Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/128245
RC V's overall a rc hi te ct u re tha t is th e k ey fact or , with the V5 engi ne very much a fully stresse d p art of th e cha ssis package, and t he mass of the bike c om pacte d around it. This includes th e 6.25 -gallon fu el load , wh ich i s p osit ion ed low d own i n th e ce nte r of th e wh eelba se, 3 0 p er c ent o f it und er th e seat , t h e rest in th e rear s ec tion of t he air box shrou d . ( It see ms H on d a has succeeded in p er su ad ing the FIM to pos tpone the intro du ct ion of the 5.72 -g al Ion ru le unti l 2005, much to t he an n o ya n c e of A p r i li a , espec iall y, with its more fru gal trip le , presumabl y o n the grounds that fuel ec onomy is p o t en ti a ll y a real p rob le m fo r t he fi ve -c y lind er revs th an an yt h i n g e lse on the Mo t o GP gr i d, Ho nda h a s so f ar re sis ted t his op tion in order to reduce maintenance costs - an exa mple, accord ing to Kanaumi, i s that there are three rings employed on each piston , not tw o, as is more no rm al on a h igh -performance fourstroke engine. So under present co n ditions, t he c o m p a c t and light y et still robust RCV eng ine design goes a remarkable 2480 miles between major overhauls , when the crank shaft an d cases are replaced . T hat's one -th ird greater m ileage than last yea r, with va lves, p istons and c o n rods renewed at 124 0 -m il e intervals , an d the h eads re mo ved every 620 m il es (l .e., in bet ween rac es ) , so the titaniu m valv es ca n be chec k ed and the top end freshen ed u p wi th new p i ston ri ngs . Ju st like a very fast Superbike... The multiplate ramp-type dry sli p per clutch is lo cated on the right side of the eng in e behind a plate that unbolts to give access to the cassette-type six -speed ge arbox , wh ich i s read ily extra ctabl e to perform quick internal ratio changes in just 20 m inutes without even removing the fa iring. Th is , however , proved to b e the Hond a ' s onl y r eal A ch ill es ' heel in its 2002 de b ut sea son, wh en an o v e r h e a ti n g cl u t c h c au sed a n erra tic response on downshifts, le ading to problems under braking. How ever , Honda r ejected the idea o f cop y ing Yamaha' s e l ec t r o nic a lly co ntro ll ed " bac k t orqu e co n ve rte r," which esse ntially rem o ves all eng ine brak ing , and work ed instea d on refin i n g t he ope ra tio n o f its exis t i ng cl utch by a lte ri n g the ch a rac te r o f th e eng ine t o suit a va r iab le set of ci rc ums t ances. This i s ac hie ved v ia a so-c a lle d " dec eleratio n co ntrol" sy ste m , wh ereby the e n g i ne- m a na ge me n t E CU m onitors e ng ine speed, rea r-wh eel speed , gear sel e ct ed a n d throttl e position , all to judge when is the right m oment to activat e tw o o r m ore soleno id valves , whi ch o pe n a p ipe join in g the airbox to the in let ports . With a closed throttle , th e unpressurized system allows ex tra ai r into the in let ports of all fou r cyl inders, red ucing the vacuum under the throttle butter flies (there are tw o per cylinder for the same p urpose as on many street bik es : to enhance bottom- end d rive and smooth out the pickup) . This has the effec t of increasing th e idl e sp eed and thus reducing en g in e brak ing , enough to prevent rear -wheel cha tt er and so en ha nc e stability , as well as improving rider c onfi denc e - and can of course be varied according to rider choi ce by simply altering the map ping of the relevant ECU prog ram. It's th e Honda Way - even if a similar sys tem was developed over a decade ago by Bosch and was fitted to BMW a n d M e r c ed e s -B en z high-perfo r mance ca rs... Honda's ex isti ng three-way opti on of engine-manage ment maps is deliv ere d to it s rid ers via the switch on the left -h and cli pon (sad ly a bsent fro m th e test bike) , which giv es th em on e map f o r a c lut c h start off th e lin e , another for the early part of the rac e, and the n allows them to swap to a softer sett i n g as t ires d et e r iorate and/or th e track be comes sl ippery . Add th at to the adoption by Honda of el e ct roni c t r a ctio n contr ol , which mon itors an d compares fron t - an d rear- wheel sp eed in order to tame the pow er del ivery in the lowe r gea rs by means o f ret arding or even cutting t he ign ition momentarily o nce th e rear tire starts to slide, and it's clea r that the elec tro nic ingredi ent in mak ing a rac e-winn ing Mot oGP co nte nde r is eve r m ore cr ucial. A s before , the RC211 V engi ne is in stalled in an outw ard ly co nventio n a l- lookin g , ope n-cradle , alu mi num twin -spar c h a ss is , fro m whi c h th e eng ine ca n b e d ro p pe d in ju st 2 0 minut es . How ever , in o rde r t o a id con t rolla b ility, it d o es v ary sli g ht ly from th e '02 version by having a ce rt ain degree of so -call ed " c ont r o ll ed fl ex " o bt ained from being made from sev era l sm all all oy pressings weld ed togeth er , so that - in th eory , at least a differen t frame with a different amount of flex d ial ed in can be m ade quite eas ily for each rider. Yet it's the Brno, loc ated und er the upper tr iple cl am p . Th e rear-suspen sion desig n is the same as in 200 2 and featur es a single fu lly adju st ab le Sh ow a sh ock anchored at both end s to the heavily bra ced fa br icated swingarm , rathe r than the top e n d mounted to the c h as si s , as o n more con ventional monos ho ck design s. This was o rig inall y adopt ed in order to f ree u p space for th e under -seat fuel tank , in turn allow ing th e desired concentra t io n of ma ss - but Honda engi neer s be li ev e th e syste m has th e spin off b e n ef it of re du c i n g c hatt er b y no longer transferrin g such forces to the ch assis, since the shock is no lo nger attached t o it, but ins te a d largel y c o nt a i n i ng th o se forces w i t h in th e sw inga rm , where th e sho ck se tt ings and tire are better eq uip pe d t o dial them out. An adj usta b le swi n ga rm pivot is still not incl uded in th e RCV chassis, enq ine.) T h i s not onl y reduces th e polar moment by lowering the ce nte r of mass and locating it closer t o th e c . of g. than on a more conventional b ike for more consistent and pre dictable handling via reduced weight transfer under braking , acceleration and turn ing, it also means t h at the b ik e 's behavior doesn 't chan ge as much during the course of a rac e as the fuel load lightens. Th is also means that the RC2 1 1V's w i r ing h arn ess i s v ery short , and indeed the whole bi k e looks much less messy and cl uttered wi th w ir ing t ha n , sa y , the Yamaha o r Aprilia. Honda says the RCV cha ssis deli vers 85 percent of fu ll h and ling p erf or mance fro m the start o f a rac e, with a fu ll fu el t an k. Moreover , it evidently has a ve ry tire-friendly firing o rder fo r th e cy li n de r s, with a sem ibig- ba ng co nfi gu rati o n, which m eant RCV rid ers ar e cons istently a b le t o ch oo se so ft er re ar ti re s t h a n their Mot oGP op positio n. A factor in this is the RC2 11 V's Unit Pro -Link rear -su spension design, matched up fro n t by the rel at i ve l y conventiona l 45mm Showa u p sid e down f o rk s, which th is yea r fea ture a n elec t ronically co ntrolled rota ry stee ri ng damper that fir st appeared at but Kanaumi admits that th e pos ition was changed fro m the 2002 machine to improve tr action; presumably this is the frame t hat was first tested by Rossi in Sepang last winter, which for sure had an altered sw ingarm pivot. The steering -head angle is similarly f ixed , he states - all the rider can play with is the trail ( via exchangeable offsets fo r the 1.8 -inch Showa upsid e down f o r k s), a nd r id e he ight. At a cl a imed 325 .6 p ou nd s with o il/fu el but no water, th e Honda RC2 1 I V is just 6.6 pou nds over the five-cyli nde r we ight limit, but Ka na umi says they can live with this "because feeli ng of bike is m ore im po rta nt." Ok ay, now wh at? How do es Honda inte n d t o resp on d t o th e inc rea sed threat from Yamaha in 2004 , let alone stay ahea d of the Italian stallions? " W e w i ll c o n ti n u e w ith this m a chin e, b u t of co u r s e w e have m an y id eas how to improve it for next se ason , " say s K anaum i. " W e m ade th is conc ept th ree year s ago - but we did not yet ach iev e maximum perfo r m ance from it yet. Next year, I want to see this!" As in, watch out, Valentino - we have lots m ore perfo rm ance loc k ed up in here! Let' s see, now - 240 plus lOpercent equals ... well , yo u do the ma th! CIIII cycle n e _ S • JANUARY 7 , 2004 59