Honda CB350/4

Petit Four

Old Bike Australasia - - CONTENTS - Story Peter Laverty and Tony Sculpher Photos Tony Sculpher and Jim Scaysbrook

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.

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