Sito’s bikes

Sito's Say­onara

Classic Racer - - WHAT'S INSIDE -

The quar­ter-litre class of GP rac­ing in the late 1980s was a hot­bed of devel­op­ment that sat un­der­neath some of the most ex­cep­tional rid­ers of all time – Sito be­ing one of them. Th­ese are his two most amaz­ing bikes in close de­tail.

The cur­rent Span­ish dom­i­na­tion of Mo­togp and its satel­lite classes, let alone Dorna’s own­er­ship of the se­ries as a whole, es­sen­tially dates back to ex­actly 30 years ago in 1988, when the then 28-year-old Barcelon­abased rider Al­fonso ‘Sito’ Pons won the first of his two 250cc world cham­pi­onships, aboard the fac­tory Honda NSR250 V-twin spon­sored by the coun­try’s ma­jor petroleum com­pany, Campsa. Whereas un­til then Span­ish rid­ers like An­gel Ni­eto, Ben­jamin Grau and Ri­cardo Tormo had es­sen­tially only tasted suc­cess in the 50/125cc ‘tid­dler’ classes (okay, we haven’t for­got­ten Santi Her­rero and the 250 mono­coque Ossa, but he was the ex­cep­tion rather than the rule – and you can see that bike rep­re­sented in ex­quis­ite de­tail on page 22 of this very is­sue). And with those smaller classes pri­mar­ily con­tested by diminu­tive Latins, the new wave of Span­ish rid­ers came to dom­i­nate the 250GP cat­e­gory which had much more wide­spread global ap­peal. Pons had to con­tend not only with his bel­li­cose Yamaha-mounted home-town ri­val Juan Gar­riga, both in 250GP and af­ter both of them moved up to the 500cc cat­e­gory in 1990, but also with men like Car­los Car­dus, Alex Criv­ille, Al­berto Puig and Dani Ama­train as the lead­ers of the new wave in Span­ish GP rac­ing. But while the first of Pons’ two world ti­tles in 1988 came af­ter a fe­ro­cious sea­son-long scrap with Gar­riga, who fin­ished sec­ond in the ta­ble just 10 points be­hind, 1989 saw the for­mer ar­chi­tec­tural stu­dent dom­i­nate the se­ries, wrap­ping up the cham­pi­onship ti­tle three races early af­ter win­ning seven GPS out of 15. In that sea­son Pons fin­ished ev­ery race no lower than fourth which led to a lead of 72 points over run­ner-up Rein­hold Roth on a sim­i­lar Honda. You might say he dom­i­nated the sea­son and the rea­son for such dom­i­na­tion is sim­ple: Sito not only had to con­tend with the sur­pris­ing early-sea­son com­pet­i­tive­ness of the re­vampedyz r250yamaha V-twin – re­designed for 1989 in sin­gle­crank form, like its Honda ri­val – and the awe­some tal­ent of John Kocin­ski who won two out of the year's first three GPS, but a pha­lanx of other Honda rid­ers mounted on ma­chines that out­wardly at least, were iden­ti­cal to his own. As the sea­son pro­gressed, and Honda in­ten­si­fied devel­op­ment af­ter be­ing beaten by the new Yama­has in three out of the first four races, the chal­lenge to the Span­ish reign­ing cham­pion came ex­clu­sively from his fel­low Honda rid­ers: the sight of a sex­tet of Hon­das bat­tling for vic­tory be­came com­mon­place. One rea­son for Pons’ reign was ob­vi­ously Sito’s be­lief in him­self af­ter win­ning the ti­tle for the first time in 1988. Re­tain­ing a cham­pi­onship can some­times be even harder than win­ning it for the first time, but in this case the No.1 plate gave Pons an ex­tra aura of in­vin­ci­bil­ity, which his finely-honed race­craft ex­ploited to the full. The sight of cham­pi­onship run­ner-up

Rein­hold Roth in tears on the Ri­jeka ros­trum summed it all up, af­ter be­ing out­foxed yet again by the Span­ish ace in the last lap run to the flag: “Won't you at least let me win one race?” he asked. HRC cer­tainly helped fuel this supremacy by giv­ing Sito max­i­mum sup­port through­out the sea­son, es­pe­cially af­ter Yamaha threat­ened to win back the 250GP ti­tle af­ter the first four races. There’s lit­tle doubt that Ja­panese rider Masahiro Shimizu per­formed a lit­tle-known but vi­tal devel­op­ment role in this re­spect, test­ing new com­po­nents and en­gine set­tings in early qual­i­fy­ing that were in­cor­po­rated in Sito’s bike for fi­nal prac­tice and the race if they worked, even to the point of the Ja­panese rider’s en­gine be­ing fit­ted in Sito’s bike for race day, if con­sid­ered de­sir­able. Fi­nally, as in 1988, the in­flu­ence of An­to­nio Cobas can’t be over­es­ti­mated. The Span­ish de­signer found time from his own team’s suc­cess­ful as­sault on the world 125 ti­tle (in which his rider Alex Criv­ille iron­i­cally de­feated both works Hon­das to win the cham­pi­onship!)

to work his tech­ni­cal wiz­ardry on the chas­sis of Sito’s bike. With the best en­gine, the best chas­sis set-up and the best rider, is it any won­der that the Campsa Honda team re­tained its world ti­tle in 1989?

The why

In at­tempt­ing to du­pli­cate Spencer’s hard­fought 1985 world cham­pi­onship vic­tory on the unique NSR250, Honda got badly blind­sided in 1986 by the to­tal dom­i­nance of Car­los Lavado on theyama­hayzr250, who won six GP races en route to the ti­tle. As HRC di­rec­tor and Honda GP boss Yoichi Oguma told me when I tested Shimizu’s bike at Suzuka, Honda had made the mis­take of com­pletely re­design­ing the in­ter­nals of the en­gine com­pared to Fred­die Spencer’s unique ti­tle-win­ner from the year be­fore. “We should have had con­fi­dence in our ex­ist­ing devel­op­ment skills, not done so much work on re­design­ing a proven win­ner,” he said. So for 1987 the third-gen­er­a­tion ma­chine con­tained no ma­jor de­sign changes, only a host of small im­prove­ments and tweaks which to­gether re­sulted in a For­mula Honda steam­roller – Honda rid­ers tak­ing the first five places in a world cham­pi­onship ta­ble topped by wily West Ger­man vet­eran Toni Mang. It looked like it was go­ing to be Pons’ year at the start of 1987, un­til a fall in prac­tice at his home race in Jerez gave him a painful hand in­jury which ham­pered him for a good part of the sea­son. De­spite that, Sito scored points in ev­ery GP ex­cept Swe­den, where what the Ja­panese termed ‘ig­ni­tion trou­ble’ (fac­tory Hon­das never of­fi­cially seized!) caused his only me­chan­i­cal re­tire­ment that year.

The tech­ni­cal

Un­like its 1987 NSR500 V4 sis­ter bike, on which the vee an­gle be­tween the cylin­ders was opened out to 112º in or­der to in­crease reed valve area, lo­cate the carbs be­tween the cylin­ders and ob­tain an im­proved ex­haust line – that year’s NSR250 kept the Spencer bike’s 90° V-twin con­fig­u­ra­tion. That meant it didn’t need a bal­ance shaft to elim­i­nate vi­bra­tion, which Honda boss Oguma said would have sapped vi­tal power, as well as mak­ing the en­gine un­nec­es­sar­ily heav­ier and more bulky. But the change to two sep­a­rate round­bod­ied 38mm Kei­hin alu­minium carbs was purely on the grounds of cost. With the bike al­ready on the 90kg class weight limit, Honda didn't need to go to the ex­pense of em­ploy­ing the ex­pen­sive mag­ne­sium twin-choke sin­gle-body Kei­hins used on the NSR500 and in­deed on Spencer's NSR250 ti­tle-win­ner two years ear­lier. Honda’s main devel­op­ment over the win­ter went into that tra­di­tion­ally fer­tile area of de­sign for the two-stroke en­gi­neer, the cylin­ders. In­stead of the Atac-equipped 1986 en­gine with its vari­able-vol­ume ex­haust sys­tem, Honda en­gi­neers adopted a Yamaha-like vari­able ex­haust port power-valve sys­tem, ac­tu­ated by an elec­tric mo­tor con­trolled elec­tron­i­cally off the tacho. At the same time, they re­worked the five trans­fer/sin­gle ex­haust port cylin­ders and re­vised the ex­haust sys­tem which, on a twin-cylin­der 250, doesn’t take up so much room as on a four-cylin­der 500, which in turn means that pipe de­sign isn’t com­pro­mised by space lim­i­ta­tions. Still, the rear-mounted carbs did mean that the left-hand pipe curved round from the for­ward-fac­ing ex­haust port, prob­a­bly of­fer­ing a less ideal shape than its part­ner, which

ex­ited straight from the bot­tom rear side of the right port. Pre­sum­ably, the in­crease in vi­bra­tion which would have been no­tice­able on a sin­gle­crank V-twin had they in­creased the cylin­ders’ in­cluded an­gle from 90° to the 112° of the 500, mit­i­gated against putting the carbs in a for­ward-fac­ing po­si­tion in a wider space be­tween the cylin­ders as on the 500 – which would have of­fered a su­pe­rior ex­haust run, as Yamaha later dis­cov­ered with their V-twin TZ250. On a V4, the slight in­crease in pri­mary im­bal­ance would be less no­tice­able. The re­sult of HRC’S mod­i­fi­ca­tions to the 54 x 54.5mm en­gine was to raise de­clared out­put to 80bhp at 12,800rpm, but more im­por­tantly to also im­prove bot­tom end torque and midrange per­for­mance. On a tight track like Calafat where I rode Sito’s 1987 bike post-sea­son this was es­pe­cially no­tice­able. The Honda seemed to leap out of sec­ond-gear cor­ners with no­tice­ably added zest com­pared to the Ro­tax-pow­ered Aprilia of Loris Reg­giani that I'd been rid­ing an hour ear­lier. The fact that the slightly big­ger Honda fit­ted me bet­ter than the low-slung Ital­ian bike was a bonus, but I felt bet­ter able to power out of turns on the Aprilia be­cause it han­dled more nim­bly, yet it was the Honda which I ac­tu­ally went quicker on, be­cause of its su­pe­rior torque. This was a highly ride­able bike that on many cir­cuits would have been far eas­ier to ride, and even ca­pa­ble of lap­ping faster, than its V4 500cc cousin. I'm not ashamed in ad­mit­ting that on Shimizu’s NSR250 I’d lapped Suzuka faster on a cold, slightly damp day than I did on Wayne Gar­dener’s ti­tlewin­ning NSR500! Yet ac­cord­ing to Oguma this was all pre­dictable: “The tar­get for our NSR250 GP project team is to beat the 500cc lap record at both Tsukuba and Sugo cir­cuits,” he said. “Al­ready they are very close, and with the sort of per­for­mance we are now achiev­ing with our NSR250, to­gether with its light weight and easy han­dling, I think it will not be long be­fore they do this.” [They did! – Ed]. Max­i­mum power on the 1987 NSR250 was de­liv­ered at 12,100rpm, but it pulled hard from around 8,500 revs, giv­ing an ac­cept­ably wide us­able spread of power, though there was zero over­rev – power tailed off abruptly af­ter 12,400rpm or so. But it felt so strong for a 250 – more like a 350 in the old days com­pared to a 500 – and the cas­sette-type gear­box en­abled swift ra­tio changes. How­ever, even at my re­duced speed com­pared to Sito I could dis­cover the trac­tion prob­lems with the bike thanks to its ul­tra-short 1310mm wheel­base and far for­ward 56/44% weight dis­tri­bu­tion, which Oguma’s en­gi­neers had opted for in an at­tempt to make the Honda turn as nim­bly as the more ag­ile, but slower, Yama­has. Ex­it­ing the two tight turns at the north­ern end of the Calafat track the rear Miche­lin ra­dial would spin up re­peat­edly, even with my heav­ier weight on board. I also found that the bike be­came un­set­tled if you braked very hard, the back wheel streetsweep­ing around in the air. This was surely a fac­tor of the ex­treme for­ward weight bias of Honda’s new chas­sis for the NSR250 that sea­son, cleaner and neater but also more sturdy than pre­vi­ous de­signs, weigh­ing close to the 90kg class weight limit, how­ever. But this front­wards ac­cen­tu­a­tion of that weight, cou­pled with the ex­cel­lent brak­ing per­for­mance of the twin 270mm Nissin discs and their four-piston calipers, was cer­tainly re­spon­si­ble for the in­sta­bil­ity un­der brak­ing that had made Honda rid­ers like Sito sus­cep­ti­ble to rushes up the in­side on the part of hard brak­ers like Loris Reg­giani and the Yamaha-mounted Luca Cadalora. I also wasn’t happy with the way the Honda washed out the front wheel as you turn into cer­tain bends in sec­ond or third gear. Sur­pris­ingly,

the steer­ing head an­gle of the 43mm Showa tele­scopic fork was fixed at 23°, and trail could only be al­tered by rais­ing or low­er­ing the ride height at the rear – there were no al­ter­na­tive tripleclamps! To re­solve th­ese han­dling prob­lems for 1988 Sito went back to the fu­ture and en­listed the aid of his near neigh­bour and for­mer chas­sis en­gi­neer An­to­nio Cobas, to work along­side his crew chief Santi Mulero in re­fin­ing the setup of the NSR250 frame. The 1988 NSR250 with which Sito won the first of his two world ti­tles was ef­fec­tively an en­tirely new bike, al­beit still di­rectly de­rived from Fred­die Spencer's 1985 world cham­pion. Mang’s 1987 ti­tle-win­ner had scaled right on the FIM’S 90kg min­i­mum weight limit for the 250 class, leav­ing Honda with the right kind of prob­lem – where to add weight, rather than re­duce it. Oguma con­firmed this: “We could eas­ily re­duce to­tal weight to 85kg with no prob­lem, and not too much ex­pense. “We there­fore have paid close at­ten­tion to im­prov­ing the han­dling and re­duc­ing frontal area. For this rea­son, in re­design­ing the NSR250 en­gine for 1988, we nar­rowed it only by 3mm, but also short­ened it by mak­ing the pri­mary gear smaller and ro­tat­ing the gear­box shafts slightly so as to bring the whole gear clus­ter closer to the crank. The ad­van­tage of this is to re­duce the po­lar mo­ment for im­proved han­dling. We also have a lit­tle more power than be­fore!” Since the 1987 NSR250 was of­fi­cially de­clared to yield 80bhp at 12,800rpm, we may safely take it that the 1988 ti­tle-win­ner churned out about 82bhp, prob­a­bly peak­ing at 12,500rpm or so. Oguma-san wouldn’t con­firm that this time, though! Honda achieved this with the aid of new cylin­ders and pipes (though they sur­pris­ingly used the same de­sign for all tracks and con­di­tions), still in­cor­po­rat­ing the elec­tronic power valve in­tro­duced for 1987 to re­place the ATAC sys­tem used hith­erto. And HRC still hadn’t opened up the in­cluded cylin­der an­gle to 112º as on its NSR500 V4, though Yamaha did do this for 1988 on both its 250 and 500 twin-crank YZR de­signs, to of­fer a greater reed valve area, and im­prove car­bu­ra­tion. If the en­gine was broadly as be­fore, the 1988 NSR250’S chas­sis re­ceived a lot of at­ten­tion over the win­ter. The ex­truded twin-spar al­loy frame was not only ti­died up but be­came stiffer and a lit­tle more com­pact, while the wheel­base was length­ened slightly to 1330mm to re­dress the 1987 NSR250’S lack of trac­tion ex­it­ing turns. At the same time, the beefy 43mm Showa front forks lost their TRAC brake­op­er­ated an­tidive setup, in favour of a plain sin­gle-rate spring cou­pled with a pro-squat rear end link­age and some so­phis­ti­cated front end damp­ing. Shimizu’s bike ap­peared at Jerez with car­bon fi­bre fork slid­ers but th­ese were works spe­cials which the lease NSRS weren’t sup­plied with – and that in­cluded Sito’s Campsa team. But a ma­jor dif­fer­ence for all NSRS that sea­son was the fit­ting of a curved ra­di­a­tor, which en­abled the ob­jec­tive of re­duced frontal area to be met, even with the sin­gle-crank en­gine which was in­her­ently wider than the twin-crank V-twin. As well, the more com­pacted en­gine mass was moved closer to the front wheel. Cobas’ mod­i­fi­ca­tions to the 1988 NSR250 con­sisted of a com­pletely new rear sus­pen­sion link to of­fer an im­proved curve to the ris­ing rate, al­ter­ations to the Showa rear shock it­self, an al­tered shape to the fuel tank to re­vise weight dis­tri­bu­tion with Sito in place, a re­vised seat with the un­der­side faired-in com­pletely to of­fer less of a pocket for slower bikes (i.e. Gar­riga's Yamaha!) to slip­stream the faster Honda in down the straight, and much else in­clud­ing gen­eral setup at the track. Sito said: “Some rid­ers just like to just get on the bike and ride it. “But I pre­fer to spend as much time as pos­si­ble at each cir­cuit ex­per­i­ment­ing, so as to get the best pos­si­ble setup. Hav­ing An­to­nio with us that year halved the time it took to achieve that, sim­ply be­cause he could pre­dict the likely ef­fect of each small change we made so ac­cu­rately that we could de­cide in ad­vance whether it was worth do­ing or not. “One of the prob­lems with last year’s bike was that it wouldn’t steer fast enough for me into turns,” ex­plained Sito at the time. “An­to­nio al­tered the steer­ing ge­om­e­try and weight dis­tri­bu­tion by rais­ing the rear end and mak­ing other changes to the front, as well as re­design­ing the fuel tank, so that now we have more weight on the front wheel, a steeper ef­fec­tive head an­gle, and a much quicker steer­ing bike than the one Honda sent us. It was a cru­cial fac­tor in our suc­cess this sea­son.” The fact that he had the most horse­power in the class while rev­el­ling in such a ride­able bike was one rea­son Sito’s Honda was so hard to beat that year – but it also puts into per­spec­tive Juan Gar­riga’s re­mark­able per­for­mances on the slower, but nim­bler Yamaha. “The Honda and the Yamaha ac­cel­er­ate much the same,” said Sito: “but my bike is def­i­nitely faster in midrange and top speed. How­ever, Reg­giani’s Aprilia is even faster still on ab­so­lute top speed, just that it doesn't have such a good power de­liv­ery, and cer­tainly doesn’t han­dle so good. But even with the mod­i­fi­ca­tions we made to my Honda this year, the Yamaha still han­dles bet­ter, es­pe­cially on the way into a turn.” The Cobas mod­i­fi­ca­tions to Sito’s Honda en­sured that it steered al­most as fast as a JJCobas, but with more fi­nesse, and a lot more con­trol­lably. You could round cor­ners prac­ti­cally on au­topi­lot, and the few re­main­ing bumps of the freshly resur­faced Calafat cir­cuit were easy meat for the smooth-ac­tion rear sus­pen­sion. But for 1989 in pro­vid­ing Sito with a bike to de­fend his ti­tle with, Honda de­liv­ered that track tester’s night­mare: the per­fect race bike! The 1988 ver­sion at least had the soggy and in­ad­e­quate brakes for me to crit­i­cise, but since then Nissin had ob­vi­ously done their home­work, and the re­sult was a front brake setup that could be ca­ressed with a fin­ger if you just wanted to scrub off a bit of speed go­ing into the chi­cane be­hind the pits at Calafat, yet gave im­pres­sive, in­stant brak­ing for the hair­pin at the end of the main straight. Sen­si­tiv­ity, cou­pled with stop­ping power – in spite of the smaller 275mm front discs that Sito used (his fel­low Honda rid­ers fit­ted big­ger 290mm discs, which in­creased un­sprung weight and had an in­creased gy­ro­scopic ef­fect on the steer­ing).

Words: Alan Cath­cart Pho­tos: Emilio Jimenez and Don Mor­ley

Do you think that the ‘Champ’ brand­ing was sub­tle enough in 1989?

A long swingarm helped sta­bil­ity on the fastest parts of the track. Over 80bhp from 249cc was made most po­tent by the trim 92kg weight.

From the front you can see just how nar­row the NSR was.

Fac­tory two-stroke ex­hausts are pure dark-arts magic.

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