But the RC173 had little in common, apart from the brand on the tank, with the machine announced in July 1972. At first creating widespread interest, the 350 being visually similar to the popular CB500 four, enthusiasm waned somewhat as the first test rides took place. One magazine tester lamented, “Honda’s new 350cc four is easily the heaviest, most expensive thing in its displacement class, and a list of others capable of going a standing-start quarter quicker than the Honda would be a lot longer tally of those that won’t…Honda shouldn’t even have contemplated building a four-cylinder 350…All they can hope to do with the 350 Four is lure buyers away from their own 350 twin.” So, overweight, over priced and under performing? Sounds like a recipe for disaster.
Looking back 46 years, it is true that the 350 Four was anything but a showroom success, and that its twin-cylinder counterpart continued to rein as the largest-selling motorcycle in the USA for several more years. But today, we perhaps see the Four for was it is, or rather how (and why) it was conceived. In the face of increasing four-stroke opposition from the other Japanese manufacturers, Honda wished to demonstrate in no uncertain terms that they were still king of the camshaft brigade. When they put their mind to it, they could make anything, and the 350 Four was the smallest capacity four cylinder motorcycle ever to enter mass production. And rather than satisfy a known market, why not create one? That last question was answered by the model’s embarrassingly brief production run of less than two years. Curiously, the model was never released in the UK, but given the sales figures from other world markets, it probably wouldn’t have worked there either. The smallest Four used an engine that had visual similarities to the CB500. Against current thinking, it was under-square, with a bore and stroke of 47mm x 50mm, and a 9.3:1 compression ratio. The familiar chain drives the single camshaft, but there is no external adjustment for that chain. The crankshaft ran in five plain bearings, with a Morse chain primary drive running from the centre of the crank to the clutch. Four 20mm Keihin carburettors fed the mixture, which exited via four separate exhaust pipes with tapered megaphone style mufflers. Those components, like the ones found on big brothers, had a fairly short life before surrendering to corrosion, collapse, and replacement, usually with an after-market four-into-one system.
Like its siblings, the smallest Four stuck with points rather than move to the new-for-the era CDI systems. By allowing each coil to lose a spark on the exhaust stroke, there was no need for a distributor to send the spark to the correct plug. Unlike the 500, which used a duplex cradle frame, that on the 350 was a single down tube affair, which split into a loop at the bottom to allow the oil filter to poke through. Up front sat a 254mm single disc brake, which by all accounts worked very well, with a single-sided hydraulic pad working against a fixed pad via a flexibly mounted caliper, as on the other ‘fours’. A major complaint on the CB500 was dramatic loss of efficiency in the wet, and to this end the 350 was fitted with a plastic shield at the rear of the rotor to prevent water running onto the disc. A 152mm drum provided the rear stopping. The suspension was fairly typical of the era, with a telescopic front fork with one-way damping, and a pair of rear suspension units that seemed devoid of efficient damping. All the bodywork on the 350 was unique to the model. Total sales world-wide amounted to under 80,000. Compared to other ‘fours’, the CB350F is quiet, almost disturbingly so. Air reaches the carburettors via twin air boxes with a rubber inlet pipe under the seat, and there is obviously plenty of baffling inside the mufflers. Testers complained that the seat was too hard, and that the footrests were a bit too far forward – something that may have been alleviated by the use of lower handlebars than the semi highrise style fitted as standard. But there were many nice touches, such as the lockable seat that kept the tools safe from prying hands, and the incorporated helmet lock. Both the air filter and battery were easy to service. “Smooth” was the most common descriptive used of the 350 Four. Not less a figure than Soichiro Honda himself declared it to be “the finest, smoothest Honda ever built.” It certainly had an appetite for revs, being red-lined at 10,000, but with minimal power below 5,000 rpm. There was also a vibration period between 5,500 and 6,000 rpm, which is precisely where most time is spent in traffic, causing the mirrors to vibrate with associated loss of rear vision.
The 350 Four did not go on sale in Australia until early 1973, and at $1025 it had a hefty price penalty compared to other 350s, such as the RD350 Yamaha at $859. But the newest four did offer a high degree of sophistication, plus the kudos – perceived or not – of those four gleaming pipes. It’s true that few found homes here, and the overriding reason for that was the competition the Four suffered from its own brother, the 325cc CB350 twin, which was a damned good bike, lighter, nearly $200 cheaper, and quicker. The CB350 Four shared virtually nothing with the CB500 (which shared virtually nothing with the CB750) so it was expensive to tool up for, and with such a short production run, almost certainly unprofitable. In most schools of thought, apart from Honda’s, interchangeability of parts between models, and shared manufacturing platforms, were the way to go –the CB250/350 twins exemplified this thinking. But perhaps the shortcomings of the 350 spawned what is generally held to be one of Honda’s greatest models of the ‘seventies – the handsome, fast and light CB400F. Now that’s quite a legacy.
Famous forebear – Mike Hailwood on the factory RC173.
Moto Guzzi showed their take on the four-cylinder 350 at the 1974 Cologne Motor Cycle Show.