Cycle News - Archive Issues - 1970's

can stand. Abrupt throttle transitions from fully closed to wide open at low engine speeds don't produce lurching, bogging or hesitation. Unlike the CV carburetors on many other machines , the CBX's Keihins are possible to control precisely with the twist grip. An accelerator pump on the third carburetor body feeds the six intakes through spray nozzles, adding to th e responsiveness of the engine. The transmission has the finest feel and action the magazine men have ever experienced in a street bik e. Light and positive with a short throw, the transmission acts as if it were custom built - which it was. The clutch, too , has ideal qualities. A perfect engagement point, controllable action ' and apparant immunity to the most severe treatment. It's as if Honda , playing an industrial Santa , asked the rider what sort of transmission and clutch he 'd like for Christmas; and having gathered the requests, went off and built th e perfect power train . Racetrack handling is less desirable. Even this special CBX is far from p e rfect when run hard on t h e ' ra cetrack, even on its sm a llish street tires . The bike weighs 600 pounds with a full tank of gas . and never lets the rider forget that fact. The CBX must be pushed down int o fast turns and lifted back up out of them , wrestled from side-to-side in left-right ser ies of corners. A slow , steady, disconcerting oscillation in Willow's wi d e- op e n eighth turn makes the rider think that the co n n ec ti o n between the front wheel and the rear wheel isn't quite rigid. Running the CBX into tu rn eight "on the gas " is unsettling at best: • Then, too . the CB X gets excited if the rear brake isn't handled with great care on bumpy entrances to slow turns. Like the rear brake on the GS750 Suzu ki, the CBX's 295mm rear disc will lock and send the wheel skipping out of control. Just like the frames used on the "famous for wobbling" Honda 250 and 300cc six-cylinder r.rand Prix road racers in the 1960s, the CBX frame doesn't have front downtubes . Instead , the frame backbone section bolts to the cylinder head in three places , using steel mount plates in the fr ont. The rearward frame section bolts to the crankshaft/transmission cases. When the engine was disassembled for internal photography a few days later , scuff and gall marks were discovered on the top engine mount plates , the result of the engine 'weigh t (235 pounds withou t oil) overcoming the engine mount bolt torque in high speed cornering. Shoichiro Irimajiri , 37 , designed the mid-sixties six-cylinder ra cers and the new CBX . To hold down the weight of the complicated new ma chin e . Irimajiri shaved off ounces wherever he could. The fork sliders were turned down in thickness in low stress areas, and the swingarm and pivot mount bolt were kept small and light. Plastic bushings are used on the swingarm itself, in contrast to the much better needle roller bearings used in Suzuki GS series swingarms. Those facts , plus the use of shocks which quickly fade when the bulky CBX is herded around the racetrack, severely limit the big Honda's racebike potential. Un less extensive frame and su sp ension modifications are made , any CBX raced with sticky slick tires sh ou ld set new records for evil h a nd ling . That 's a shame, because as it sits , the CBX makes more horsepower than is evident from riding around the ex p a nse of a racetrack : Honda 's e ng in eer s, in sp it e of several concessions made to make th e CBX a more comfortable street bike, claim 10 3 horsepower at the crankshaft. Indeed. a few days after it was first rid den by the journalists at Willow Springs, the C BX produced 85.6 horsepower on a rear-wheel dy n am om eter in Los Angeles , the most ever recorded for a street bike at that facility. The same dyno is used as the U.S. magazine standard for measuring test bike power. Also a few days following the CBX's racetrack debut , the big Honda was tak en to a dragstrip . In the midst of a r ainstorm , the Honda burned off a best standing start quarter mile ela psed time of 11.65 with a terminal speed of 116 mph after three runs on slippery pavement. A month later, after the CBX had re tu rned to Japan for its introdu ction to U .S. dealers, th e six again made the trip to California and took a shot at a dry dragstrip . In 11 runs , theCBX reached a elapsed time of 11.55 with a terminal speed of 117 .5 mph. The best time a production XSll Yamaha has managed on the same d ragstrip stands at 11.73; a Suzuki GSlOO, 11.81. If prototypes counts, then the C BX is the m ost powerful, quickest and fastest street bike to ever come out of Japan . According to Irimajiri , racing pipes, carburetors, camshafts and pistons will give the CBX a maximum of 140 horsepower at the crankshaft , using stock displacement. And according to the best estimate of a leading J a panese aftermarket racing parts manufacturer in Los Angeles, an overbored CBX could reasonably be expected to produce ove r 15 ~ horsepower with enough reliability to finish long road races . Along with power p otential , the CB X also has exc ellent b ra kes. Unlike the recent trend, the Honda's twin 276mm front discs don 't demand an ultra strong pull at the lever for hard braking . Instead, the front brake lever has more travel and requires less force for maximum brakingpower. It's the kind of lever action which can put a panic-stricken novice on his head in a hurry, but which affords an expert excellent control and feel , and wh ich makes working the throttle for downshifts while braking much eas ier . A transverse six is by its nature wide , yet the CBX has good ground clearance for cornering . The engine is j ust over 23 wide - a bout two inches wider than a CB750 four - in spite of its wall-to-wall cyl inders. That's because the alternator and transistorized ignition , mounted on the crankshaft ends of conventional multis , are driven b y a jackshaft located behind and above the CB X 's crankshaft. A 34mm Hy-Vo chain drives the ja cksh aft from the m iddle of 00 ~ W Six cylinders. 1047cc. Double dual overhead cams. Twenty-four valves. Six 28mm constant velocity carbs. with an acce lerator pump. The CBX is like no other street motorcycle ever seen. 7

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