The Sheene Machines (Part 1/2)

Published: 20 August 2016

He liked his handlebars set wide and preferred aluminium crankcases, Heron Suzuki mechanic Martyn Ogborne reveals the secrets behind Barry’s winning bikes 

We all know the story of Barry Sheene’s 500cc Grand Prix world championship success in 1976 and 1977 – at least from the rider’s point of view. But the rider is only half the story. Sheene also needed the right bikes underneath him to make it happen and these are the two machines that took him to his two world titles. They’re currently in the UK on kind loan from the Sheene family residence in Australia and MCN was given exclusive access not only to the bikes but also to the man who made them work – Bazza’s legendary chief mechanic, Martyn Ogborne. We spent a morning poring over Sheene’s RG500s in minute detail with the one man who knows them inside out.

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MCN: Are these bikes exactly as they finished the 1976 and ’77 seasons or did Barry do a lot of restoration work on them?

Martyn Ogborne: No, these bikes are exactly as they were when the seasons ended. I can tell by looking at the smaller nuts and bolts because a lot of them are aluminium or magnesium and used to wear away. The lifespan of each of Barry’s bikes was only about three months – or three Grands Prix – that’s all they were intended to do. Then they’d get a new engine, not because there was anything wrong with the one he was using but because Suzuki would have come up with an improvement. So we’d remove the old square-four and use it for UK national races.

We always carried two or three spare chassis to GPs but didn’t really need them unless Barry had an off. For example, if he broke a footpeg we’d change the whole chassis anyway because the footpeg was bolted in. 

MCN: Do these bikes run?

MO: No. They could be made to run but it would take a lot of work. You’d be looking at six weeks to prepare an engine alone because everything breaks over time. These bikes are almost 50 years old but they had a shelf life of just 90 days. They weren’t designed to last because they didn’t need to last. But it’s nice that they’re so authentic. When we brought the 1977 bike over for Vic Reeves to ride at Oliver’s Mount for a TV documentary we had to change everything – the engine, the swinging arm, the suspension. Only the chassis and bodywork were original.

MCN: What are the origins of the Suzuki RG500?

MO:  The RG500 came along just six years after the Japanese manufacturers were effectively banned from Grand Prix racing because their technology was becoming so advanced (most manufacturers pulled out of GP racing between 1968 and 1971 because of technical restrictions). In 1968, Suzuki was all ready to go with two-cylinder and three-cylinder 50cc bikes, and a V4 125 and 250, but overnight the FIM banned that technology because the smaller European factories like Bultaco and Minarelli were complaining that the Japanese had an unfair technological advantage. It was a joke. There were also rumours that Honda had a V8 too, which was really scaring the smaller factories, but it turned out they didn’t. So in 1974 Suzuki could have gone with a V4 but they’re incredibly expensive to engineer so they went for a square-four which they had already tried in a 250. Basically it’s four rotary-valve, 125cc engines put together. The 250cc square-four had one cast block of four cylinders – like an Ariel square-four – but the RG500 had four separate cylinders. It came about very quickly. Suzuki drew it in May 1973 and it was ready for its first run by October – and then the public saw it for the first time in 1974. 


MCN: What was the RG500 like to work on?

MO: They were generally very good but the big drawback was changing any ratio in the gearbox. You had to take the whole engine out, which took about two hours to do. At that time Suzuki didn’t have the technology to allow us to have a cassette-style gearbox – that only came later. The original 1974 RG500s had seven and even eight-speed gearboxes but by 1975 that was reduced to six. The power wasn’t very useable. Maximum power was at about 11,200rpm but it only came in at 9800rpm so it was a very narrow window and came in with a hell of a kick.

As the engine was developed we managed to bring the power in at much lower revs and that’s when we needed different gears. Grand Prix bikes were getting so fast that the race circuits were changing as chicanes were added to slow things down. The MV Agustas of the previous few years weren’t that fast and you only had a couple of riders with factory machines, but once Suzuki and Yamaha started to produce production racers the whole grid was doing 180mph everywhere. At the old Spa circuit in Belgium Barry was holding the bike flat-out at 180mph for most of the lap (Sheene still holds the fastest ever lap by a GP bike at 137.15mph, set on the ’77 bike you see here) so you can see why the organisers started putting chicanes in. And because of all the new chicanes, we suddenly needed new gearbox ratios to get drive out of them. 

MCN: Was the RG an easy bike to set up from circuit to circuit?

MO: The best base setting was the previous year’s settings (once the team had a year under its belt) but when we went to a new circuit, like in Venezuela, it was bonkers. It was great for Suzuki because we won it five years running while the Yamahas were falling apart and everyone asked how we did it. It was regularly 53°C there so I used to wheel the bike outside to warm it up. By the end of the race the bikes were so hot – about 140°C – that Barry would only be using four gears because the bike had lost all of its power. The secret was to build bigger radiators but Yamaha never wanted to do that because it would slow the bike’s top speed down. But when you were only using four gears, that didn’t matter. I’d look at the Yamaha radiators in Venezuela every year and think, “Well, that’s you guys finished!” They were half the width of ours.

MCN: Did Barry find the RG500 to be a neutral-handling bike?

MO: After having an 18in pin put in his leg after his big Daytona crash in 1975, Barry taught himself to ride without crashing because if he’d crashed with that pin it could have shattered his whole thigh bone. Not many guys would go into a Grand Prix thinking, ‘the main thing is not to crash’ but he had to teach himself that because he couldn’t afford a get-off.

So, yes, he liked the bike to have neutral handling but once all those chicanes started coming in he had to change that. He struggled with chicanes because he couldn’t use his legs to weight the pegs like the other riders. He had the pin removed in 1977.

MCN: What are the Suzuki code names for these bikes?

MO: Both of these bikes are XR14s. XR means ‘experimental racing’ and the 14 is just a number that’s not necessarily in sequential order. So, for example, XR3 could have been a motocross bike. We dubbed the 1977 bike an XR14A simply because there was a slight change to the rear of the chassis (under the seat) that looks like the letter ‘A.’

MCN: The bodywork is the most noticeable difference on the two bikes. What were you trying to achieve with the changes?

MO: We started experimenting with different cowlings as speeds increased. Streamlining was almost an afterthought in those days but it was really important when a rider was being drafted. Barry would see his revs drop as the rider behind sucked him in. That meant the rider behind could roll of the throttle slightly and have some extra rpm at the end of the straight to overtake. It played havoc with the fuel consumption of the leading bike. We’d normally run 32 litres of fuel but at places like Spa we’d run 37 litres by storing more under the rear seat unit. We found that having lower screens helped: big, floppy screens were not the key to aerodynamic efficiency.

 

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