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Norton 750 JPS Monocoque

1973 Norton 750 JPS Monocoque

Short-lived success
With tobacco giant John Player’s support, Norton (which was restricted to production derived machines) returned to competition in 1972, in the 750 class. During its first year, the team used a modified Commando engine and a tubular frame. But the team’s boss and chief development engineer, Peter Williams, was convinced that a monocoque frame was the right way to go. He created the Norton JPS Monocoque, which only raced in 1973.

Lack of Finance
The idea was to create a lighter, lower, more aerodynamic bike, but – lacking funds Williams was forced to make compromises. Instead of being in light-alloy, the frames were made of stainless steel, which proved as heavy as the tubular frames. Moreover, the mechanics complained about the difficulty of working on the enclosed engine.

Tourist Trophy Winner
Williams had the only machine ready in time for Daytona in 1973, but had carburetion problems. During the Anglo-American Easter series of six short races on three British circuits – Brands Hatch, Mallory Park and Oulton Park – Williams won three races and finished first overall. Williams then beat Barry Sheene (Suzuki) at Cadwell Park and won the 750 Formula Isle of Man TT with a record lap of 107.2 mph. Factory policy caused Norton to abandon the monocoque, replaced in 1974 by a multi-tube girder frame. Williams, who gave up racing after an accident in 1974, later designed and developed Formula 1 car engines for Cosworth Engineering, which were used by McLaren and Benetton in 1993.

SPECIFICATIONS
Engine: 745cc (73×89mm) air-cooled single cylinder four-stroke; Lucas electronic ignition
Power Rating: 74 hp @ 7000 rpm
Valves: overhead
Fuel System: two Amal GP carburetors
Transmission: 5-speed, chain primary and final drive
Suspension: telescopic forks (front); swing arm (rear)
Brakes: twin discs (front); disc (rear)
Wheels: 18 inch aluminum (front & rear)
Weight: 340 lb
Maximum Speed: 160 mph

The monocoque chassis of the 1973 Norton 750 JPS was made of stainless steel. Its creator, Peter Williams, is shown (inset).

Norton 750 JPS (Spaceframe)

1974 Norton 750 John Player Special

Third time unlucky
During its three years of existence, the John Player Norton team used three different cycle parts. Following the classic tubular frame of 1972 (derived from the Commando) with a large-diameter top tube and small-section auxiliary tubes, in 1973 the team used a stainless-steel monocoque devised by Peter Williams, who rode it to a record victory in the Isle of Man IT. Finally, for the 1974 season, a trellis girder frame was adopted.

Political Decision
Why had Norton abandoned the monocoque, which had been so successful? Williams, who later worked on Ford Formula 1 engines at Cosworth, commented: “I was against the change, but though the team seemed fully aware of my success as designer and rider, they decided to replace the monocoque. In my opinion, it was a political decision.”

Lack of Success
“You’ve never seen so many tubes in one frame,” declared Motor Cycle magazine. The new trellis frame (similar in concept to the Ducati’s) was faithful to the theory of the monocoque, with a load-carrying backbone surrounding the engine. The mechanics, who were all for the change, claimed it was lighter and made it easier to work on the engine. Williams said that the monocoque would have been considerably lighter for 1974. The second generation 749cc Commando engine replaced the old long-stroke (73×89mm) unit but was only a little more powerful, and the 1974 JPS was never fast enough to counter the new wave of Japanese two-stroke multi-cylinders.

SPECIFICATIONS
Engine: 749cc (77×80.4mm) air-cooled V-twin four-stroke; Lucas coil ignition
Power Rating: 78 hp @ 7500 rpm
Valves: overhead
Fuel System: two Amal GP carburetors
Transmission: 5-speed, chain final drive
Suspension: telescopic forks (front); swing arm with twin spring/dampers (rear)
Brakes: Lockheed; twin discs (front); disc (rear)
Wheels: 18 inch Dunlop tires on cast magnesium wheels (front & rear)
Weight: 331lb
Maximum Speed: 165 mph

The cantilever spine of the 1974 Norton-JPS was made up of many short, straight tubes. Sadly, the engine lacked the power to match the new generation Japanese works bikes.

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Norton 750 Cosworth Challenge

1976 Norton 750 Cosworth Challenge

Norton’s last stand
The last racing Norton with a conventional power unit – rather than a rotary – was the Cosworth-powered Challenge of 1975.

New Start for Norton
Its history began in 1971, when Dennis Poore, who had just bought Norton after the failure of the Associated Motorcycle Group, tried to promote the marque by returning in 1972 to competition in the livery of John Player.

25 Percent of a GP Engine
The old Commando wasn’t powerful enough, so Poore decided to buy time with specially tuned versions, while waiting for a design study from Cosworth, known for its racing automobile engines. The Cosworth-Norton JA engine – code-named “Challenge” – was a racing-plus-production design. The road JAB version was to develop 65 hp and the racing JAA “whatever we could get out of it,” recalled Keith Duckworth of Cosworth. The engine was designed to be part of the frame, but there were cooling problems and by the time the engine was tested and ready, Norton-Villiers-Triumph was in financial trouble. Cosworth built 30 JAA prototypes, the production bike was canceled and an underfunded racing program ended. In 1984, a couple of JAA engines were bought by Quantel, and four years later, the JAA engined Cosworth Quantel proved the worth of the design by winning at Daytona.

SPECIFICATIONS
Engine: 747cc (86×65mm) water-cooled Cosworth JAA 360-degree parallel-twin four stroke
Power Rating: “at least 110″ hp @ 10,500 rpm
Valves: twin overhead-camshafts driven by cogged belt
Fuel System: twin Amal carburetors (988, fuel injection)
Transmission: 5-speed, chain final drive
Suspension: telescopic forks (front); cantilever with monodamper under the engine (rear)
Brakes: twin discs (front); disc (rear)
Wheels: magnesium; 16 inch (front); 18 inch (rear)
Weight: 375 lb
Maximum Speed: 171 mph

The Norton Challenge was brought down by the failure of NVT. Pictured is one of its few track appearances, with Dave Crockford practicing for the 1976 Imola 200 miles.

Quantel Cosworth