Cycle News - Archive Issues - 1990's

pits, the Castrol bike needed a lot of muscle to make it stay on line - it kept wanting to head fo r the ou tside of the track under hard acceleration. Considering that the geometry on this works bike could hardly be less stock, thi s wa s a bit of a s u rp rise - H RC h a ve gone fu ll cir cle, without resolving the probl em . And though the bike wa s stable around fast turns, even if you had to keep giving it a good tug on the bars to make it stee r where you wanted, it didn't like hitting a bump under power, like on the fast, fifthgear right-hander before the Spoon Curve. There's a dip in the surface there, which the Michael Doohan NSRSOO I'd been riding earlier had just shrugged off at even higher speeds than on the Superbike. Here, every lap, the RC45 pul~d a vicious tank-slapper on me, flapping the bars in my hands as !fought to convince myself it was okay to keep th e throttle w ide open. Sorry - I h ave to admit I di dn't succeed : I'm sure Slight-san is a braver man than 1 am, but considering the Showa forks on the works RC45 are the same as o n the NSRSOO, just set up a little stiffer for the extra wei ght of the Superbike, I d on't think this is how it ou ght to behave. Honda apparently didn't think so either, because the Castrol team received a successio n of frames throughout th e season, each one altered within the limitations imposed by th e Superb ike rules. This mainly entailed successively greater braci ng of the stru cture, w ith welded-on strengthening plates all around the inside of the frame spars, as we ll as arou nd the steering head and swing arm pivot, and o f course - the swi nga r m it se lf. Th is didn't help the H onda's we ight hand icap , though w hat was initially a rather po rky bike was slimmed down by season's end to 360 p ou nd s h a lf-d ry (i. e . with oil/ w ater, no fuel), still 8.8 po unds over the new four -cylinde r wei ght limit, but it al so didn't seem to he lp th e h andlin g much either. Th e team wanted t o alter the sw ing arm pivo t in an effort to cure the understeer, but the rather su rp rising fixed position on the stock RC45 - the ZXR has an adjustab le pivot, for example - wa sn't altered all season, though HRC did produce three different links for the re ar shock. The y also experimented a lot with front-end geometry : Superbike rul es d on't allow you to cut 'n' shut the fram e to alter the head ang le or change the posi tion of the steering head, but you can of course raise or lower the rear rid e he ight to effectively change th e fork angle, as well as play around with offsets to alter the trail. Honda did all that - Slight ran his bike abo u t 5mm lower at th e rear end than Polen did, for more neu tr al handling at the expense of more understeer, w hich is perhaps wh y this was so noticeable w ith the bike at Suzuka, fitted with the lon ger sw ingarm - but they also pulled the stee ring column back 3m m, by means of boring ou t the head stem and fitting eccentric cups. This inevi tably increased the fron tend bias of a bik e that alrea dy had a lot of weigh t on th e front wheel - th e Rumi's stock geom etry yielded a 53 /47% spli t in an attem pt to make it tum more quickly, while a 4mm shim inserted under or above the head bearing also effectively allowed Honda to alter the effective location of the crankshaft center.over an 8mm range. • Sligh t runs it in th e lo w e r se tting, which wo uld account for the bike feeling so stable around fas t turns, but would also explain why it feels hard to change direction in slower ones. Obviously this all affe cts the basic head-angle setting, too, tho ugh at 22.5 degrees Slight ran it . about 0.5 ~egrees less steep than Polen d id, because of his lower rear ride height - Polen had the rear end jacked up to try to make the bike tum quicker. Bu t o ne effect of pulling back the stee ring he ad w as that when the Castrol team fin ally d id get the alternative fork offset s from Showa th ey'd been aski ng for all yea r th e y h ad to make do with the s to ck 32.5mm ones for two- thi rds of the season, until they finally got a 30mm o ne a t Mugello that would have increased trail and perh aps if fitted would have made the bike ride the bumps better at Suzuka they couldn't fit the 27mm offsets they really w anted to try, because th e front wheel wouldn't have cleared the radiator. I think from ridi ng the bike at Suzuka and looking at all these changes mad e to the cha ssis se tu p, one conclusion seems unavoidable .- the engine is in the wrong place in the ch assis. H onda m ust have realized th is too, or else th ey wou ld n ' t have gone to such lengths to try to crea te the same effect as what they aren't un der Superbike rules ab le to do, w hich is to build a new frame with the engine in a different place . It feels to me as if the motor is too far fo rward, a problem exacerbated by the long sw inga rm fitted to the bike I rode eve n with a pulled-back steering head. Th e ease w ith which yo u can ha ve the back wheel w avin g in the air under the super braking po wer of the Brembo carbo n d iscs - w hich ar e due to be banned next year - confirms this . Thou gh the Castrol RC45 is g reat on turn-in, with the front Dunlop glued to the ground on the brak es and extra stop ping power available from engine brak ing via the sprag clut ch wi thou t risking locking up the rear w heel, you also have to be prepared to try to turn in to th e apex with th e back wheel some way off the ground, waving in the breeze - definitely an acq uired skill! Add to this the fact th at the team can' t use as mu ch trail as they'd like because of the clearance problem w ith the rad iat or, and yo u ha ve the recipe for the instability ove r bumps - intensified by th e stee p effective head angle - that I ex perienced . Considering the ROO, and especially the RVF750 F-1 bike from which the RC45 was allegedly derived , handled so well, it's a bit of a surprise to find that Honda still hasn't Sorte d out its new Superbike's track manners . But if there's a fundamental problem like the engine locati on being wrong, perhaps that might explain it. The engine's an other matter, and here I'm sure it's only a matter of time before HRC's engineers tap the 16-valve V-four for the extra power it needs to deliver in midrange. On e thing that w as noti ceable is that the engine in the Slight bike I rod e had noticeabl y qui cker pickup in engine speed than the Rumi bike, an d felt as if it had a ligh ter crank than standa rd . Th e way the revs died away so fast under braking for slower turns seems to confirm this - yet for mos t of th e season the Castr ol team actually fitted a 24-hourrace ignitio n wit h a he avier flyw heel to ad d a couple of po un ds to the cra nk on faster tra cks like Zeltweg and Asse n (as well as for any we t race), w ith the object of keeping the revs up by cutting d own the loss in rpm on each gear change from around 1200 rpm to about 800 rpm. That tells you th at th is was still a top-end motorcycle, in spite of the extra midrange an d improved power delivery. But with the sweet-action HRC speed-shifter fitted, yo u d on 't see m to lose any significan t revs with the setup I had at Suzuka. It's also interesting to note that Honda themselves do n' t use a high compression ratio with the bike, designed as it is to run on low-lead fuel because the crank wei ght is wrong and a high compression kills the top-end speed. Bu t 1994 is over and done with, and (Above) Naked gun. Does the RC45 feature a design flaw that has the engine sitllng too far forward in the chassis? (Right) In a search to make the bike handle better. HRC has experimented with different geometries. using different offsets. (Below) The factory Honda used 43mm Showa forks in 1994. Honda now has eyes set on success with the RC45 in 1995. I have to say it's a big p it y they co u ld n ' t find some way of incorporating Anthony Gobert into their works set u p, because he showed not only in winning the Oz title, but also in beating Aaron Slight in the seco nd race in Japan that h e had th e m easure of th e bi ke so meth ing Dou g Polen frankl y d idn' t see m to ha ve apart from a brief midseason burst. But now Gobert's gone Green, leaving Aaron an d Dou g to put Honda back on top of the Superbike pile where th ey were half a d ecade ago w it h th e RO O. With an intensive winter test season that will see the Castrol team practically living at Phillip Island, I'm sure Ho nda w ill start unlocking some more of the RC45' s hidden eng ine performance. But will they be able to make the chassis w o rk properly ? Better ask Rumi how th ey m ade th eir Ohlins-equipped bike with only a little less po wer but a much less friend ly po w er deli very handle so well. Michelin tires ? l~ Castrol Honda RC4S S~eciftcations Engine Dimensions Capacity Output Fuel system Ignition Gearbox Clutch Chassis Suspension Front Rear Head angle Trail : WMelbase Weight Weight distribution Ur Brakes Front Rear WhMIsItlres Front Rear Top speed 0wMr Water·cooled dohc 16-valve 90-degree V-Iour tour-stroke with gea r camshaft drive and four valves per cylinder 72 x 46mm • 12.2:1· 143 bhp at 14,000 rpm (at rear wheel) Honda·PGM FI electronic fuel injecti n with 4 x 46mm throttlebodies o Nippondenso digital electronic COl s -spe ed with HRC spee d-stutter and gear primary drive 9-plate oil-bath spraq -type Extruded aluminum twin- spar frame with cast stee ring hea d and swingarm pivot 43mm Showa inverted telescopic forks Gast aluminum Pro-Arm single-sided swingarm with ProUnk rising·rate linkage and single Showa shock 22.5 degrees Notavailable 1430mm (as tested ) 360.6 pounds with oil/water, no fuel 54146% 2 x 290mm Bramba carbon discs withfour-piston Brembo calipers 22Omm Honda steel disc with two-piston Nissincaliper Dunlopradial on 3.75-ln. Honda wheel Dunlopradial on 6.25-in. Honda wheel 181.04 mph (Hockenheim) Honda Racing Corporation. Saitama. Japan 130170-17 190155-17 33

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