Cycle News - Archive Issues - 1980's

the cran kca se reed -valve i nd uc tion syst em a nd si ngle-cran ks h a ft V-4 des ign , H RC widened th e incl ud ed angl e between th e p ai rs o f cyli nders fro m gO-degrees to 112 - the same as on their ol d V-3 500 tr iple. T h is permitted the pair of twi n 36m m choke s i ngle-body Keihin carbs (34m m were so me ti mes used o n tig h t circu its ) to be reloca ted between th e vee o f th e cy linders ra the r than behind the m as before , i n turn creating more room for bi gger reed va lve boxes an d permitting a much mo re fav orable line to the ex ha us t pipes, w h ich in turn a llowed th e o p ti m u m design to be us ed: apart from th e la st GP in Argentina, wh en a n ex perime n ta l set o f pipes was us ed, G ardner u sed the same typ e o f exhaus t design a ll yea r long. The red esig n a llowed th e en gi ne to be mad e sma ller than before, a nd a 25mm narrower five-bearing cra nkshaft to be em p loyed which red u ced th e ' o vera ll width b y th e sam e a mo u n t. H ow ever , th e wider angle betw een th e cylin ders necessita ted the us e of a . ba lance sh aft sin ce th e en gi ne no longer enjoyed th e pe rfect p rimary ba la n ce of a gO-de gree V-4 u n it, but thi s wa s tu rned to adva ntage, beca u se at the sa me time th e d irecti on of th e cra n k sh a ft was rev e r sed co m p a re d' 10 prev io us NS R500 desig n s, so th at it n o w run s forward: th e incl us ion o f a bal ance shaft m eant th e sa me gearb ox co u ld be em p loyed as before, an important cost saving. The decision to reverse th e directional rota tion of th e crank was i n response to Wayn e 'G ard n er's co m plaints abou t th e handling of the 1986 bike, wh ich he felt needed m ore weig h t o n th e front wheel. At th e sa me time, he also as ked for th e characteristics o f the engine 's power del ivery to be completely a ltered, compared to th e Fr eddie Spencerinspired 500cc H onda two-strokes o f the p a st , with th eir huge p ower outputs but lightning-switch delivery and n arrow u sable rev range high up th e sca le. For m e, th e chance to ride Wa yn e G ardner 's title-winning machine after h aving had th e good fo tune to ride both Spencer's '85 championship bike and last year's unsuccessful machine, showed to effect just h ow co m p letely Garnder has had his wi sh es granted. H onda 500cc GP devel opment is now being co nd uc ted to produce a n Au stralianstyle, rath er th an U.S.- style machine, believe m e! Because o f, ra the r th an in spi te o f, th e weather co nd itio ns a t Suzu ka for m y test , I co u ld a p p reciate the chara cter of th e NSR500D to th e ful l. The 1987 NSR500 featured w hat was effectively a comp letely new design w hich made th e engine smaller. The last thing yo u want when th e ti res are co ld a nd th e track's a bit sli ppery is a fire-breath i ng , razoredge racer wi th a n effective p o wer band of abo u t 2000 rpm , like the L uck y Stri ke Yamaha an d Ca gi va V4s I rode ea rlier in th e yea r. What yo u wa nt is someth i n g like th e N SR500D , which has th e m o s t a mazing ly fl exibl e , ye t ultrapowerfu l en g ine whose power del i very is al most like th e productionbased four-strokes G ardner spe nt so . much of his ca reer making his name on - a bike even like H onda 's R VF750 TT l giant. The NS R will pull from as low as 6000 rpm without slip p in g th e clutch, yet when reall y stron g and u sa ble power arrives a t 8000 rpm o r thereabouts, it does so without a sudden, sharp sna p, just a strong, strong r ush that" is co m pletely co ntro llable. From there up to o ver no less than 13,000 rpm th ere is a linear deliver y o f GP-winning horsepower, with maximum o u tp u t o f a ro u nd 160 bhp a t th e cran k (' o ver 150 bhp' a t th e co u nters haft) ava ilab le a t 12,000 rpm. T o ha ve such a massive power o utp u t ava ila b le, yet in co njunctio n with such a wi de HRC. w idened the included angle between the pairs of cylinders. allowing the carburetors to be moved to between the vee of the cylinders. po wer band a nd sm ooth, unsudden del ivery,' is a remarkable feat. It makes th e H onda NSR500 sta nd o u t from i ts co m peti tio n, a nd rea lly i t deserves to w in th e world ti tie o n th is basis alone. HRC ac hieved th is breakthrough of designi ng a title-w inn ing bike " which ca n be ri dden like a su pe r-roadster by jettisoning th eir ATAC vari ableexhaust volume system in favo r of a (ssh - Yam aha-like) g u illoti ne power-va lve design which varies th e height of th e exha ust p ort but is posi tione d o utside the cylin der so as (Contin u ed to page 72)

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