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Saturday, 19 October 2013

Friday bike

This week's is another 'almost' story that I remember following back in the 70s.

1976 Norton Cosworth 'Challenge'.

From here

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.

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:

The bike basically didn't have a frame as such, rather front and rear subframes along with the swingarm attached directly to the engine.

Note leading link forks
Can't help but feel that if Norton had put their money and effort into developing this bike further, especially the road version, rather than into the Rotary, the story would have ended differently. After all, this was all proven technology whereas the Rotary was a technology almost everyone else had experimented with and rejected. Had they built this engine into a conventional chassis (again all proven technology) they could have experimented further with a working bike. I can't help but feel they were trying to do too many things at the same time with very limited resources.
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.


  1. Those two Cosworths look as if they have been in a fire.
    I have a kit of parts for a JAA road engine only needs time and money to build it.
    Bob Osborn.

  2. They were burnt in the National Motorcycle Museum fire in England some years ago when a careless person disposed of a cigarette incorrectly. It was a devastating fire destroying numerous rare motorcycles including the two Cosworths