Honda re­de­fines the 250

There was very lit­tle wrong with the C72 Honda that ap­peared in 1959 – “a ma­chine of almost un­be­liev­able so­phis­ti­ca­tion” ac­cord­ing to the Bri­tish press – but what fol­lowed was a whole lot bet­ter.

Old Bike Australasia - - FRONT PAGE - Story and pho­tos Jim Scays­brook His­tor­i­cal pho­tos Keith Ward

In de­sign­ing the CB72 (and its big­ger-bore brother, the 305cc CB77), Honda’s en­gi­neers con­sid­ered the func­tion­al­ity of ev­ery ex­ist­ing com­po­nent be­fore de­cid­ing on the fi­nal spec­i­fi­ca­tion.

La­belled “the star of the show” when it made its Euro­pean de­but at the Am­s­ter­dam Show, the C72 was the log­i­cal de­riv­a­tive of the C70 Dream from 1957. The C70, with its pressed steel frame, forks, swing­ing arm and mud­guards had been rarely seen in the west, Honda ex­port­ing just 285 ma­chines that year, mainly to South East Asia. The C70 was up­dated in 1958 with the ad­di­tion of an elec­tric starter, and in C71 form, ar­rived in Bri­tain in 1958 equipped with 6 volt electrics. The new C72, with 12 volt electrics, the C92 Benly 125 and the C100 step-through, formed the ba­sis of Honda’s ex­port drive into Europe and USA, but although the spec­i­fi­ca­tion of all three was bril­liant for the time, the styling still po­larised opin­ion. And so it was that the CB72 came into be­ing – in­cor­po­rat­ing the ex­cel­lent SOHC Twin cylin­der 250cc en­gine, but with more con­ven­tional styling, in­clud­ing a tubu­lar steel frame. The orig­i­nal C70 en­gine re­drew the bat­tle lines in the quar­ter litre class. De­vel­op­ment of the Euro­pean 250s from the likes of Moto Guzzi, MV Agusta, NSU, Maico and the East­ern Bloc CZs and Jawas had largely stalled as cheap cars be­came more read­ily avail­able. In the case of NSU and DKW, they sim­ply ceased mak­ing mo­tor­cy­cles al­to­gether. In Eng­land, BSA, AJS/Match­less and Ariel had ven­er­a­ble 250 sin­gles, Ariel would soon have the twin-cylin­der two-stroke Ar­row, and Nor­ton fid­dled about with their Ju­bilee twin, but be­neath the sur­face, there was lit­tle new. And that’s largely be­cause the bean coun­ters had de­clared the class all-but dead, and not worth the in­vest­ment for tooling to pro­duce new mod­els. Not so the Ja­panese. Hav­ing started with tid­dlers, the only way was up, and their home mar­ket was a fer­tile one for such ma­chines. The C70’s en­gine was – uniquely for the pe­riod – all al­loy, with hor­i­zon­tally split crankcases and dry sump lu­bri­ca­tion. Vi­tally, the elec­tri­cal sys­tem of the lit­tle twin was well thought out and re­li­able – almost the com­plete an­tithe­sis of most of its ri­vals. But there was still the mat­ter of the very Ja­panese styling, which at the time was char­ac­terised by squared off pan­els and sharply an­gu­lar de­sign.

In de­sign­ing the CB72 (and its big­ger-bore brother, the 305cc CB77), Honda’s en­gi­neers con­sid­ered the func­tion­al­ity of ev­ery ex­ist­ing com­po­nent be­fore de­cid­ing on the fi­nal spec­i­fi­ca­tion. By the time the model went into pro­duc­tion, it shared vir­tu­ally noth­ing with the C70 line apart from a gen­eral sim­i­lar­ity in the pow­er­plant. The CB72 en­gine be­came wet sump, with a 180º crank­shaft in­stead of 360º - the crank run­ning on four bear­ings, outer ball bear­ings and roller in­ners. The sin­gle over­head camshaft was chain-driven from the cen­tre of the crank­shaft. Alu­minium al­loy was still used top to bot­tom, but inside the cylin­der head, the com­bus­tion cham­ber em­ployed a cast iron “skull” as used on the fac­tory’s highly suc­cess­ful rac­ers, with the valve seats cut into the skull. A fairly high 10.0:1 com­pres­sion ra­tio tested the qual­ity of the fuel of the day, and twin 24mm Kei­hin car­bu­ret­tors fed the mix­ture via two pa­per air fil­ter el­e­ments. A four-speed gear­box, nat­u­rally built in­unit with the en­gine and driven via a sin­gle-row chain from the left side of the en­gine, should have been quite ad­e­quate but due to an ex­tremely odd choice of ra­tios, was per­haps the weak point of the whole de­sign. First gear, at 18.63:1 was ex­tremely low, with a wide gap to the 11.10 sec­ond gear. This meant sec­ond was of­ten too tall for use in traf­fic, but bot­tom was too low. Also, when chang­ing back through the gears, shift­ing from sec­ond to first almost threw the rider over the han­dle­bars. A sim­i­lar sit­u­a­tion oc­curred with the later 4-speed CB450, but this was cured by adding a fifth ra­tio be­tween first and sec­ond – a rem­edy that was never ap­plied to the CB72. Nowa­days, NOVA in Bri­tain of­fer a five-speed trans­mis­sion for the CB72/77 that goes straight in and re­port­edly trans­forms the per­for­mance. Gone was much of the pressed steel, with a tubu­lar steel frame and swing­ing arm. The frame was of the

spine type, us­ing the en­gine/gear­box as a fully stressed mem­ber. The old lead­ing link forks were also dis­pensed with in favour of con­ven­tional look­ing tele­scop­ics, with sim­i­lar Brit-styled spring/dampers, ad­justable for spring pre-load, at the rear. Mud­guards were very Bri­tish in ap­pear­ance; the front a neat ‘three inch’ blade with twin stays, and the rear a stubby but ad­e­quate job with a screwed on hor­i­zon­tal mud­flap. The C70 seat de­sign, with its fea­tured curves and con­tours, also gave way to a much more con­ven­tional, flat-topped style, still with a cen­tre grab-strap and a neat lower chrome trim strip.

The flat-sided fuel tank set a styling trend that Honda would follow for the next few years in a va­ri­ety of mod­els, with screwed on chrome side pan­els and ex­ten­sive rub­ber knee pads. A large head­lamp with 35/35w il­lu­mi­na­tion sat up front, with the com­bined speedo tacho in­stru­ment set into a cowl­ing in­cor­po­rated within the head­lamp shell. Although sim­i­lar to the ear­lier items, the CB72’s brakes were all-new; both front and rear be­ing 8-inch twin lead­ing shoe. Both the CB72 and CB77 were avail­able in three ba­sic colours; black, red or blue, with sil­ver for the mud­guards and air fil­ter side cov­ers. One Bri­tish road test de­scribed the CB72 as “a dif­fi­cult bike to ride; no ma­chine for the novice. To be kept go­ing quickly on an or­di­nary road, the rider needs to keep the rev-counter nee­dle point­ing be­tween 7,000 and 8,000 rpm, and to change gear much more of­ten than usual.” The fuel con­sump­tion (62 mpg) also came in for some crit­i­cism, but praise was univer­sal for the han­dling and brak­ing. Later, Honda in­tro­duced a 360º crank­shaft for the CB72, this model were known as Type 2, and iden­ti­fied as such by the in­scrip­tion on the right side camshaft cover. Although listed as hav­ing the same power out­put, the Type 2 pro­duced a wider spread of power with in­creased torque. As well as be­ing sold ex­ten­sively in the US, the Type 2 en­gines were fit­ted to Po­lice model CB72s (the CYP72) sold through Asia, pre­sum­ably for their abil­ity to han­dle low speed traf­fic bet­ter.

The need for speed

Honda ob­vi­ously saw rac­ing po­ten­tial in the CB72 (or at least, café racer hot-up), as pro­vi­sion was made to eas­ily con­vert the stan­dard footrest/brake/gear lever to ‘rear-set’ con­fig­u­ra­tion. A large cast-al­loy bracket on each side acted as the muf­fler mount­ing point and con­tained a cen­tral boss to move the footrest 60mm to the rear, and both the rear brake and gear lever link­ages could be sub­sti­tuted for longer ver­sions to suit. This footrest/lever set up meant that there was no room for the kick starter to ro­tate in the con­ven­tional fash­ion, so it was a case of push­ing the lever for­wards – a tech­nique not that dif­fi­cult to master but for­tu­nately not called for of­ten due to the re­li­a­bil­ity of the elec­tric starter. Honda was rid­ing a wave of rac­ing suc­cess in the early 1960s, and was nat­u­rally keen to ex­ploit this suc­cess in its road mod­els. The CB72 could be had, in Bri­tain at least, with flat han­dle­bars, big­ger bore Kei­hin car­bu­ret­tors, a slightly warmer camshaft and the rear-sets. A num­ber of ac­ces­sory firms of­fered rac­ing-style seats. The fac­tory even pro­duced a very limited num­ber of gen­uine rac­ing CB72s, code named CYB, which looked sim­i­lar to the RC61 from a dis­tance, with the same elon­gated fuel tank and seat. In fact, they em­ployed more than 100 dif­fer­ent parts to the road bike, in­clud­ing al­loy rims, footrests that could be mounted in three dif­fer­ent po­si­tions, clip-on han­dle­bars with ca­bles to suit, two styles of re­verse cone mega­phone in dif­fer­ent ta­pers, al­loy mud­guards, two-way damped rear shock ab­sorbers and lots of other smaller bits and pieces. Inside the en­gine was a rac­ing camshaft, valve springs, higher-spec pri­mary chain, close ra­tio four-speed gear clus­ter (with a fivespeed also listed), rac­ing car­bu­ret­tors and dif­fer­ent cast­ings to re­place the sta­tor and starter mo­tor. The CYB con­ver­sion was ac­tu­ally mar­keted as a kit in sev­eral forms, from ba­sic to a com­plete set up. From all ac­counts, the rac­ing CB72s were not par­tic­u­larly suc­cess­ful, although they were ca­pa­ble of run­ning at 11 – 12,000 rpm. Prob­lems with the camshaft drive, man­i­fest­ing it­self in bro­ken cam chains (usu­ally the con­nect­ing link) plagued the mod­els, and it was only when “Pos” Yoshimura worked his magic inside the en­gine that a de­gree of suc­cess was achieved. A hand­ful of CR72 and CR77 rac­ers were sold to se­lected rid­ers, in­clud­ing Ir­ish­man Tommy Robb and South African Bruce Beale. Th­ese used gear drive to twin over­head camshafts, with one-piece four valve heads, six speed gear­boxes and a dry clutch. The cylin­ders were sep­a­rate, with the camshaft drive gears be­tween them in a com­part­ment sealed

with a rub­ber gas­ket. The 54mm x 54mm 250 pro­duced 42 horse­power at 12,000 rpm, while the 60mm x 54mm 305 de­vel­oped 46 hp at 11,000 rpm. Robb’s CR77 was timed at the TT at 134 mph – 2 mph faster than Mike Hail­wood’s works 350 MV Agusta. In Aus­tralia, the CB72 quickly be­came the weapon of choice for the boom­ing Pro­duc­tion Rac­ing scene. When Light­weight (250cc) and Un­lim­ited Pro­duc­tion races were in­tro­duced at Bathurst in 1962 (after years of con­cen­trated lob­by­ing for ‘club­men’ who had lit­tle hope of get­ting onto the grid oth­er­wise), the CB72 dom­i­nated the en­try and took the first three places ; Gary Gates win­ning from Vic­to­ri­ans Ray Moloney and Ron Bridge­man. Maloney won in 1963, and it was Terry Den­nehy’s turn in 1964, but after that, the two stroke bri­gade, in the shape of Yamaha’s YDS-3 took over, and this pretty much mir­rored the for­tunes of the CB72 world wide. The CB72 was un­der threat from two strokes, not just on the track, but for road sales, Honda wag­ing a sin­gle handed war against the Yamaha YDS-3, the six-speed Suzuki T20, and Kawasaki’s new A1 dis­c­valve twin. Honda main­tained, quite cor­rectly, that the majority of the sales in this cat­e­gory (and in 350cc) were to be had in the com­muter, not the sports seg­ment. Sales of the CB72 were in steep de­cline by 1966, and the fol­low­ing year Honda showed its re­place­ment, the five-speed CB250 with a to­tally new pow­er­plant. The new model was slightly heav­ier, slower, but a more re­fined pack­age, and in 350cc form as the CB350, be­came the high­est sell­ing full sized motorcycle in the world, thanks to the mas­sive take up in USA.

In the sad­dle

In mid win­ter 2014, I was for­tu­nate to be loaned the fea­tured CB72 by owner Richard Steain, for use in the an­nual Deben­ham Rally in the NSW South­ern High­lands. I ac­tu­ally owned and re­stored a CB72 my­self many years ago, but when I put the ma­chine on the road I found it less than won­der­ful. The main prob­lem was the cu­ri­ous spac­ing of the gear­box ra­tios, as pre­vi­ously men­tioned. In Syd­ney traf­fic, it was also a bit of a chore keep­ing the en­gine buzzing in its com­fort zone, but the han­dling was very good, as were the brakes. Twenty years after that ex­pe­ri­ence, the day blast­ing be­tween Bowral, Mit­tagong and other small towns in one of the pret­ti­est re­gions of NSW was an al­to­gether dif­fer­ent ex­pe­ri­ence. Richard Steain is a man highly versed in the smaller Ja­panese bikes, and (with twin brother John) was a for­mi­da­ble tal­ent on the race tracks. His tackle then was mainly T20 and T250 Suzukis in the rough and tum­ble world of Light­weight Pro­duc­tion rac­ing, but in lat­ter years he has col­lected and re­stored a nice line up of Ja­panese bikes, mainly Hon­das, of var­i­ous sizes. His CB72 is not pris­tine, but it is very well put to­gether and is a joy to ride. On the open roads, I didn’t even mind the gear ra­tios too much – I just rev­elled in the lit­tle ma­chine’s agility to swoop through the twists and turns. I even re­marked to John that the han­dling was ‘Ve­lo­cette-like” – the high­est praise I can be­stow! There is in­creas­ing em­pha­sis on the smaller Ja­panese bikes as rally trans­port, and with good rea­son. They’re light, re­spon­sive, han­dle well and re­quire min­i­mal main­te­nance. The CB72, with its push-but­ton start­ing, is an ex­cel­lent choice and prices are still rea­son­able.

Get­ting dirty (but only a lit­tle)

USA quickly warmed to the CB72, (par­tic­u­larly after Elvis Pres­ley hit the screens in the 1964 movie Roustabout where he rode a CB77) but be­came much more en­thu­si­as­tic to the con­cept with the re­lease of the ‘street scram­bler ‘ CL72/CL77. Th­ese mod­els used the ba­sic CB72 en­gine pack­age, but the frame was beefed up with the in­clu­sion of a sin­gle front down­tube, split­ting into a cra­dle un­der the en­gine. This mod ne­ces­si­tated the re­moval of the elec­tric starter, which on the CB72 was mounted at the front of the en­gine. This re­ally did not present a prob­lem, as the en­gine was eas­ily kick started, es­pe­cially as the kick starter now ro­tated in the tra­di­tional pat­tern, rather than the ‘for­ward’ mo­tion of the CB72. Wheels on the CL mod­els grew from 18-inch to 19, and a hy­draulic steer­ing damper was fit­ted as stan­dard. Per­haps in search of more low-down torque, the 24mm Kei­hin carbs were re­placed by 22mm Bil­iaths. When the 305cc CL77 came on board for 1965 (in the US), it sported 26mm Kei­hin carbs. The twin-lead­ing shoe brake plates be­came sin­gle lead­ing shoe front and rear on the CLs. In re­al­ity, th­ese street scram­blers were bet­ter at boule­vard pos­ing than any form of rough stuff, but the styling, with the high-mounted ex­haust sys­tem on the left pro­tected by an elab­o­rate heat shield, the small fuel tank, high han­dle­bars and ab­bre­vi­ated mud­guards cer­tainly cap­tured the imag­i­na­tion of the buy­ing pub­lic and the CLs sold in big num­bers. Late in the pro­duc­tion run, the CL was re­leased with a 360º fir­ing or­der. In USA, sales of the CL77 far out­stripped that of the 250 and both the CL mod­els en­joyed good sales in Ja­pan.

A red 1966 model CB72 re­stored by Steve Ashke­nazi. A blue CB72 re­stored byCamp­bell Clas­sics.

BE­LOW Al­lan Os­borne at Calder in Fe­bru­ary 1962 on a CB72 that has been race-mod­i­fied with clip-ons, rear sets, mega­phone ex­hausts and with the sta­tor and other weighty bits re­moved. LEFT Orig­i­nal Honda brochure show­ing the three colour op­tions for the CB77.

At Dar­ley in June 1962, P. Mills (10) on a new CB72 leans on Nor­ton-mounted P. Mor­gan.

Top Vic­to­rian rider Ray Moloney, win­ner at Bathurst in 1963, on his brand newCB72 at Dar­ley in June 1962.

Slab-sided fuel tank with tra­di­tional knee rub­bers.

TOP A dis­tinc­tive and at­trac­tive en­gine de­sign – Laverda cer­tainly thought so! ABOVE 24mm Kei­hin car­bu­ret­tors. BE­LOW Type 1 on the camshaft cov­ers de­notes the 180º crank­shaft en­gine. BOT­TOM Starter mo­tor sits neatly at the front of the en­gine on the CB72, but was elim­i­nated on CL mod­els. BE­LOW RIGHT Al­loy brack­ets on both sides have a cen­tre boss for rear-mount­ing footrests. BOT­TOM RIGHT Typ­i­cally ‘six­ties Ja­panese, the head­light-mounted in­stru­ment com­bines the tacho and speedo.

Newspapers in English

Newspapers from Australia

© PressReader. All rights reserved.