rotary engine is producing power for about 200 degrees, rather than in pulses like a piston engine, so it did suffer from wheelspin. I later developed an electronic traction control system, which no one else had in 1995.

“We were up to about 135bhp, thanks to porting and eventually higher compression, which was about the same as the opposition, but the bikes were a lot lighter, about 135 kilos, so you could brake later and steer quicker. By 1989 we had the lap record on every circuit in the country and won the Championship." Norton was able to capitalise, building the F1 sports bike, based on the racers, but the rotary's winning streak was about to come to an end. “After winning the '94 Championship we were banned,” says Brian. “I think Honda were a bit fed up with us beating the RC45... Also by then Norton had just about gone bust so we didn't have a road bike frame to base the bike on.”

Brian then went to work for the National Motorcycle Museum, where he restored the rotary racers for Roy Richards and built a replica of what would have been the 1995 race bike, with traction control and variable intake geometry – the latter altered the length of the inlet tract by up to 120mm to produce good

Left: early days at BSA, bench testing the prototype rotary engine Right: Rotary engines (this isn't a Norton) use a trochoidal piston (Photo: Londo Mollari)

torque throughout the rev range. A spell as Technical Director for the Stuart Garner-led Norton followed that, but seeing how the business was run, Brian soon decided to leave...

New Rotary

That might have been end of the whole rotary motorcycle story, except that Brian was approached by one Gilo Cardozo. Gilo built paramotors – a powered hang glider with the motor and propeller strapped to the pilot's back – and in 2007 was planning an attempt on the paramotor altitude record by flying over Everest with professional adventurer Bear Grylls. What they needed was a lightweight, compact engine of high power, and Brian helped develop a supercharged rotary which fitted the bill. On the day, the supercharger on Gilo's paramotor failed at 28,000ft, but Bear Grylls carried on climbing, and bagged the record.

That led to a call from the MOD, which was also on the look out for a compact motor to power drones and unmanned helicopters. As a result, Cardozo's company Parajet now makes a whole range of interesting devices including very trick (and expensive) rotary engines for drones, more conventional paramotors and the Jet Board, which is best described as a short-wheelbase surfboard with a two-stroke engine hidden inside its carbon-fibre skin. There's also the SkyQuad, a sort of flying dune buggy which is fully road legal. The factory is an interesting place...

But for motorcyclists, the really interesting story lies in Brian Crighton's workshop, and the fact that that the factory is gearing up to produce its first bike. This is the CR700W, based around a Spondon alloy frame and powered by the latest version of that rotary engine. All components will be top notch, with Dymag carbon-fibre wheels, Brembo brakes and Ohlins or Bitubo forks and rear shock.

As for the engine, it's the culmination of Crighton's painstaking development over the years, incorporating the ejector exhaust and variable intake tract, plus fuel injection. The motor now displaces 690cc with a pressurised gas-cooling system driven by an external pump which circulates the gas through an intercooler in the tailpiece. They're claiming 220bhp with 105lb ft torque peaking at 9500rpm, though according to Brian it's not a peaky delivery. “The torque curve is flat and the power curve is straight, so it's a very nice bike to ride.”

If the CR700W has a secret weapon, then it's likely to be weight. According to Gilo Cardozo, the production bike will weigh just 129kg, or to put that in context, it'll have Moto GP power with the weight of a scooter. What it won't be is road legal, and a batch of 25 CR700Ws is being planned to sell for track day use only. If all goes to plan, these will be assembled by Brian (price, around £85,00 plus VAT) before a less expensive road version follows in the spring of 2024. Thanks to die casting and other measures, that should come in at about £45,000, though again it'll be a limited edition. “We're planning to make 250,” says Gilo, “but if there's a demand for 500 then we'll make them. Each bike will be tested on Single Vehicle Approval, for which rotary engines are exempt from the emissions test.” I've checked, and he's right.

So, the Norton rotary story isn't over yet and might even be entering a new era in the last years of new petrol-engined bikes. If this is a swansong for petrol-powered motorcycles, then they're going out on a good note.

ejector exhaust was the secret to liberating more power