Thursday, 30 July 2015

Honda C90 and C92 Benly 125



Honda's early four-stroke twins were exceptionally advanced for their era and reflected the progress being made in production manufacturing back at the factory. A couple of interesting examples go under the hammer at auction this autumn...
Early Honda motorcycles of the 1950s were largely dismissed as irrelevant by the UK motorcycling press and the man in the street, and indeed they suffered from a variety of engineering issues and teething troubles. But the journalists, at least, took notice of the Benly when it arrived to herald the start of the Swinging Sixties. The Motor Cycle said: 'any lingering notion that Japanese machines are shoddy imitations of West European designs should have been buried several years ago. If it has not, the Honda Benly gives the answer. The bold and intriguing concept of a 125cc overhead-camshaft roadster twin peaking at 9500rpm makes a mockery of a charge of imitation.'
To be fair, the single-cylinder Dreams shared many characteristics with NSU machines, and the twins similarly adopted some of NSU's more successful features. However, Honda produced a motorcycle with its own distinct merits. 'The Benly's finish and excellent engineering are not only far from shoddy but comparable with the world's best.'
Notice they didn't mention the ungainly (OK, ugly) styling. Still grounds for some improvement, but Honda had come a long way in a very short space of time…
Honda introduced its first parallel twin - the 250cc C70 - in 1957. Although the crankshaft was of the 360-degree type familiar to Britbike owners, with its pistons rising and falling in union, the Honda differed from the traditional British twin by building the gearbox and engine in unit, having an horizontally split crankcase, and utilising chain-driven overhead cams rather than pushrod operated overhead valves. The C70 model was made possible in part by an advanced, high-precision machining table which could be used to manufacture multiple models - the Honda Universal Machine.
Rowena calls them ugly... 1959 Honda 125cc C90 Benly 2
The HUM was far more flexible and adaptable than conventional machining tables and paved the way for Honda to adopt a modular approach to their motorcycle manufacture. Honda also claim that the HUM 'achieved a superior degree of accuracy' in 'a remarkable set-up time of just five minutes.' Six HUMs were commissioned and played a vital role in bringing the Dream C70 and Benly C90 to the market - just as Honda themselves became Japan's largest motorcycle manufacturer.
Instead of adopting earlier working practices where the production line consisted of many individual stages, broken down to be as simple as possible, Honda combined several stages into what they called 'multi-directional simultaneous processing.' This integrated several operations, shortened the length of the production line and eventually led to the dedicated, four-direction horizontal turning machine developed for the Benly C90.
But I think they have a certain charm. 1959 Honda 125cc C90 Benly 2. Note distributer on end of cam cover.
The first 125 Benly twins - the C90 tourer and CB90 sports - appeared in 1958 and were swiftly superseded by the almost identical C92 and CB92 which kept the originals' 41mm by 44mm layout. The engine ran at the giddy heights of 8.3:1 compression; utilised two ball main bearings and caged roller big end bearings, and was fed by a single Keihin carb, with wet sump lubrication. Drive was transmitted initially by helical gears through a wet, multiplate clutch to a four-speed gearbox and by a drive chain (tucked away in a full enclosure) to the rear wheel. Ignition was handled by coil with auto-advance.
Braking from the single-leading shoe drums wasn't particularly effective, and the brake had a considerable mass to cope with - 350lb for a 125 would have felt very heavy for a British rider more used to a Bantamweight BSA. UK riders also criticised the Benly's handling, under-damped suspension and its lack of low-down torque - the revvy Honda engine was entirely new territory for motorcyclists used to cruising at 4000rpm.
Funky bars, funky mirror... 1964 Honda 125cc C92 Benly
The C92s dropped the previous models' distributor-type ignition points housing, but all the Benly 125s came with the somewhat clunky styling which typified Oriental machines of the period - square headlamp, pressed steel leading link front suspension, and chunky mudguards.
Even with their compromised appearance, the arrival of these unusual lightweights caused a sensation. Never before had a small capacity 125 been manufactured as a twin, and not just any old twin but one equipped with a four-stroke OHC engine that could rev safely to 10,000rpm and deliver a substantial 11.5bhp. To cap it all, the Benly was also fitted with an electric starter and flashing indicators. And it was cheap, leading The Motor Cycle to declare: 'its above-average road performance goes hand in hand with quietness, cleanliness, economy and tirelessness.'
Those superlatives translated to real-life cruising of around 50 to 55mph with a flat-out top speed of over 65mph. Fuel economy was typically around 85mpg; if you stuck to 30mph then 110mpg was possible. Slightly better, dare one say it, than a Bantam. But the BSA was almost infinitely rebuildable while - as time would tell - the Benly twins proved rather less durable in the long run.
Funky pillion seat... 1964 Honda 125cc C92 Benly
The twin-carb CB92 Super Sports of 1959 was rather more sporty, providing 15bhp at 10,500rpm. It even looked the part, with a red saddle - a definite promise of performance… underlined by Honda's first appearance at the Isle of Man TT races where they managed sixth, seventh, eighth and eleventh place in the 125 race.
The very first 125 Benlys aren't something you stumble across every day in the small ads. A collection of Japanese classics is being auctioned by Bonhams at the Stafford Show in October 2013, and they list a couple of examples. One is a 1959 C90: 'a remarkably complete and original example' which is a 'rare survivor and would make an excellent restoration prospect. The exhausts are rusty, but this is only surface tarnish and nothing that a specialist chrome plating company could not address. We are advised that the engine turns over freely. In short: this is one of the rarest and most complete Honda motorcycles of its type we have ever seen.'