THE RISE OF THE RGV500
One man’s vision and another’s hard graft turned Suzuki’s 500 GP bike from pretty also-ran into the title-winning best in class
How Suzuki’s twin-crank 500cc V4 went from slow and fickle to world domination
Anew chapter in Suzuki’s racing history began on August 23, 1986. The prototype RGV500 XR71 was unveiled during the San Marino GP, following months of speculation about Suzuki’s plans. This was a serious statement of intent – not only was the factory confirming its commitment to Grand Prix racing, it had also built a bike unlike any Suzuki before.
Their square-four, rotary-valve RG500 two-stroke had been at the front of GPS since the mid-1970s, both for the factory and privateers. However, Suzuki hadn’t won the premier-class title since 1982 with Franco Uncini, and stopped making customer-spec machines in 1983. Factory-backed teams slogged on until ’86, but the RG was outpaced and Suzuki management wanted to pull out; 500s had become a costly high-tech power struggle, so they wanted to focus efforts on street-based four-stroke racers, which had added importance given the launch of the GSX-R750 in 1985. There was a valiant rearguard action from within the factory team, however.
Led by road racing manager (and former GP winner) Mitsuo Itoh, a two-stroke faction resisted corporate pressure. The unexpected success of the road-going RG500 race replica allowed Itoh to make the point that a two-stroke GP programme could have commercial as well as promotional benefits, so the pretence was maintained that a new two-stroke racer could be a prototype for a future Suzuki roadster. Following Yamaha’s lead, Itoh’s all-new RGV500 XR71 used a twin-crank V4 layout – effectively two parallel twins, one behind the other, with cranks geared together and the banks of cylinders set at an 80˚ angle. Unlike the Yam, its cranks rotated in the same forward direction, necessitating the use of an intermediate shaft. It measured 56 x 50.7mm (dimensions used throughout the RGV line) and was the first Suzuki with reed-valve induction. Flat-slide Mikuni magnesium carbs were like the Yamaha’s, but with larger chokes and a different slide mechanism. Suzuki’s proven electronically-operated Power Chamber system gave variable exhaust dimensions, with an output of over 140bhp at 11,500rpm. Engine weight was given as 50kg, so a
best-guess overall weight was 130kg – not bad, but the limit was 120kg, and Suzuki’s first proper attempt at a modern twin-spar frame looked large and heavy. Forks and shock were by Kayaba.
Itoh said they wanted more power than the old RG but also a smoother delivery, and test riders reported lots of midrange and a smooth transition into the power. However, they also said the engine was reluctant to rev, with ground clearance limited by bulky lower exhausts.
With new cylinders and crankcases created over winter, Suzuki’s RGV500 made its race debut as the XR72 at a wet Japanese GP at Suzuka in March 1987. Test rider Takumi Ito made fine use of the easy power delivery to finish third. When Kevin Schwantz, fitting in a few GPS while trying to win the US Superbike title, finished fourth at the next race in Spain, it seemed Suzuki had hit the ground running. But the twisty Jerez track favoured the RGV’S midrange and disguised its lack of top-end speed – full-time rider Kenny Irons struggled to be competitive for the rest of the season, and suffered many mechanical gremlins.
Suzuki went big time in 1988, securing backing from Pepsi cola and signing Schwantz for his first GP season. Their new XR74 version of the RGV had modified cylinders, new exhausts (with both lower pipes exiting on the right), and a bewildering choice of ratios for the extractable six-speed gearbox. The frame was altered, Showa suspension replaced Kayaba, and weight came down. Suzuki claimed over 150bhp at 12,300rpm, yet the engine was as rideable as ever – Schwantz won the first race of the season at Suzuka, and won again at a damp Nürburgring. He made the rostrum at other races, yet only finished eighth in the championship; despite a continuous flow of parts all season, his Suzuki was still handicapped by its top end. More speed needed...
The solution was a complete redesign for 1989. The XR75 had counter-rotating cranks, cancelling vibration and unwanted gyroscopic forces, saving weight and
‘SUZUKI CLAIMED OVER 150BHP AT 12,300RPM FOR THE 1988 XR74, YET THE ENGINE WAS AS RIDEABLE AS EVER’
reducing friction. Alternative chips for the ignition and power valves gave a choice of power curves, even smoother power and a wider spread of drive, with over 160bhp at 13,000rpm. The V4 was more compact, too, with a narrower 65˚ V-angle. It sat further back in a lighter chassis that saved 10kg and went back to Kayaba suspension, with new upside-down forks. This more responsive and forgiving bike complimented Schwantz’s style and he won six of the season’s 15 races. However, the Texan suffered three breakdowns in crucial races, and although the power gap to rivals had narrowed it was at the expense of a fiercer delivery. The power band was only 2500rpm wide, making the bike very hard to ride and exposing problems in the chassis. Lucky Strike cigarette money arrived for 1990, along with a heap of technology. As power spiralled upwards, Suzuki headed electronic development with a so-called ‘traction control’ system on Schwantz’s new XR76, in which ignition and/or power-valve opening altered depending on gear, revs and throttle opening. Weight was slashed again, so much so that the V4 was under the new 115kg limit at the season’s opening race. The RGV was now a serious contender, and with Schwantz backed by a team-mate capable of getting on the rostrum (Niall Mackenzie) it looked good for Suzuki. Unfortunately, where Kevin found it easy to fine-tune his chassis the previous year, the 1990 bike was difficult to set up for each track. He struggled with it for the whole season, and alongside five wins came five crashes. With a revised 130kg limit for 1991, the XR77 was another complete redesign. It didn’t lack power, but the RGV had lost its previous weight advantage and now became even more sensitive to suspension and geometry. It struggled with grip. And despite previously being ahead on tech, Suzuki were now the only works team without onboard telemetry. Schwantz won five races, but had to ride the wheels off an under-performing bike to end third in the title chase. Things didn’t improve in 1992 – Kevin only won one race in an injury-hit season. It was also obvious from Mick Doohan’s run of early-season victories that Honda had made a quantum leap in taming a viciously powerful, featherweight bike with their ‘big bang’ NSR500 (Doohan looked guaranteed champ, but a crash at Assen wrote off his season). The ‘big bang’ idea was that a closer firing interval helped traction; 500s were hardly short on power, and closer firing gave the tyre more chance to ‘recover’. It was a huge stride forward in making a 170bhp bike into a rideable, forgiving package. Suzuki were first to react to the NSR, perhaps because they experimented with the same idea back in 1978... before rejecting it. Their resulting 70˚ big-bang V4 arrived in May ’92 and was fast and very rideable; only Schwantz’s injury and crashladen season prevented its attributes being truly shown. The final piece of the jigsaw wasn’t new exhausts or fresh geometry, but a change of practice at Suzuki. Their modus operandi had been to decide what
improvements they needed the following year, design a new bike around them – often without back-toback comparison to the old bike – then hope to get it finished in time for a spot of testing before the season. But race engineer Stuart Shenton knew better. Recruited in 1992, he was a former Honda technician who had worked with HRC since Freddie Spencer’s double 250/500 championship season in 1985, and understood the value of linear development rather than sweeping changes. Schwantz desperately wanted more off-season testing, mirroring Shenton’s empirical philosophy, and to their credit Suzuki changed their policy accordingly.
The 1992/93 close season was the first with Shenton onboard, and a very different winter’s testing. “We started two weeks after the final GP of ’92 and ran up to two weeks before the opening ’93 round,” Shenton told me. “It was the most comprehensive schedule Suzuki had ever undertaken. We built on the strengths of the previous year’s bike and produced an improved version, rather than throwing it away and starting again, as they always used to. The chassis we started the season with was almost identical to the ’92 bike, and the only update all season was a new one for Jerez which had a wider range of adjustment.”
Evolution, not revolution, applied to the engine as well. The XR79 version of Suzuki’s twin-crank V4 was closely based on 1992’s big-bang XR78, apart from magnesium crankcases instead of aluminium. This saved 2kg, allowing the team to add weightier, stiffer parts elsewhere – better swingarm bearings, an improved shock linkage. They could add new bits, too, with a quickshifter for rapid-fire gearchanges. More than 165bhp reached the rear tyre at 12,800rpm, a few revs higher than the previous season, yet without sacrificing tractability. The two-stroke would climb from under 7000rpm right up to 13,600 in a seamless, stepless, glitchfree rampage. Now being able to rev 1000rpm beyond peak power also aided useability, saving a couple of gearchanges at twisty tracks like Jerez. Suzuki always knew what its V4 needed, it just hadn’t gone about it the right way; now, thanks to evolution and meticulous testing, the 1993 RGV500 was fast, user-friendly and more reliable than ever. I tested Schwantz’s bike having ridden all its opposition, and it was the most refined, complete and rideable of all. It didn’t quite have the raw power of the NSR, but was a more confident, easier-handling bike. The engine was smooth and linear, yet at the same time so strong and powerful; it changed direction better than rivals, with very neutral steering; and it inspired confidence, in spite of awesome performance. A truly adaptable package.
Schwantz rode a brilliant and controlled season to win the 1993 title, and was a worthy champion. Yet credit must also be given to Itoh and Shenton, whose determination and patient evolution made Suzuki’s RGV500 XR79 the class of the pack.
Pretty? Oh yes. But early bikes were also outpaced and fickle. This is the XR75 in 1989
RIGHT: August 1986, and the breakaway two-stroke fans in Suzuki’s race team reveal their new V4
BELOW: Mitsuo Itoh was a factory GP rider and winner of the 1963 50cc TT
Refined, useable, fast, adaptable and, crucially, reliable – by 1993 the RGV500 was a class act
LEFT: Kenny Irons on the first RGV in 1987. It worked on tight tracks, but lacked speed
Below: Smooth RGV carried Schwantz to a win at a very wet Nürburgring in 1988
Above: Superbike hotshot Schwantz as a wild card in ’87, before Pepsi cash
Suzuki were first to copy the ’big bang’ Honda, and the ’92 bike was fast and rideable
ABOVE: Tab-backed 1990 bike was so light it was under the 115kg class limit
Below: Engineer Stuart Shenton totally changed how Suzuki worked
Engine: 56 x 50.6mm V4, twin pressed cranks, needle-roller big and small ends, single-ring pistons, reed valve induction, flatslide carbs Chassis: Fabricated twin-spar aluminium frame, fully-adjustable Kayaba shock and upside-down forks, carbon fibre brake discs
ABOVE: Massive headstock of XR79 used taper-roller bearings with inserts to adjust steering angle