Spa-Francorchamps – the fastest grand prix track of them all; a white-knuckle rollercoaster ride through Belgium’s brooding Ardennes forest. Most of the road circuit’s 14.16km were fifth or sixth gear, head squeezed under the bubble, threading the eye of the needle between armco battered and buckled from too many high-speed accidents.

After the Isle of Man TT, Spa was the most dangerous circuit on the GP calendar. The first death in world championship racing was Ben Drinkwater at the 1949 TT; the second was Edoard Bruylant, a month later at Spa. Over the next three decades the circuit claimed so many lives the survivors joked there were enough memorials around the circuit to make a fence.

Barry Sheene’s lap record at the 1977 Spa GP – the last-but-one race before the road course was replaced by a shorter, safer track – was 137.149mph (220.720km/h). That’s an astonishing pace aboard a motorcycle that made barely 120bhp (89kW) and is proof both of huge sustained speeds and steely nerves.

Racing a motorcycle at Spa required pinpoint accuracy and plenty of courage, which is why Sheene always excelled there. Even though he was always anti-TT, Sheene enjoyed the challenge of the Belgian roads.

“Barry liked the place because he knew he had a mental advantage there,” says Suzuki technician Martyn Ogborne, who worked with Sheene for many years. “He knew that you might only get away once with a high-speed get-off at Spa, so he always had a margin of error, though you wouldn’t have known it. He rode the track at 99 percent, but his 99 percent was better than anyone else’s.”

Sheene scored his first GP win in the 125 class at Spa in 1971 and would’ve won the 1976 Belgian GP on his way to his first world title if his RG hadn’t gotten sick. When he returned in July, 1977 he was once again leading the world championship, fending off Steve Baker’s factory Yamaha. Victory at Spa would very nearly put the title out of Baker’s reach.

One of Sheene’s two new teammates in 1977 was best mate Steve Parrish, who had never raced on a street circuit. Sheene showed the youngster what he was in for by taking him for a few high-speed reconnaissance laps in his Rolls-Royce, but nothing could prepare Parrish for the reality.

“I remember it vividly – the main thing was the daunting speed of the place,” says Parrish, who was riding a year-old ex-Sheene factory RG500. “I remember riding through that long right-hander through the village of Burneville, thinking, ‘F*** me, if it goes wrong here… this is just lunacy.’ That corner was like an enormous Gerrards [at Mallory] – well over 100mph [160km/h] with no run-off whatsoever. Then there was that nasty fourth-gear kink on the Masta straight – that was one of those hold-your-frigging-breath-and-get-through-it corners. I suppose the good thing was there wasn’t a lot to remember because most of the lap was just pinned.”

Baker, another GP rookie and street circuit virgin, also made his Spa debut in ’77. “I went round in my car before practice,” says the American. “My first thought was, ‘Oh God, what have I got myself into here.’ It was pretty scary. The thing was that however dangerous it was, you had to keep your corner speed up because with the 500 engine’s power characteristics that made a huge difference in lap time.”

Spa had only one slow corner – the final La Source hairpin, taken at 30km/h. Parrish remembers being so speed drunk that it was very tricky to judge his speed into the corner, “then you’d have an awful lot of clutch slipping out of there because of the ridiculous gearing you were using”.

Sheene didn’t start Spa ’77 from pole. He got stung by a hornet during qualifying and ended up second behind Suzuki privateer Philippe Coulon. In fact the hornet was the least of his problems. These were days of spiralling two-stroke engine performance, which had the tyre companies and chassis makers struggling to keep up. Only two years earlier Sheene had come close to death at Daytona when he was flung down the road at 275km/h after a component failure.

At the end of Spa practice Sheene’s mechanics were shocked when they noticed a groove down the centre of his rear slick and a small pile of tyre debris stuck to the swingarm. The sustained high speeds – his RG was geared for almost 305km/h – had grown the tyre until it chafed against the swingarm, threatening to rip the tyre apart.

“Barry wasn’t impressed when he saw that – it was a shock because it was, ‘Here we go again,’” recalls Ogborne, who believes Sheene’s Daytona crash was caused by the same phenomenon. “The problem with the old cross-plies was that they had so much rubber on them that the tyres would grow far too much. So it was, ‘Oh shit, get all the swingarms out, get the grinders out and grind the chain adjustment slots so we could pull the wheels right back.’”

While the mechanics worked on that bodge, Sheene had a brainwave that he hoped might solve another chassis nightmare. Through Spa’s high-speed direction changes he had noticed when he yanked the handlebars the front wheel didn’t respond accordingly. He realised most of his input was being soaked up by fork twist.

“It was Saturday evening and Barry disappeared for several hours,” recalls Brookman, who was looking after Parrish’s bikes at the time. “He came back with a piece of quarter-inch aluminium plate that had been heated and bent to loop round the forks.”

Sheene had invented the fork brace. “That was the thing with Barry – he was always looking to have something that no one else had,” adds Brookman. “He’d always find someone somewhere and do something a bit different to everyone else. He did the same with Kenny [Roberts] when they were both at Yamaha. That was just Barry.”

Sheene didn’t let tyre worries put him off. “He asked us if we’d fixed the problem and we said, ‘Yeah,’ so he said, ‘Okay, let’s do it,’” adds Ogborne. “It was done on trust – his mind had to be completely free. We had to know that if we lied to him we could kill him, simple as that.”

The race was no pushover. Another RG privateer, Michel Rougerie, led Sheene most of the way while Baker fought back from a sluggish getaway, his piston-ported OW35 a lazier starter than the rotary-valve RG. Meanwhile Parrish found himself embroiled in an epic battle for third with former champ Giacomo Agostini, third factory Suzuki rider Pat Hennen and Finnish privateer Tepi Lansivouri.

“It still stands out in my mind because I’d never slipstreamed so closely in my life. You were inches from the other guys, staring at their exhaust pipes. We were doing these ridiculous leapfrogging manoeuvres – you’d slipstream past someone, then he’d come back past you, then you’d go past him again. And you were doing this with your finger on the clutch in case your engine seized, while looking at the other guys’ tail pipes, watching for the telltale puff of blue smoke that told you their engine was seizing.”

Slipstreaming was such a big deal at Spa that clever mechanics prepared for it. Over-gearing could help a rider take advantage of a tow, while extra fuel was vital in case the rider spent too much time giving rivals a tow. At Spa, Sheene’s RG used an eight-litre auxiliary tank in the seat hump, in addition to the usual 32-litre fuel tank, very nearly twice the fuel load of today’s MotoGP bikes.

“When you got a tow it was a big advantage because not only does it push you forward it pulls the other guy back,” says Ogborne. “But we also dreaded the slipstream because f*** me did the bikes drink fuel when they got slipstreamed.”

On the penultimate lap Rougerie was still ahead. “Michel was giving Barry a real run for his money,” says Brookman. “Then Rougerie’s bike broke, maybe because he’d been towing Barry along, which would’ve made his engine work harder.”

Even with Rougerie out, Sheene’s problems weren’t over. His bike developed a chronic misfire on the last lap – probably due to overheating fuel – and he limped over the line 11.3 seconds ahead of Baker. “I was pretty happy with second,” says Baker. “And I always remember it because when I stopped at the end of pitlane someone had an ice-cold beer for me and that was really good.” Pro-racers rehydrated differently in those days!

Parrish, who ended up a close fifth behind Hennen and Lansivouri, doesn’t recall any hullabaloo about Sheene’s astonishing race speed, “because everyone thought we’d go back next year and go even faster”.

Despite the awesome speeds, Spa wasn’t particularly hard on machines. “Daytona and the Isle of Man were much worse,” Ogborne recalls. “The TT takes your chassis to the cleaners, everything breaks. Daytona would destroy crankcases because the g-forces on the banking would try to push the crankshaft through the bottom of the engine.”

Sheene’s Spa victory was the fifth of six wins during 1977, the most successful season of his career. “Barry was at the height of his powers in ’77 – he could do no wrong,” says Brookman. “He was still up there in ’78, but the bike wasn’t so good. Suzuki went backwards with the stepped RG motor and short frame – he would’ve been better off with a production bike.

“The big thing about Barry was that he was always ballsy. I always thought his bravery was probably more than his ability. This myth about his mechanical ability, I don’t know how much of that stood up, but he was a brave little bastard and he just wanted to win.”

Brookman had a vivid demonstration of Sheene’s willingness to walk the line in 1980, when he was riding production Yamahas. “Barry had got all sorts of trouble, so we went testing at Hockenheim. The short circuit was being used for truck practice, so we got to use the back chicane on the long circuit. Barry had got chattering problems, so he said to me, ‘Martin, will you lie on the ground and watch me coming through the chicane and see what starts chattering first.’ He was coming through there that quick – f***, it scared me! There was no one there, no ambulance, nothing, and Barry was on full noise, right on the limit, and I was lying right where it might be dangerous. I thought, bloody hell, this could end in tears.”

Before the days of data-logging it wasn’t only the racers who needed to be brave – and Sheene was certainly one of the bravest.