The P92 prototype: What might have been
By 1974 the management at increasingly cashstrapped NVT were desperate to come up with new models. Knocking up a ‘parts-bin special’ like the P92 prototype made sense. It might have made a fine motorcycle, too, had it made it to production. The P92 is the odd man out of our three B50based test bikes. It’s a genuine factory prototype, with all the innovation that implies – but also the raw, unfinished compromises necessary to get a bike on the road to prove whether a concept would work or not. You can’t quite judge it in the same way.
The history of the P92 is a little confusing and there seems to be no hard consensus on the number of prototype machines built. Three or four would be a reasonable guess, with two known to have been built at BSA’S Kitts Green R&D facility and a third (probably our test bike, kindly provided by the National Motorcycle Museum) at Wolverhampton.
What is not in doubt is that the bike – created by a team headed by former Triumph engineer Brian Jones – was essentially a fusion of the frame intended for the BSA Fury/triumph Bandit ohc 350 and a modified BSA B50 engine. The engine was canted forward in the frame, both to mimic the style of the Commando and to allow the installation of an external crossover shaft for the gearchange under the rear of the gearbox – a cheaper alternative to redesigning the engine to accommodate an internal crossover arrangement. A few of the other surviving prototypes also have interrupted finning on the barrels – an affectation adopted later on CCMS.
Apparently all the prototypes were slightly different. Various modifications were incorporated to the B50-based engines. ‘Our’ bike from the NMM features a one-into-two-exhaust system with Commando-style silencers, four-stud 1971 pattern Bsa/triumph forks and conical hubs.
But despite the pragmatic mixture of available parts, the look of the P92 hangs together remarkably well. And the concept of a slim, light and punchy big single – but without the jack-hammer vibes normally associated with fast, big-bore one-lungers – seems almost ahead of its time for 1974.
In the end, it didn’t matter how good the P92 could have been. The demise of NVT meant the project would remain just that – a project. But today we’ve got Rick on hand to assess what might have been with a test ride on the NMM P92. “The mixture of BSA, Triumph and Norton components reflects the reality of a declining industry desperately trying to create a winning dish from a handful of leftovers.
“On the test machine a problem with the Isolastics made the handling dubious and the engine no smoother than the other bikes, but it’s reasonable to assume that the Iso-b50 would steer very well and be smooth at all speeds. It’s comfortable, with a relatively modern riding position and left-side gearchange. Effected using a cross-shaft and linkage, it doesn’t dictate footrest position as on a T140 allowing a pleasantly rear-set position. It works well apart from a tendency to jump out of top (probably gear wear rather than design flaw) but owner failure to lubricate the cross-shaft would cause problems. “The engine is as lively as Tony’s B50MX and you can see the thinking behind presenting it in a vibefree, sharp-handling, stylish, lightweight sports bike. Tony Howard certainly approves. ‘I think this bike could have been a success,’ he says with enthusiasm, ‘It looked great. It would have needed an electric starter, but they could have tacked one neatly on top of the gearbox.’ I’d suggest a front disc, too, but starting is the big issue. BSA made kickover easier by lowering internal gearing at the expense of cranking speed. I struggled until I remembered Velocettes are the same. Adopting Velo starting drill, the B50 fired up easily; but ’70s riders weaned on a CB250K4 were unlikely to welcome arcane starting rituals.
“The Iso-b50 is more of a contender than I expected, the bike is attractive and ahead of its time – thanks largely to a frame design that didn’t appear on Japanese bikes for another decade, but it was ahead in another way. The buying public wasn’t ready to revisit the single for at least another decade, as Yamaha and Suzuki were soon to discover.