The P92 pro­to­type: What might have been

Classic Bike (UK) - - Bsa B50 (and Related Singles) -

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.

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