The 750 cc (46 cu in) DOHC vertical twin was essentially two cylinders from Cosworth's world championship winning V8 DFV Formula One engine.
By 1973 the British motorcycle manufacturing industry was in trouble, no longer able to compete in world markets with mass-produced, more technologically advanced models from the Japanese Big Four.
[9] Norton's vertical twin engine that powered the Commando had reached the limit of its development for both road and track by the early 1970s.
[10] The engine design could be traced back to Bert Hopwood's 1947 497 cc (30.3 cu in) Norton Model 7 twin.
[15] At the end of the 1975 season[16] Victor Palomo tested the Challenge at Silverstone on behalf of the Spanish Norton importer JA Rodes[2] with the intention of using the bike for F750.
It also declined a request, sponsored by the RFME (Real Federación Motociclista Española), to supply the Venezuelan Venemotos team.
[15] Croxford was never able to achieve lap times on the Challenge that he had previously managed on the Commando engined John Player Nortons.
This bike may have been a test-bed for the Cosworth technology or possibly a prototype interim model between the Commando and Challenge to reduce initial tooling costs.
The German then sold Scottish Norton enthusiast Ian Sutherland two engines and enough cycle parts to build a complete bike.
It was given two 20 minutes demonstration runs[15] at the August 1981 Donington Park 50th Anniversary meeting[17] by Scottish racer Jock Findlay and racing journalist Alan Cathcart.
[24] Graves intended to build a Battle of the Twins[d] racer using the engine and asked F1 and Motorcycle GP world champion John Surtees to become involved in the project.
[29] Exactweld partners Guy Pearson and John Baldwin had previously worked for Surtees' F1 Team fabricating monocoques.
They also had experience designing and building motorcycle chassis, their Exactweld 250 racer having taken the 1984 European 250cc Championship in the hands of rider Gary Noel.
A single, near-horizontal White Power shock absorber ran from the top of the swinging arm to the rear of the front subframe.
The engine was fitted with 11.7:1 pistons, 40 mm (1.6 in) Amal Mk 2 Concentric carbs with remote floats and Motoplat ignition.
[29] For 1988 the bike was fitted with an experimental mechanical fuel injection developed by Cosworth and produced 120 bhp (89 kW) at 10,500 rpm.
[35] In 1995 it was reported that Triumph Motorcycles Ltd were considering producing a 750 Bonneville sports bike using a trellis frame and the Cosworth twin engine as developed for the Quantel.