Paul d'Orléans

A Short History of Wankel Motorcycles

The revolutionary rotary engine designed by Dr. Felix Wankel, henceforth known as the Wankel engine, is a design of tremendous promise, and expensive vexation.  It seemed the wonder motor of the future in the 1960s, and many automobile manufacturers took a out a license on the design, from General Motors to Rolls Royce, as did many aircraft and

motorcycle manufacturers.  The difficulties of making a Wankel engine suitable for a road vehicle are legendary, but can be summed up simply: the gas-sealing tips of the rotors were prone to rapid wear, the engine is very thirsty, and as the rotor tips must be lubricated, it's a 'dirty' engine as measured by emissions, much like a two-stroke.  Most manufacturers quickly realized these difficulties with their prototypes, and abandoned the Wankel motor after a few hundred test miles.  A few manufacturers doubled down on the idea, developing clever methods of solving the Wankel's inherent problems via high technology (as in the Suzuki RE5) or excellent engineering (Norton and Mazda).

Dr. Felix Wankel (born 1902 in Lahr, Germany) had the vision for his remarkable rotary engine at the age of 17, began working on prototypes 5 years later, and gained his first patent for this remarkable engine in 1929. His work on the motor was slow in the following two decades as he developed rotary-valve applications for piston engines. By 1957, working in conjunction with NSU, he had a fully functional rotary engine prototype, and immediately began licensing the engine, which had many theoretical advantages over a typical piston motor. First to take up this new design was aircraft engine builder Curtiss-Wright, who licensed the design on Oct.21, 1958. Curtiss-Wright has a long and deep motorcycle connection, via founder Glenn Curtiss, but their Wankel engines were mostly used in aircraft. The first motorcycle applications for this promising engine appeared shortly after the first rotary-powered automobiles, the Mazda Cosmo and NSU Spider of 1964.  The first motorcycle prototypes appeared earlier, in 1960, which is the start of our survey of this remarkable design.

Motorrad Zschopau (MZ)/ IFA

The first motorcycle application of the Wankel engine emerged from the IFA/MZ factory, from 1960. MZ took out a license from NSU in 1960, to develop Wankel engines as possible replacements for their two-stroke engines in both motorcycles and the 'Trabant' 3-cylinder two-stroke car. Within 3 months, a single-rotor, watercooled engine (using the thermosyphon principle rather than a water pump?) of 175cc, was installed in an IFA chassis (the 'BK 351' of 1959) which formerly housed a flat-twin two-stroke engine. The development team included engineer Anton Lupei, designer Erich Machus, research engineer Roland Schuster, plus machinists Hans Hofer and Walter Ehnert, who deserve credit as the first to build a Wankel motorcycle.

The Wankel motor is neatly mated to the existing IFA gearbox (with shaft drive - similar to the BMW R25 gearbox), and developed 24hp, twice that of the comparable 175cc MZ two-stroke engine. The prototype appears to have been extensively tested, and currently has over 38,000km on the odometer. It lay in obscurity for years, before a 1994 exhibit of MZ history at Neckarsulm brought it back to light.

A second prototype was built in 1965, using a new 175cc air-cooled, single-rotor engine, also producing 25hp, considerably more than the ES250 'Trophy' engine normally installed in this chassis. This engine appears very much based on the Fitchel and Sachs engine, which was well-developed by 1965 and being sold under license worldwide. Despite the success of both MZ engines, inevitable problems with rotor tip seal failure and high engine/exhaust temperatures meant lots of development money would have been required to replace their reliable two-strokes... money which MZ didn't have. Their incredibly successful race program (all two-strokes, designed by the genius engineer Walter Kaaden) was practically created out from the factory scrapheap, with little help from the Socialist functionaries controlling industry in the GDR.

The idea of a simple, robust, and compact rotary engine was very appealing in the early days of Wankel development, but the dream proved unrealistic, as it became clear production machines required terrible complexity for acceptable road use. East German engineers created several prototype engines for the Trabant and Wartburg autos, but none were developed beyond the prototype stage, and the NSU license was allowed to expire in 1969.

Yamaha

Yamaha licensed the Wankel design in 1972 and quickly built a prototype, showing the 'RZ201' at that year's Tokyo Motor Show. With a 660cc twin-rotor water-cooled engine, it gave a respectable 66hp @6,000rpm, and weighed 220kg. While the prototype looks clean and tidy, the lack of heat shielding on the exhaust reveals the Yamaha was nowhere near production-ready, given the searing heat of the Wankel exhaust gases, and subsequent huge, double-skinned, and shielded exhaust systems on production rotaries.

During this period, Yamaha was looking for alternatives to its small-capacity two-strokes, developing large rotary, two-stroke, and four-stroke engines. With 'shades of George Brough' (ie, showing prototypes to 'wow' show-goers), another never-manufactured Yamaha design was shown in 1972, a 4-cylinder two-stroke - the TL750.

Suzuki

One year after Yamaha introduced, but never manufactured, their rotary, Suzuki introduced the RE5 Rotary at the 1973 Tokyo Motor Show. Suzuki licensed the Wankel engine on Nov.24, 1970, and spent 3 years developing their own 497cc single-rotor, water-cooled engine, which pumped out 62hp @ 6500rpm. Styling of the machine was reportedly entrusted to Giorgietto Guigiaro, a celebrated automotive stylist and advocate of the 'wedge' trend in cars, who leaked into the motorcycle world via several projects, notoriously the 1975 Ducati 860GT. Guigiaro's touch extended only to the cylindrical taillamp and special instrument binnacle for the RE5; a cylindrical case with novel sliding cover, meant to echo the futuristic rotary engine... the rest of the machine looked nearly the same as Suzuki's GT750 'Water Buffalo'.

The modest power output of the engine, combined with the 550lb wet weight, meant performance wasn't exciting, with a top speed of 110mph; no better than the two-stroke T500 series it was meant to displace, and far more complex, heavy, and expensive. Unfortunately, the release of the RE5 coincided with the Oil Crisis of '73, and customers suddenly became wary of the rotary's reputation for poor fuel economy. This combined with motorcyclists' typical skepticism of anything too new, meant sales of the RE5 were far lower than required to recoup their investment. With millions at stake in the project, Suzuki were determined to carry on production. Blaming Giugiaro's binnacle, in 1975 the styling was more conventional, but sales didn't improve, and by 1976 Suzuki had swallowed their losses, and shut production. Around 6,300 were built.

Hercules / DKW

Fitchel and Sachs were the second licensee of the Wankel engine, on Dec 29, 1960, and the first with a motorcycle connection, with 'Sachs' the largest European maker of two-stroke engines. Sachs built their rotary as a small, light accessory motor for applications as diverse as lawnmowers, chainsaws, and personal watercraft.

The first two-wheeled mass-production of the Wankel engine was the 'Hercules' W-2000 of 1974, with a 294cc/20hp (later 32hp) air-cooled engine, with a single-rotor, which had previously been used in a snowmobile. The prototype machine used a BMW R26 gearbox and shaft drive, but production W-2000s used a 5-speed gearbox and chain final drive.

The Hercules was good for 82mph (later 94mph), and was the first production motorcycle using a Wankel motor. The first models used a two-stroke mix in the petrol to lubricate the engine, which was later upgraded to an oil injector; smoky in either case! About 1800 were sold under both Hercules and DKW badges between 1974-76. In 1977 they sold all their production tooling to Norton.

Hercules also built a few off-road Wankel-engined motocrosser, for the ISDT and for their US importer Penton Motors.   A few of these showed up in the USA, and vex the experts on MX history, as they're very rare.  The crankshaft was mounted nearly vertical, presumably to give a shorter wheelbase and better cooling, and while the engine might look like a two-stroke, a close look reveals the truth about the Hercules MX Wankels.

BSA / Norton

BSA felt, in common with most of the automotive industry, that the Wankel was the engine of the future, and in 1969, hired David Garside, a gifted young engineer, to begin exploration of Wankel engines for a motorcycle. Market research indicated the motorcycling public would accept the Wankel engine on fast sports machines, and Garside's small team began experimenting with a Fitchel and Sachs single-rotor engine, and with significant changes to the intake system, gained a staggering 85% more power, to 32hp. Suddenly the experimental engine looked appealing.

Economic catastrophe at BSA meant development was immediately stalled. 1973 was the end of BSA, as the British gov't formed NVT - Norton-Villiers-Triumph...BSA was dropped from the title, even though it had owned Triumph since 1951! Still, under Dennis Poore's thoughtful leadership, the rotary project continued, and it was Norton who licensed the Wankel design on July 25, 1972.

David Garside and his team began physical research with the installation of a Sachs fan-cooled single-rotor motor in a BSA 'Starfire' chassis; this was the first of a long line which led to the famous Norton rotaries. The 294cc engine gave 32hp at 5500rpm, and evidenced significant problems with heat - with twice the combustion events per revolution compared with a piston engine, and a physically much smaller engine unit, heat is a significant issue with Wankels. Sachs dealt with heat by routing the incoming air through the rotor itself, but this heated up the incoming mix, which reduces power. Garside redesigned the intake route, so that it still cooled the rotor, but then passed into a plenum chamber to cool off again. Air passing through the engine entered the plenum at 100ºC, but was cooled to 50º by the chamber and atomized petrol.

In this work, Garside was helped by Bert Hopwood, retired BSA and Triumph designer (a protogé of Edward Turner, and author of the excellent 'Whatever Happened to the British Motorcycle Industry'), and the pair added a second rotor to the Sachs engine (giving 588cc), with many times the original finning area, plus that redesigned intake. The engine was installed in several chassis over the years, from a Triumph 'Bandit' to a Norton Commando, but eventually an entirely new chassis was developed, as the engine showed considerable promise during development.

The first twin-rotor engine was installed in a Triumph 'Bandit' chassis in 1973, which was never shown to the public. With nearly 70hp, about twice the 'spec' of the original dohc Bandit twin-cylinder piston engine, this prototype must have been a lively ride!

It was clear a new chassis was needed, and later in 1973 the Wankel appeared in a new frame, with a large spine tube which held oil; various iterations can be seen with Norton or Triumph tanks, as the engine was developed, in 1973/4: these were code named the 'P39'.

After the merger of Norton and BSA/Triumph in 1973, another chassis was created for the rotary Norton, with box-section frame tubes - still holding oil - and an integrated airbox; the 1978 'P42'. With a Triumph T140 5-speed gearbox, this wholly new Norton was intended for production, and enough material collected for a first batch of 25 machines, but the project was halted suddenly, even after brochures were printed and journalists (notoriously, Cook Nielsen of Cycle World) invited to test it.

It took until 1984 for Norton to gear up production, but the 'P42' model was never sold to the public; it became the 'Interpol II', a police motorcycle; Norton had a long history of supplying the police, with the original Interpol Commando built from 1970-77. The Interpol II used Norton's well-developed 588cc air-cooled twin-rotor engine gave 85hp, and was in production from 1984-89, with around 350 built.

The first Norton civilian rotary was the 'Classic', built as a limited edition of around 100 machines in 1987, which sold out quickly. It was essentially an Interpol II in civilian garb, with a traditional Norton silver-and-black paint scheme. With all the bodywork removed, the 85hp engine gave sporting and smooth performance, very reliably, having been de-bugged using feedback from police agencies. The engine weight was low, making for easy handling.

As Norton continued to develop their rotary, water-cooling was a natural next step to deal with heat issues, and in 1988, an Interpol II with a radiator was introduced, the 'P52'. The civilian version, essentially a re-painted Interpol, was the p53 'Commander', produced from 1989, with 85hp on tap. Norton hoped to repeat the success of the Classic, but the machine was criticized for using merely adequate Yamaha wheels and suspension, and not the sporting items one might expect of the Norton marque. Around 300 Commanders were built.

Such disappointments were rectified in 1990, when Norton finally lived up to its heritage and introduced the lovely 'F1' ('P55'), based on their RC588 racers, then in the midst of a terrific run of success on the racetrack; in 1989 they won the British F1 championship. Only one color scheme was offered, in race sponsor 'John Player' livery of black and gold. Power was bumped to 95hp@9500rpm, from the water-cooled engine. The F1 had issues with heat buildup, as the bodywork almost sealed the engine unit within plastic, and lost quite a few hp when ridden hard. Around 145 F1s were built. Built with a Spondon aluminum twin-spar frame, White Power upside-down forks, a Yamaha 5-speed gearbox, and stainless exhaust, the F1 sold for an expensive £12,000.

In 1991, Norton rectified the heat issues by introducing the F1 Sport ('P55B'), which was effectively a F1 Replica, using the same bodywork as the racers, with more air flow possible around an open fairing, which resulted, curiously, in a less expensive sportsbike. Some consider the F1 Sport the finest of all the rotary Nortons. 66 were built, before Norton's eternal financial troubles put an end to rotary production...for now.

Van Veen

In 1976, Henk vanVeen, the Dutch Kriedler importer, saw potential in the new rotary Comotor engines, which were compact and developed good power. Comotor was a joint venture of NSU and Citroen, who invested huge sums developing a new Wankel engine for the Citroen GS Birotor. The prototype of this engine had been extensively tested between 1969 and '71 in the Citroen M35, which was never officially sold, but 267 were given to loyal customers for beta-testing. The M35 engine used a single rotor rated at 47hp, whereas the later GS engine had two rotors, and produced 107hp from a 1,000cc. Van Veen saw this powerful and compact engine as the basis of a new superbike, and created the VanVeen OCR 1000.

The OCR was a heavy machine at over 320kg, but had good performance, with a top speed of over 135mph, and could hit 125mph in under 16 seconds. The water-cooled engine was housed in a Moto Guzzi chassis, used a gearbox designed by Porsche, and sold for $15,000, the same price as a Lotus Elite! 38 VanVeen OCRs were built before Comotor went into liquidation, as the GS Birotor was an utter flop, a gas-guzzler appearing exactly during the 1973 oil crisis, and worse, it was more expensive than the venerable Citroen DS, and slower. Citroen even tried to recall and destroy all examples, but a few survive. The VanVeen OCR, on the other hand, has always been a coveted and expensive collector's motorcycle.

Honda

Honda's engineers did investigate the Wankel craze of the mid-1970s, although they never produced or even licensed the Wankel design.  Housed in a nearly stock CB125, this test-bed project was clearly intended to see if Honda was missing out on the Next Big Thing.  This prototype looks to have been built around 1973, given the paint job and spec of the CB125 'mule'.

The little Honda rotary is an unlicensed experiment, strangely grafted atop a CB125 crankcase, with a single rotor that was air-cooled, although an oil cooler was added to keep the temperature down from the notoriously hot-running Wankel design.  The actual engine was connected to the standard Honda crankcases via a chain to the primary drive, while the crankshaft area was simply empty.  The single tor chamber had a capacity of 124.7cc and a compression ratio of 8.5:1, giving 13.5hp @ 8000rpm. A 28mm Keihin carb was used, with twin spark plugs and a petroil mix at 100:1.

By the time the Honda A16 was finished, the Suzuki RE5 would have already been in production, and the tepid response to this radical new model was noted.  Honda, by waiting out the early Wankel craze, saved itself considerable development and production expense.

Kawasaki

Kawasaki joined the fray later than its Japanese rivals.  The 'X99' prototype had a twin-rotor engine, water-cooled, which purportedly developed 85hp. Kawasaki Heavy Industries, Ltd, purchased a license to built Wankels on Oct. 4, 1971; the chassis of the X99 appears to be based on Kawasaki's Z650, introduced in 1976, which suggests the date of this prototype.

VNII-Motoprom

The city of Serpukhov, 100km from Moscow, was one of many 'secret' towns in the Soviet Union, where research into new technology was conducted (plus manufacture of the AK-47), far from prying eyes. VNII-Motoprom was an auto and motorcycle research institute, which created quite a few interesting machines, most notably Soviet racers such as the Vostok-4, and a few Wankel-engined bikes, completely unlicensed. The story of the Soviet motorcycle industry is little known in the West (and the East!), and deserves exploration...

In 1974, the RD501B used the ubiquitous BMW R71-based chassis (from a Dnepr MT-9), with a fan-cooled engine, clearly a copy of the Sachs rotary. With 495cc, it developed 38hp @6300rpm, and used shaft drive. It is claimed two were built.

The RD-660 prototype was built in 1985, using a 660cc air-cooled twin-rotor engine, with chain drive. The engine is very similar to the BSA/Triumph/Norton prototypes built since 1973...a little Cold War industrial espionage not doubt, but methinks the Soviets bit off more than they could chew with the Wankel motor, as none were produced in series, in cars or motorcycles.

The RD-515, RD-517, and Rotor V-500 prototypes of 1987 used a water-cooled twin-rotor engine, driving through a Dnepr gearbox and shaft drive. Power was claimed close to 50hp, with great mid-range torque, and while the prototypes had modern cast-alloy wheels (still with drum brakes), these proved inadequate for Russian roads, and apparently tended to break.  This was the last Motoprom Wankel exploration.

IZH

Little-known outside the Eastern Bloc, Izh is the oldest Soviet/Russian motorcycle manufacturer, founded in 1929 in Izhevsk (on the banks of the Izh river) as part of Stalin's enforced industrialization of the agrarian economy, begun in 1927 with the rejection of Lenin's 'New Economic Policy', which allowed producers of grain or goods to sell their surplus at a profit - very similar to China's first moves toward Capitalism in the 1990s. Stalin's successful effort at creating an industrial power, where none existed previously, actually decreased the standard of living, caused widespread famine, and meant imprisonment or death for millions...although it did create an automotive and motorcycle industry. Not that 95% of Soviet citizens could afford it in those early days, although Izh sold something like 11 Million motorcycles before 1990.

One of the last hurrahs for Soviet-era Izh was this Wankel-engined prototype of surprisingly contemporary, if clunky, aesthetics. The 'Rotor Super' was under development at the end of the Soviet era, and shown just after the fall of the Berlin wall in 1989, when the Russian economy was in relative chaos. Suddenly without the state business subsidies and guaranteed incomes of potential customers, all Soviet-era businesses were suddenly faced with the need to make a profit, and rash ventures such as Wankel superbikes were out of the question. Izh is still in business, making inexpensive small-capacity motorcycles.

Crighton Racing

Brian Crighton joined Norton Motors in 1986, as a service engineer working on their Wankel models.  He was promoted to their R&D department, and began developing a scrap 588cc air-cooled Norton engine, raising output from 85hp to 120hp.  The engine was installed in a prototype racer in 1987, which hit 170mph on tests, and scored a victory on its second outing. Realizing they had a winner, Norton found sponsorship with JPS, and in 1989 Steve Spray won the British F1 and SuperCup championships.  Crighton split from the Norton team in 1990, and teamed with Colin Seeley as Crighton Norton Racing, competing against factory GP two-strokes of the era.  Their swansong was the British SuperCup Championship in 1994, after which the Wankel engines were banned from competition.

Crighton still believed in the possibility of lightweight, simple, and ultra-powerful Wankel engines for high-performance motorcycle work. In 2006 the 'new' Norton announced the NRV588, Crighton's latest version of the Wankel racer, with 200hp and 300lbs, but the project was abandoned as Norton moved towards producing their vertical twin machines based on the Kenny Dreer prototypes. In 2017, Crighton announced a partnership with Rotron to build the CR700P, a limited-edition version of the NRV588, a 200hp lightning bolt weighing a mere 399lbs (136kg), with 100ft-lbs of torque at 9500rpm, which is a GP-level mix of high performance and ultra light weight.  The CR700P was announced as both a street and a road model, although passing Euro4 environmental and safety regulations seems all but impossible for the road for such a machine, barring a significant infusion of capital.  Brian Crighton is a true keeper of the flame for the Wankel engine in motorcycles.

 

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by Paul d'Orléans