Norton’s Rotary: 1989 Norton Commander

Although Garside’s unit was small and compact for its power output, heat buildup was a major issue, especially around the combustion zone. To avoid the extra weight and complexity of liquid-cooling, Fichtel & Sachs had tried cooling the rotor by drawing intake air through its center before feeding it into the engine, but this meant the charge was heated in the process, reducing combustion efficiency. Though an intercooler would have been ideal, Garside opted instead for a plenum chamber in the intake tract where the air could lose some of its heat. It worked well enough and allowed the engine to run efficiently without a cooling fan.

In 1973, BSA merged with Norton-Villiers, part of the Manganese-Bronze group. Though a much smaller company than BSA, Manganese-Bronze was in a stronger financial position and the “merger” effectively became a takeover by Manganese-Bronze, resulting in Norton-Villiers-Triumph (NVT). Unfortunately, NVT ran out of money and ceased motorcycle production only a few years later. It was around this time that Norton acquired production tooling from Hercules after they ceased production of the W2000 rotary-engined motorcycle.

Although Norton-Triumph production was dead, there was still money to be made from ongoing developments at Norton, especially the rotary. Following the liquidation of NVT in 1978, Manganese-Bronze bought back the assets and relaunched the company as Norton Motors Ltd. In the same year, Norton registered a prototype rotary, the P42, code named Aurora. It was fitted with the air-cooled, twin-rotor 588cc engine mated to a 5-speed transmission based on a Triumph Trident unit and mounted in a new frame with Marzocchi forks, Radaelli wheels, Brembo triple disc brakes and Girling shocks.

In spite of an enthusiastic reception by Germany’s Motorrad magazine, which managed to score a ride on the factory prototype, the Aurora never went into production. Instead, Norton decided to focus on the P41, a police-spec motorcycle that was introduced in the early 1980s as the Interpol 2. Limited production of the Interpol continued, and a naked version of the air-cooled police bike was eventually sold around 1987 as the limited-edition Norton P43 Classic.

A new model intended to replace the Interpol 2 arrived in 1988 as the P52, using a liquid-cooled version of the 588cc engine. This in turn begat a civilian version using much of the same running gear and ancillaries, the P53 Commander.

The Commander story

The Commander was the product of an ambitious business plan drawn up by Philippe LeRoux, head of Norton Group PLC, which purchased Norton Motors Ltd. from Manganese-Bronze in 1987. The plan included an air-cooled naked street bike, the P43 Classic; two sophisticated liquid-cooled sport-touring bikes positioned for the police and luxury touring sectors, the P52 Interpol and P53 Commander; and a production racer aimed squarely at the 1988 Honda VFR750R, the P55 F1.

Adopting liquid-cooling meant reduced mechanical noise and allowed a boost in compression ratio for more power. The Commander’s 85 horsepower engine was still matched to a Triumph-based 5-speed transmission via a duplex chain and diaphragm-spring clutch, with chain final drive in a fully enclosed chain case. The drivetrain was hung from a box-section spine frame that also contained the intake plenum chamber and a 2-quart oil tank. A Kayaba telescopic fork was at the front and a swingarm with Koni shocks was at the rear. Much of the rest of the equipment, including the wheels, brakes, instruments and controls were borrowed from Yamaha’s XJ900. Bodywork was essentially that of the Interpol 2, with fixed luggage intentionally designed to be no wider than the fairing, although later production Commanders had removable Krauser bags.

Intake air was still drawn through the rotor core for cooling, but its flow was reversed from the air-cooled engines. The intake charge then passed to the plenum chamber to cool before being drawn via manifolds through two constant-vacuum SU carburetors. Intake air picked up lubricating oil vapor on its way through the rotor, much of which then condensed inside the frame plenum chamber. A vacuum takeoff from the left intake manifold drew excess oil out of the plenum where it was burned in the left side combustion chamber. Many owners installed a catch bottle in the vacuum line to avoid over-oiling the left rotor.

The Commander went on sale in 1988 and received a broadly positive response from testers: “None of us had any doubts that the Commander was a bit special and rather good in its intended role of sports/tourer,” Superbike wrote in 1988, adding, “there wasn’t a bike that could match its acceleration … numbers can’t convey its smoothness or seemingly frictionless turbine power.” Another tester concluded, “The only other motor I’ve tested that is as smooth is the 1,500cc flat six masterpiece in Honda’s new Gold Wing. I can easily envisage going on a long and speedy tour on the Norton. Its steady throttle performance really is exemplary.”

Criticism was mostly limited to the fact that accessing the reserve fuel tap required removing the right side bodywork and that the luggage cases were not removable. Unfortunately, at £7,500 (approximately $13,300 U.S.), the Commander was also almost 25 percent more expensive than the benchmark luxury sport tourer, BMW’s K100LT, and twice as expensive as a Kawasaki Concours. And without a dealer network, all service work had to be done at the Shenstone factory.

By 1992, despite its best efforts, Norton was badly in debt and under management by its biggest creditor, Midland Bank. Motorcycle production ceased, and in the end, fewer than 300 Commanders were built.

Roger Slater’s Commander

Former British Laverda importer Roger Slater — and with brother Richard creator of the mighty Laverda Jota — now lives near Spokane, Washington.  We met up with him at last year’s The Meet Vintage Motorcycle Festival in Tacoma, when he rode his 1989 Commander to the show.

While the Commander was never available in North America, Roger was able to restore the bike featured here and has since become very fond of his odd rotary Norton. “The outstanding feature upon first riding the bike is its utter smoothness,” Roger says, noting that its power delivery is deceiving. “It suggests a peakiness and rev-happy nature … it soon becomes apparent that this is certainly not the case,” he says. “The high torque from virtually zero revs is an outstanding feature. Certainly the engine will rev like a turbine and can be ridden like a sports bike — but there is no need.”

Roger likes to revel in the engine’s broad torque band, trickling through small towns at 25mph in top gear, then opening the throttle without downshifting, taking off with “the sound of a turbo prop plane engine,” he says.

“Handling is of normal Norton high standards. Steering is absolutely neutral, with none of the top-heavy wrestling that plagues so many modern tourers. Suspension is comfortable front and rear, very similar to BMW. On long trips I find myself likening the Norton to a magic carpet as it wafts so effortlessly along at almost any speed one requires,” he says.

One thing Roger has changed is the front disc brake, replacing the two-piston calipers with larger discs and four-pot Brembo calipers.

Like any bike, the Commander has its shortcomings. “One weakness that I have worked very hard to eliminate is a modest reluctance for the gearbox to find neutral once stopped,” Roger says. Period test reports confirm that the Commander’s shifting is not perfect, the likely culprit being the selector mechanism in the Triumph-derived gearbox and the clutch design — though excessive undercut on the engagement dogs may also contribute.  “The habit of selecting neutral before rolling to a stop has to be adopted,” Roger says. “Another issue is the time it takes to get going again after a stop, simply because of many questions from the mob surrounding the bike!”

Roger cites a few more improvements he would have liked, like a fuel tap on both sides of the tank, a larger radiator cooling fan, and revised wiring to make the dashboard glove boxes usable instead of just being access panels to the fuse box. And like period testers, Roger would like the hard bags to be detachable.

“Overall the bike is an outstanding testament to what can be done with a small, dedicated team of engineers on a bootstrap budget. Had the bike been further developed I would expect to see (these) minor glitches addressed.

“Setting these bikes up correctly is a most interesting and pleasant learning experience,” Roger says. “Forget everything about so called ‘normal’ bikes. Once correctly fettled the Norton rotary is a bomb-proof, long-lasting engine.” Roger credits Richard Negus, former head of Norton Motors Ltd., with help preparing engine parts, including molybdenum coating of the chamber sealing surfaces inside the engine.

The Commander looks bulky and unwieldy, but as I discover during a quick spin it feels light and easy to handle from the seat. Roger’s fitted handlebar risers, so the seating position behind the tall windshield is upright. The engine fires immediately on the starter and settles easily to a burbling idle. The clutch is light, and though Roger has advised that the transmission may be temperamental, I have no problem selecting first. Pulling away is a breeze, and I’m reminded of a Yamaha FJR1300, so smooth and tractable is the engine. I follow Roger’s advice to select neutral before coming to a stop, so I don’t get stuck in gear.

Shifting is light and acceleration is brisk, and the engine surprisingly smooth and quiet — just a rustle from the engine and a 2-stroke-like drone from the exhaust. And like a 2-stroke, the engine offers almost no braking on deceleration, so I’m glad of Roger’s front brake upgrade. Handling is neutral, the bike feeling light and nimble in the turns, and easy to maneuver at low speeds. It’s deceptively quiet and still behind the large windshield, and I can imagine covering hundreds of cross-country miles in dignified peace and comfort.

With the passing of the Mazda RX-8 in 2011, rotary-engined road vehicles have become extinct. But the Norton rotary engine lives on, still manufactured for use in drone aircraft where its light weight and compact size are prized. But like so many in the British motorcycle industry, the Norton Commander story remains a “what if … ?” MC

Read more about the Norton Commander

The Rotary Wankel Engine
Rotary-Powered Nortons: From Commander to F1