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.
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.
Engine was fairly interesting:
Found this sad picture of a couple of Challenge engines, don't know what happened, but they look like they've been left lying out in the open for 20 years.