Sito’s bikes
Sito's Sayonara
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).