The Rotary Nortons

Unlikely successors

Norton Rotary at the Isle of Man in John player colours
Image: Wiz Norton Racing

Rotary engines are sometimes seen as a sort of half way point between two and four-strokes. Apart from the combustion chamber, which is radically different to both, its characteristics are more aligned with the two-stroke. The bikes sound like a cross between a two-stroke and a four-stroke, a little closer to a two-stroke. Rotaries control intake and exhaust flow timing via ports, as well. Without the need for conventional pistons, conrods, cams and valves, the engine is small and light. The eccentric shaft's main bearings and the inlet manifolds are fed by oil-injection, and the fuel-air mix also carries a residual mist of oil from the interior of the rotors, which lubricates the rotor tips. Also like a two-stroke, further large scale development was halted with encroaching emission laws. The original Rotary engine was invented by German engineer Felix Wankel in 1924.

The first model Norton Rotary road bike

Norton started producing a rotary engined road bike in 1987, called the Norton Classic. Suzuki also produced a Rotary engined bike in 1974, but the engine was big, complicated, slow and ugly, the biggest lemon in their otherwise distinguished history. The Norton Wankel engine has twin cast-iron rotors in aluminium alloy cases and displaces 588cc. It was originally developed by David Garside at BSA's research facility, which came under the umbrella of Norton Villiers Triumph. The Classic was discontinued after a limited production run of only 100 motorcycles, and was succeeded by the liquid-cooled Norton Commander. Wankel engines run very hot, so Garside gave the air-cooled motor additional interior air-cooling. Air was drawn through a forward-facing filter situated to provide a ram air effect. This air passed through the interior of the rotors and then into a large pressed-steel plenum before entering the combustion chambers via twin carburetors.

The story of the Rotary racer starts with Brian Crighton, an ex-racer, who was a Service Engineer at the Norton Factory. Brian could see that the Rotary had potential as a race engine. He felt that much more power could be extracted from it relatively easily. The engine was also compact and the weight would be low in the frame. The Norton management refused to back the project but gave him a crashed Police bike to work on. Their graciousness didn't stop there though; he was also given the use of an unused caretaker's cottage so he could work on the bike in his own time.

The rotary F1

Crighton and fellow enthusiasts, Dave Evans and Bob Rowley, started to modify the engine's carburation and airflow to separate the induction and cooling systems. Initial after hours dyno tests showed 125 hp at the shaft. Amal smooth bore 34 mm carbs were used but the engine was still close to road bike trim with steel rotors and the normal 9.5:1 compression ratio. Further developmental work was carried out by the small team but in 1986, Crighton became fed up with the lack of factory interest in the project and left to work in the computer industry. However, in 1987, South African L. C. Roux took over the Norton group and showed an interest in the project.

The engine mass was smaller than a conventional engine and the weight was much lower

The Monocoque bikes

A mildly tuned version had achieved a speed of 170 mph at a test, and later on the same year, a prototype race bike scored a race win at its second meeting. The factory finally came around, and a proper race development program took place during the whole of 1988. A bike was entered for the Powerbike International end of 1988 season finale at Brands Hatch and rider Steve Spray won both races he entered. This performance led directly to the team gaining the sponsorship of JPS which continued throughout the factory teams years racing. A liquid-cooled engine was developed, and the 1989 season really put them on the map. Steve Spray won the 750 cc Supercup Championship and the British F1 title, and set lap records at Donnington Park, Thruxton, Snetterton, Brands Hatch Indy Circuit and Cadwell Park.

Published: 23 March 2010 By John Westlake

Brian Crighton was made Senior Development Engineer at Norton in 1989, and at the tail end of the year, Barry Symmons, the ex Honda Britain boss was brought in to run the works team. Crighton and Symmons didn't get on and Brian Crighton left to start on a new project, the Roton. The factory continued racing and scored 2nd and 3rd place finishes for Trevor Nation and Robert Dunlop at the Isle of Man, and Trevor Nation won the MCN TT Superbike Championship. Steve Hislop won the 1992 Senior TT, and Ian Simpson won the 1994 British Superbike title.

The original JPS team. L to R – Dave Hickman, Malcolm Heath, Trevor Nation, Brian Crighton, Steve Spray and Dave Evans

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