Cycle News - Archive Issues - 1990's

n oid-con troll ed duc ts and chambers, altern ately balances or crea tes a differential in pr essu re in va rious p arts of the in ta ke syste m. Ev iden tly th e th e ory being that at low speeds intake velocity th ro ug h the carbu re to rs - es pecially in light of this year's larger bore di ameter isn' t high eno ug h to provide p recise and adequate fu el flow . Hon d a a d d resses this "problem" by slightly p ressurizing th e float cha m ber at speeds und er 12 mph to p rovide more posi tive fuel deli very, thu s im proving low -end power and th ro ttle respon se . At h igh er speeds the air p ressure in the float chambers is balanced with the air flowing through the carb u re to rs - s lig h tl y pre ss u ri z ed because of the ram effect - to main tain accu rate fuel d elivery . The floa t chambers are not the only aspect of the carburetion subject to a ma nipulati on of pressu re. The vacuum chambers, too, get the treatment , balancing the pressure in the vacu u m cha mbe rs with the pressure in the main bores to ensu re correct mixture at all speed s. Th e re ci p ien ts of a ll thi s precisel y con trolled air pressure ar e fou r 38m m (2m m large r th an last year), flat -slid e, sem i-downd raft Keihin CV carburetors . In a d d it ion, th e in take tract h as been straigh tened, sho rtened by 5mm, and the sh ape of the cylinder hea d ports refined to increase volu metric efficiency at high en gine s peed s. With th is in mind, the exh aus t system now has a larger muffler and int erconnectin g tubes bet ween the downpipes to increase midrange power. Recom mended fuel, like all Ho nd as, is regular unlead ed . . That's all well and good and seems rat iona l enough, bu t how d oes it translat e to rea l-world rid ing con d itio ns? Rather we ll, actu ally. In head-to-h ead , roll-on acceleration testing, the new F-3 was noticeably mo re crisp in response to vari atio n in th rottle opening and soundly defeated the previou s iteration of the CBR in ac ce lera t io n - no ma tter th e speed or gear selection mad e. An d select ing those gea rs is ano ther cha nge d e xpe rie nce. Th e rat io jump /rom second to third has been narro wed, and, with the ad dition of need le bearings on the se lec to r shaft, sh ifting is now a smoother expe rience. The linkage offset . is reduced, modifi ed to provid e sho rter th row s an d more p os itive sh if ts . The clutch plates are di fferent this year, .su ppos ed to p ro v id e smoother take-u p. Clutch effort for the cable actuated unit v as light and positive with no evi dence o f ju dd e r . In th e p a st, C BRs have clunked rather lou dly when shifti ng into first gear, even at low rpm, and though improved , it still does so, jus t not quite as mu ch. Extending the balance theme, various mod if ica tions have been made to the sus pe nsion on both ends. The fork is the sa me 41mm conventional Showa u n it used on the F-2 - held by a thicker lower tr ipl e-cla mp - but the 12-step rebound .adjusting valve is now submerged in oil, producin g, Hon d a claims, less aeration d u ring spi ri ted u se . Not a profo u n d cha nge if yo u ar e rid in g on the st ree t, but if you happen to be going racin g, it should keep the dam ping rate more consisten t un der the heavy loa ds encou ntered on the track. The sealing surfaces on the forks tub es are now protected by sma ll stone guard s mounted on the sliders, similar to those used on CBR900RR. Su spen sion tra ve l for the front is unchanged at 5.1 inch es. Th e ratio for the Pro-Lin k rea r sus pension has been changed slightly from las t year to provid e stiffer damping near full comp ressio n, while in the initial part of the travel the ra te wa s d ecr ea s ed gi ve to a more comp liant ride . The shock itself is unchanged, still offering adjus table preload , com pressio n and rebound d am ping, and travel, lik e up fro n t, is unchanged from last year. The fram e is fund am entally unchanged from the F-2. Wh y cha nge a su ccessfu l formula? Of particular note is the news 5-inch-wide rear rim. The bigger rim allows the fitment of a wider tire, a lth ou gh th e CB R sti ll co mes s tock w ith a 160 /60 17incher. Though larger, the cast alumi num rim has undergone a weig h t redu ction of so me 200 g ra m s, d e cre a sin g unsprung weight to aid wh eel control. The s toc k tires a re Z-ra ted Brid gestone Battl eMax radials said to offer the seem ingly contradictory a ttributes of in creased g rip and longer tread life. Time will tell. T o h a n d le the additi ona l stresses likely to be encountered wh en usin g a wider rear tire, the s w in g a r m pi v ot is larger in . diameter at 17mm - up from 15 and now hollow giv ing a slig ht reduction in weight. (Left) A new addition to the CBR600 is the dual-stage ram air-induction system. The small inlets under the headlight pressurize the float chambers at low speeds. Lurking in the shadows is the main intake. Th e fro n t ri m is a 17-inch, cas t alumin um p iece, 3.5-inches wi de, shod wi th a 120/60 ZR17 Bridgesto ne . Bringin g all of these parts to a hal t are larger diameter d ua l-di sc fro nt brakes. The new full y floati ng d iscs are 20mm' large r in diameter an d 1mm thinner than those u sed la st y ea r, an d are crossdrilled for efficien t coo ling . Ho pef u lly the thinner discs won' t mean th at they are more prone to wa rpage . Aluminum dual-piston caliper s are use d . In practice the front brakes p rovid ed excellent feel and fad e-free sto pp ing, w ith very little pressure on the lever. At th e rear, the single disc is the sa me 220m m rot or as that used on the '94 bike, and utili zes a sing le-piston cali per. What does all of this great technology cost? Well, Honda reckons it's wo rth just about $1100 mor e tha n in '94, with the suggested retail price now set at $7299. Availab ility of th e 1995 CBR600 F-3 is slated for ea rly January, 1995. 1-:\ Honda CBR600F·3 Engine liquid-eooled, 599cc in-line four-eylinder Bore x stroke 65x 45.22mm Compression ratio 12 :1 Valve train DOHC, four valves percylinder Carburetion 36mm semi-downdraft flat-slide CV-type Ignition .. .. Computer-controlled digital nansistonzed with electronic advance Transmission .Six-speed Final Drive 0-ringsealed chain Suspension load and 12 -step rebound adjustable Front .41mm stepless pre cartridge-type fork with 5.1 inchesof travel Rear Pro-Unk with seven-step preload, . justable steplesscompression- and rebound-ad damper with gas-eharged reservoir with 4.3inches oftravel Brakes Front. 296mmdual disc with twin-pis calipers ton Rear 220mmsingle-pistondisc Wheels Front 3.50' 17"U"section six-spoke cast aluminum Rear 5.00-17"U" section six-spoke castaluminum TIres Front 120/60 ZR17 Rear 160/60 ZR1 7 Wheelbase 55.3inches Seat Height 31.9 inches Fuel Capacity 4.5gallons DryWeight 407.9poun ds Suggested retail price $7299 . ~ \0 ,..... l-< Q) E Q) :> o Z 23

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