The Dakar Rally, currently staged on the South American continent, was formerly known as the Paris-Dakar Rally, raced on the African continent, from its inception in 1979 until 2008.
The Paris-Dakar Rally was founded by a Frenchman, Thierry Sabine, who had raced in rallies in Africa. Sabine had also raced in the first Paris-Dakar Rally (called the “Oasis Rally” at the time) which he had organized. Many participants of the early rallies were French, reflecting a national preference for long-distance endurance races.
At the time, Paris-Dakar Rally competitors left Paris, France on Christmas Day to cover approximately 12,000 km (later extended) over 20 or so days. Most of the course was set in harsh conditions, including the uninhabitable Mauritanian desert and the Tenere desert, barren in all directions for hundreds of kilometers.
As a result, more than half of the participants did not complete the rally, and some even lost their lives. Riders would have to cross politically unstable regions on occasion. Being called “the world’s toughest race,” from its beginning, was no exaggeration.
The event gained wide recognition in Europe as a motor sports event marking the beginning of the new year. In France in particular, it gained popularity rivaling the World Grand Prix (currently MotoGP) and the 24 Heures du Mans.
Around the same time, more automobile and motorcycle manufacturers worldwide entered the rally to promote their products' performance and appeal.
The Yamaha XT500 claimed victories for the first two rallies, after which the BMW R80 won in 1981. Honda debuted in the 1981 event. At the request of Honda France, Honda competed on the XR500R (550cc), with the help of the Asaka R&D Center (currently the Motorcycle R&D Center). Although finishing 6th that year, Honda went on to conquer four consecutive beginning in 1982.
French racer Cyril Neveu rode the XR500R to victory. Neveu was also the leading rider for Yamaha’s previous two wins, and was an outstanding desert motorcycle rider.
Even Neveu’s riding, however, was no match for the production motorcycle BMW entered the following year. The 800cc flat-twin engine’s power was far superior to the single cylinder engines that were mainstream at the time and, despite its weight, its lower center of gravity also gave it an advantage.
BMW’s riders, including Neveu’s rival African-born Frenchman Hubert Auriol (disqualified for arriving too early in the second rally), and former World Grand Prix Motocross champion Gaston Rahier, achieved the spectacular feat of three consecutive victories from 1983.
BMW had achieved an astounding four victories out of the seven rallies they had competed in up to 1985. In contrast, the Honda France Paris-Dakar team was unable to beat the fast BMW machine, and also played second fiddle to Cagiva’s machine, with an L twin cylinder making it first appearance in 1985.
The Paris-Dakar, through the BMWs, had entered into the high-speed age. Twin cylinder machines, while significantly heavier than their single cylinder rivals, could quickly reach maximum speed, leading to the evolution of high-speed racing. The rally itself shifted from a mainly amateur field, to battles between factory teams “going in for the win.”
Honda was, of course, the strongest contender for BMW. By Honda France’s strong request, the HRC Project Team was formed in the autumn of 1984 and, with the aim of “winning the 8th rally in 1986,” the development of a machine exclusively for the Paris-Dakar Rally begun.
The development team assembled their best and the brightest talent with experience in road, motocross, endurance and dirt track racing. On visiting their first rally in 1985, Honda had their first taste of the Paris-Dakar for the first time.
With terrain including desert, rocky stretches, loose gravel dirt, savannah and paved roads, temperatures ranged from below freezing to above 50℃. The longest day covered 800 km in SS (special stages), not including the liaison (or untimed) sectors. In most cases, the gasoline contained dirt and impurities, with unstable octane concentrations.
The development team were shocked at the highly demanding conditions, for which they had to deliver the highest performance as well as durability and maintainability. The requirements for (or the concept behind) a machine that could aim to win under these conditions included:
1) Light-weight and compact (affecting all aspects including driving performance, rider fatigue, and durability)
2) Maximum speed of 180 km/h (cruising speed of approximately 150 km/h)
3) Is not demanding on the rider (flat output characteristics essential)
4) Does not break down (mechanical issues can be life-threatening to riders)
5) Good maintainability (ideally no maintenance needed)
6) Focused on high-speed stability (high-speed cruising in the desert is critical to win)
7) Fuel efficient (Target fuel consumption during design stage was 9.1 km/L. As a rule, cruising distance is 450 km (+ 20%))
8) Concentrated mass (concentrated as close to the vehicle’s center of gravity as possible)
The engine required flat output characteristics between 3,000-8,000 rpm with high-power and torque, with a minimum durability of 4,000 km (at the time, a total of three engines could be used.) As a result, the V twin engine with 45-degree bank angle and 90-degree crankshaft angle was selected.
This layout could cancel primary vibration, and was advantageous for ease of use, rider fatigue, and durability. The concept was based on the expertise gained from the dirt track RS750D's V twin engine (same specifications), which was developed slightly earlier.
Moreover, the engine was as slim as a single cylinder engine, leading to advantages in chassis layout as well. In order to exploit these characteristics, a unique design was adopted for the Paris-Dakar Rally machine, involving the combination of a needle roller bearing with the monolithic crankshaft to minimize width.
A connecting rod with a partitioned large end was used for the monolithic crankshaft. Plain metal is normally used for this section, as the bolted section tends to lose precision (roundness) in the assembled area.
For a machine to race in the Paris-Dakar Rally, however, a needle roller bearing, resistant to momentary oil shortage caused by body inclination and entry of dust, is a must.
As this requires the roundness of the large end be secured, the fracture split connecting rod (monolithic molded connecting rod is split apart) was employed, enabling precision in the assembled area (this was used in entries after the NR500). As a result, engine oil capacity itself was also able to be controlled.
The completed water-cooled SOHC 4-valve V-twin 779.1cc engine had a bore/stroke of 83 × 72 mm, with a maximum output of approximately 70ps/7000rpm. The chassis that housed this engine was also novel with a creative structure.
This machine also pioneered the now universal large cowling and large tanks for big off-road models.
The giant split fuel tanks on the left and right were installed down the sides of the engine to lower the center of gravity. The space below the seat was also utilized as a fuel tank, securing a total capacity of 59L.
Each of these three tanks had independent feeding systems, so the motorcycle could still run even if one tank was malfunctioning. The tank under the seat was rubber, while the side fuel tanks were made from Kevlar (aramid resin) on the outer sides, which also offered protection from damage or fuel leakage caused by falls.
The bike had an otherwise orthodox structure with a steel pipe frame, 280 mm stroke front forks and Pro-Line rear, kick and cell starter and chain drive (large jumps were impossible with a shaft drive), which secured superior maintainability while thoroughly eliminating risk.
The machine, which was designed for reliability and ease-of-use rather than extremely-tuned riding performance, lived up to its concept in local test runs in the Tenere Desert and other areas. It was named the NXR (the French called it the “neuksar”) and was sent to France to compete in the 8th Paris-Dakar Rally, in 1986.
Shortly after that, the spare engine, in Japan, suddenly experienced problems with stud bolts suddenly blowing off. The crank case had been made of magnesium alloy in order to reduce weight, and it appeared that the parts where the bolts were mounted were not strong enough.
A new aluminum alloy crank case was hurriedly built and flown over to France. This turned out to be the only instance of unanticipated issues.