Suzuki RS68

Suzuki RS68 125cc V-four

One of the most complex Grand Prix road racing machines of the 60s has been brought out of obscurity in Japan after being hidden away for more than a quarter of a century.

It’s a development of the four-cylinder two-stroke 125cc works racers developed by Suzuki to challenge Yamaha’s supremacy in the class in 1967. Locked away in back room at Suzuki’s Hamamatsu factory with a number of other race machines, it was liberated along with a 50cc works twin by Martin Ogborne for display during the centenary TT celebrations in the Isle of Man in June.

Advert

Ogborne, who works for Suzuki GB and with long-time connections with the Suzuki racing teams, figured he knew where the bike was, having seen it during a factory visit at the end of 1979. "I knew it was there but I never said anything to anybody," he recalled. "The collection of bikes looked more like a graveyard than a museum."

But Suzuki, which was never sentimental about its old race bikes and few of its employees knew about the treasure trove, is now building a museum similar to Honda’s and two mechanics are restoring the bikes for display.

"It’s not known what happened to the other V-four 125cc racers from the 1967 season. Most likely they were crushed; a fate that befell many works bikes. One V-four engine escaped though. It was given to Barry Sheene…"

Advert

The Suzuki brought over for showing in the Isle of Man is an RS68 built for the 1968 season but only displayed briefly that year by works rider Yoshimi Katayama after the factory had quit racing at the end of the previous season.

Supporting Ogborne’s suspicion that the bike had been race prepared before being secreted almost 40 years ago, is its relative ease in firing up during TT week. "But we couldn’t parade it because it was probably using a lightweight sprint chassis that wouldn’t have survived the Mountain course," he said.

It was a development of the tiny RS67 Suzuki that was expected to beat the similar works V-four Yamahas ridden by Phil Read and Bill Ivy. Some records say that its engine developed 42bhp at 16,500rpm and was good for 137mph. But Ogborne says it revved to 17,800rpm with the rev meter red lined at 20,000rpm "and was timed at 148mph."

Advert

But even the RS67 was raced only once. The V-four didn’t appear until the last race of 1967, the Japanese GP at Fuji. British rider Stuart Graham nearly beat Ivy but had to settle for second. "I’m told it was a missile," says Ogborne. "Bill Ivy, who was the Rossi of his day, said to the Yamaha engineers after the race 'You’ve got to do something about that’." But they didn’t need to. Stuart Graham, with the rest of the team, learnt soon after that along with the other Japanese factories, Suzuki was pulling out of the GPs.

It was a cruel blow because Graham, along with team-mates Katayama and Mitsuo Itoh, were promised the V-four earlier in the season but had to continue using their slower twins that were no match for the flying V-four Yamahas.

Blistering period
That Japanese GP was the climax to a blistering period of racing development as 250cc and 350cc four-cylinder Hondas were upstaged by sixes at the end of 1965 and two-stroke twin Yamahas were also replaced by fours. Even the 50cc class was dominated by twins from Honda and Suzuki.

Advert

The 125cc class in 1966 was a three-way battle between Honda, Yamaha and Suzuki, the title holder after Hugh Anderson’s almost clean sweep with seven wins in 1965.

Then Honda wheeled out a new 20,000rpm five-cylinder works bike and Swiss rider Luigi Taveri took the 1966 world championship, one of the three titles Honda won that year.

To match the Honda five, Yamaha had developed its own 125cc V-four, the RA31. And Suzuki’s engineers were also working on a four. But at the end of 1966, Honda announced that it would be pulling out of the lightweight 50cc and 125cc classes to concentrate on the bigger bikes and hopefully help Mike Hailwood wrest the premier 500cc title from Giacomo Agostini on the MV Agusta.

That left the 125cc class as a straight shoot out between Yamaha and Suzuki in 1967. Suzuki’s riders coped heroically with their 32bhp RT66 twins but the 40bhp Yamaha RA31 was much faster, if more fickle.

"The Yamahas were always slow starters," recalls Stuart Graham, 65, who later raced a Suzuki twin in selected non-championship outings before retiring to race cars, "but once they started to chime they caught up. And Read and Ivy were fast riders. That made it a frustrating year. The factory kept promising that the four-cylinder bike was on the way. 'It’s coming, it’s coming, they’d say!'."

Graham had been a successful racer in the mid-60s on British singles and joined the continental circus competing in the Grands Prix on AJS 7R and Matchless G50 singles. He was so successful that when Honda’s Jim Redman was injured in a spill in 1966, Graham was called up to support Mike Hailwood in the 250cc class.

"Redman broke his arm at the Belgian GP and I got my chance," said Graham. "I was third in the 500cc championship. Honda needed someone to help out.

"Honda asked me to join the team. I started on the Honda 250cc six at the Sachsenring for the German GP. The six was the most exotic bike on the scene. Warming it up was an art.

"It was a steep learning curve but there was very close-knit camaraderie in the Honda team. Mike was great with his casual manner and I became integrated into the team. I just 24."

Lightweight classes
Honda’s departure from the lightweight classes at the end of the season left Graham without a ride. It didn’t last long though. Suzuki’s Hugh Anderson, who was retiring, offered Graham a place in the team.

"I went to Japan at Christmas in 1966 to test the bikes and signed for the 50cc and 125cc classes," said Graham.

"The four-cylinder was already under development. It was a square four at first and it was promised for before the Isle of Man TT in June. It was so full of promise. But the team kept running the 125 twins and we couldn’t match the Yamaha V-fours for speed."

Finally, late in the season, the Suzuki team was called back to Japan to test the new V-four.

"I missed the Canadian GP at Mosport – the penultimate rounn – and went to test the V-four in Japan. I got there to see six bikes lined up. They were brilliant and much better than the twin. I tested them at Suzuki’s test tracks at Ryoyo and Fuji and they felt so much better and handled well.

"At the Japanese GP at Fuji I qualified second. My team-mate Yoshimi Katayama had fallen off in practice and had broken a collarbone.

"But the problem was the same as the Yamaha. It took some time to chime on all four cylinders. Then Bill Ivy got away – he was right at the top of his form – and I was a good second. It was a good result and I was really pleased.

"I had a full year’s experience and was looking forward to 1968. We had a bike that would be great in the Isle of Man.

"It was such a tragedy that they decided to quit. We had the bike that we had needed all season. If it had come earlier the 1967 world championship would have been fantastic with well matched motorcycles from both factories.'

It’s not known what happened to the other V-four 125cc racers from the 1967 season. Most likely they were crushed; a fate that befell many works bikes. One V-four engine escaped though. It was given to Barry Sheene, who had raced an RT66 twin to second place in the 1971 world championships.

Barry kept the V-four engine, minus its carburettors and possibly some pistons, for many years until the mid-90s when he sold it along with a number of other Suzuki parts to racer, trials ace and now top restorer Sammy Miller, who rebuilt it as a running replica for display in his museum in Hampshire.

Before it was shipped to the island, I was given the rare privilege to closely scrutinize the RS68 at Suzuki GB’s Milton Keynes headquarters where I was able to cross check its details against photographs taken by works Suzuki racer Graeme Crosby during a visit to the factory, possibly in the late 70s.

Jewel of engineering
The RS68 is a jewel of engineering. Seemingly microscopic alongside modern machines, it was dwarfed by technician Nathan Colombi as he removed the fairing and wheeled it out of the workshop and into the sunlight.

The works racing bikes of the 60s have a style of their own. Designed for high cornering speed rather than today’s point and squirt style of riding, rear wheel traction on triangular tyres was enhanced by the rearward bias of the rider, who perched on the tiny seat and stretched forward over the long, slim fuel tank to the narrow clip-on grips.

Weighing just 209 pounds dry, the RS68 was some 15 pounds lighter – if claimed figures of the day are to be believed – than the RA31 Yamaha it was pitted against. That’s a huge differential: almost two gallons of fuel. But Suzuki’s engineers had stretched technology to the limit to provide a sure championship winner with the maximum usable power and the lowest weight.

The engine used two-stroke principles that had been established after MZ’s works rider Ernst Degner had defected from East Germany in 1961 to join Suzuki. As well as being a handy rider, Degner knew about two-stroke design and Suzuki’s engineers quickly exploited the rudiments of asymmetric disc-valve inlet timing and tuned expansion chamber exhausts.

By 1967, the basic twin-cylinder two-stroke design that had been originally penned by MZ’s Walter Kaaden had been used in 125cc form by Suzuki for three years and was at the limit of its development, and with internal dimensions of 43 x 42.6mm developed peak power of 35bhp at 14,000rpm and with ten gearbox speeds giving a top speed of almost 130mph.

Within the constraints of metallurgy at the time the route to higher power was smaller components and higher engine revs. So like Yamaha, Suzuki switched to four cylinders, grafting two 62.4cc disc-valve twins onto the horizontally-split magnesium crankcases, the upper engine with water-cooled cylinders vertical and the lower having them slightly below horizontal but with a 90-degree V-four.

The pistons and crankshafts were slightly larger than the works 50cc twins, but still tiny with a bore and stroke of 35.5 x 31.5mm, breathing through the disc valves from the first of the VM series carburettors with float chambers concentric with the main jets.

Each engine was geared in the middle of the crankshafts to a countershaft that was in turn geared to the all-metal clutch. Opening up the crankcase would reveal a 12-speed gearbox, necessary because although the peak power was a phenomenal 42bhp, some two bhp up on the Yamaha, the usable range was limited to just 1500rpm. Because of the width of the gearbox, final drive was by another countershaft geared from the centre of the gearbox layshaft to the final drive sprocket and chain.

Mechanically adjustable
To fire the four tiny spark plugs every 3.6 milliseconds two mechanically-adjustable Kokosan magnetos with four high-tension coils were driven from the countershaft on the left side of the motor. Lubrication is by a petrol-oil mixture and oil feeds to the crankshafts through the disc-valve centres.

Despite its width, the V-four engine sits comfortably into the duplex tubular spine frame. It’s also high, the bottom of the crankcase in line with the wheel spindles with the suspension fully extended. Remarkably, the frame is made from welded aluminium-alloy tubing that must have been a feat of argon-arc skills at the time. The swingarm uses rectangular section light-alloy tubing, replacing the round tubing on the RS67, a feature recalled by Graham when he saw the bike at this year’s TT.

Measurements confirm how small the bike is. Wheelbase is a short 50.4 inches with 13/39 sprockets. The seat height is a squat 27.3 inches. Yet from above the engine, because of the width of the gearbox, measures a remarkable 16 inches across the clutch to the magnetos.

Wheels followed common practice, with 18-inch light-alloy rims supporting skinny 2.50-inch front and 2.75-inch rear racing triangular tyres. But the light-alloy brakes look potent enough for a 250, featuring a double-sided twin-leading shoe front of around nine inches in diameter and a similar rear, but single-sided unit.

As racing tools go, the Suzuki RS68 was possibly the sharpest and most wieldy available. Had it been raced as part of the Suzuki team, or had been supplied to the riders with semi-works support, as Yamaha had done, the 1968 season would have offered a fantastic three-way battle, particularly because Kawasaki had also developed a narrow-angle two-stroke V-four. But we’ll never know.

Enjoy more Classic Racer reading in the bi-monthly magazine. Click here to subscribe.

Comments

comments