45mm Showa inverted telescopic forks,
preload,compression and rebound damping adjustment.
Front Wheel Travel
120 mm /; 4.7 in
Vertically-asymmetric Pro-Arm swing arm with Pro-Link,
Rear damper Nitrogen gas-filled damper with reserve tank
Rear Wheel Travel
120 mm / 4.7 in
2x 310mm disc 4 piston calipers
Single 220mm disc 2 piston caliper
16x3.5 in. magnesium alloy
17x5.5 in. magnesium alloy
130/70-ZR16 (Michelin TX11 radial)
Front Tyre Pressure
270 kPa (2.70 kg/cm²; 39 psi.)
180/55-ZR17 (Michelin TX23 radial)
Rear Tyre Pressure
290 kPa (2.90 kg/cm²; 42 psi.)
88mm / 3.5 in
/ 84.6 in.
700 mm / 27.6 in
1435 mm / 56.5 in
785 mm / 30.9 in
360 mm / 44.2 in
130 mm / 5.1 in
223 kg 491 lbs
244 kg / 537.9 lbs
Maximum Weight Capacity
115.0k g / 253.5 lbs
17 Litres / 3.8 gal
Braking 60 - 0 / 100 - 0
12.9 m / 35.9 m
11.4 sec / 197.3 km/h
The Honda NR750 is possibly the ultimate
superbike. It may not be the fastest, and it may not be the best, but it is
arguably the best looking, undoubtedly the most technologically
advanced, and unquestionably the most expensive. What makes the NR750
so special is the amazing high-technology it boasts. It is Honda's way of
proving how clever they are, corporate muscle-flexing by a company who
wanted to prove that they build quality as well as quantity. Space-age
engineering is packed into every cranny of the NR, making it a unique and
fascinating machine. But at £36,500 each (and Honda only built 700 of them)
you'd expect it to be rare. When it costs five times more than the same
company's flag-ship sportsbike, the NR750 would have to be something a bit
out of the ordinary.
What's most special about the NR750 is its
engine. The NR is clever in many respects, but the it is the engine that
sets it apart from any other motorcycle. This liquid-cooled V4 motor uses
oval pistons, no less than eight valves per cylinder and features a
highly sophisticated fuel-injection system. A 32-valve fuel-injected V4 750
is an astonishing feat of engineering, and one which allows Honda to produce
a lot of power from a relatively small package. Each of the two
cylinder banks has double overhead cams. Each piston (they are actually
oblong shaped, but with rounded-off corners, rather than purely oval) has
two con-rods, two spark-plugs and eight valves. Why all this
high-technology? Engines using lots of valves, all opening and closing
quickly, can rev higher than ones with fewer valves. With a rev limit of
15,000rpm and an advanced fuel-injection system, the NR750 produces an
impressive 125bhp (although pre-production prototypes were capable of 140bhp
and the racing bike on which the NR is based was making more than 160bhp).
But there's more to the NR750 than oval-piston technology. The
aluminium-alloy chassis is a work of art, combining strength and rigidity
with lightness, and the NR's suspension is the best money can buy. At the
front the NR features massive inverted Showa i forks and at the back it uses
Honda's fiendishly [clever single-sided swingarm developed for fast wheel
changes in endurance racing. But most breath-taking of all is the
body-work, i an impressive mixture of carbon-fibre and fibreglass that costs
more than the total price of any other mass-production motorcycle. Even the NR's
windscreen is titanium-coated and costs more than most people earn in a month.
The styling of the bodywork is sleek and
seductive, the lines beautiful and the finish higher quality than anything seen
before from a 'mass-produced' motorcycle. As far as performance goes, the
NR is good rather than exceptional. There are plenty of other motorbikes that
will accelerate faster and reach a higher top speed, but the NR750 is one of the
best handling bikes on the road, capable of going from 0-60mph in under four
seconds and reaching a top speed of 160mph. The NR750 is so expensive and
exclusive that most people will never see one, let alone come across one on a
public road. Which is a shame because it is undoubtedly the best looking and
most exciting production motorcycle ever made.
Source of review: Super Bikes by Mac McDiarmid
The Oval Piston: Heart of a New and
To design a 4-stroke, 4-cylinder engine in the
conventional manner would not produce a machine that could out perform its
2-stroke rivals. No, for a 4-stroke engine to generate the same level of output
as a 2-stroke engine it had to have twice as many cylinders as its competitor.
Moreover, 20,000 r.p.m. was the absolute minimum a 4-stroke engine required to
produce superior horsepower.
Increased power meant that the 4-stroke engine would have to consume and exhaust
more of the critical fuel-air mixture. In other words, the aperture of the valve
would have to increase for enhanced intake and exhaust efficiencies. To do that,
the number of valves would increase, also. However, conventional circular
pistons would accommodate only four or five valves. Furthermore, such a
structure would provide no technical advancements, as compared to the time when
Honda was competing in the World GP with its 4-valve DOHC engines. Therefore,
the NR project's new challenge was to achieve "innovative technology," being
more than a mere refinement of the previous technology.
Winning is the essence of racing. Thus, in winning the race, the team could
prove that its technology was superior. Hence, there was no significance in
creating a machine that was not capable of winning. That would lead neither to
technical progress nor to the fostering of outstanding new talent. However, the
Honda NR development team knew that to make a comeback in the World GP meant the
establishment of a training ground for young talents; people who would strive to
improve their skills through the creation of truly great motorcycles. If there
were no chance of winning the race or fostering talent, Honda would be better
off not trying at all.
Honda's answer was the adoption of an oval-piston design. With eight valves
lined up atop the pistons, each supported by two connecting rods, the team's new
4-cylinder engine looked like an 8-cylinder. According to Fukui's calculation,
the engine could potentially reach a maximum speed of 23,000 rpm and output of
130 horsepower. Therefore, the target output was set accordingly, at 130
However, the oval-piston design necessitated an extremely difficult
manufacturing process, in which machining accuracy would be more critical than
ever. Of course, no such design had been adapted for use in a high-performance
racing machine. Nevertheless, the spirit of Honda was never to be pessimistic,
and the team decided it was worth trying as long as there was a real
possibility. In making such a decision the team was well aware of the difficult
path ahead. In order to beat 2-stroke engines, they had to transcend
common-sense thinking and bring in daring new technologies.
The concept for Honda's new engine was finalized in April 1979, and the NR Block
set as its primary goal the realization of an oval-piston engine. The team faced
difficulties right from the start. In fact, they had to prove that oval pistons,
cylinders, and piston rings could actually be made. They also had to find a
manufacturer that could help them do it.
Finally, the team commissioned the production to an associate company, Honda
Metal Technology, located in the city of Kawagoe, Saitama Prefecture.
Development went forward there, but the process was not entirely free of
problems. Since in an oval piston a semicircular curve has to merge into a
straight line, continuous curvature could not be maintained and edges were
created along the piston. This made machining very difficult. Similar problems
were found in the honing of the cylinder's inner diameter, and many hours were
spent in production.
The team members in charge of engine design had their own private concerns, but
spirits were high in the NR Block, where team personnel worked eagerly to prove
that their engine was more than a fantasy.
In July 1978, three months after the start of production, the NR team finally
completed a dual-valve head, 125-cc single-cylinder engine prototype, which they
named "K00." Contrary to the team's concerns, the engine turned properly on the
bench tester. With renewed confidence, the NR Block continued its efforts and
the following October completed an eight-valve head, water-cooled,
single-cylinder engine, the K0. Each day was spent making a prototype, testing
it, modifying the specifications, and testing it again. Repeated testing
revealed that the oval-piston design would cause problems at speeds in excess of
10,000 rpm, due to poor machining accuracy and the loss of durability.
Regardless, the team members knew they could not continue testing
single-cylinder engines indefinitely.
The NR Block was in fact developing a 4-cylinder engine commensurate with the
testing of single-cylinder units. In April 1979, they completed a 4-cylinder
V-engine called the "0X," which was to become the heart of the NR500. During the
bench test, the engine produced 90 horsepower, making it clear that they had not
yet reached their target of 130 horsepower.
The NR Block had also formed a new materials group in order to study two key
problems-machining accuracy and durability. The group leader was to be
Yoshitoshi Hagiwara, then chief research engineer in HGA's Third Research Block,
who had been collaborating with the development team since the early stages of
development. One of the group's key responsibilities was to collect the engine
parts broken during testing and investigate their causes of failure. It was a
tedious task in which it was often necessary to go through the pieces of several
parts one by one and divide them into rings, valves and so forth. The group even
studied new materials such as carbon and complex high-tech materials, along with
enhanced manufacturing techniques that might be used to build parts which could
withstand high engine revolutions. Ultimately, these efforts were fruitful,
producing notable improvements in durability.
It was not just the engine that was
unconventional. To increase its competitiveness, the NR500 also employed a frame
technology that was simply unheard of in the conventional realm of engineering.
Tadashi Kamiya, a research engineer in HGA's Third Research Block who had joined
the NR program in the summer of 1978 as chief of the test group for completed
product, proposed several ideas that he was thinking could be adapted for use in
production cars. One of them was an aluminum frame called the "shrimp shell."
The shrimp shell, which integrated a monocoque structure with the cowling to
form the frame and body, virtually encased the engine, which was then inserted
through the rear like a cassette. The engine was fixed with 18 six-millimeter
bolts inserted at both sides. Although the panel was paper-thin at just 1 mm,
once the engine was in place the frame was able to ensure the required rigidity.
Additionally, the frame weighed just 5 kg, which was about half the weight of an
ordinary tubular steel frame.
The idea, not surprisingly, encountered outright confusion among the members of
the NR Block. In order to convince his colleagues Kamiya created a prototype
model and, the members understood the concept of his shrimp-shell frame.
The second idea involved the wheel. Kamiya thought of adopting a 16-inch wheel
instead of the mainstream 18-inch wheel.
"By reducing the tire diameter," Kamiya said, "we could reduce the machine's
weight by around 4 kg and vehicle height by around 5 cm. The lower air
resistance and smaller disc diameter also contributed to a lower moment of
inertia, enabling the machine to accelerate faster. Moreover, the reduced
frontal projection had the effect of increasing output by several horsepower.
"When I compared the 18-inch wheel with the
16-inch wheel, I asked myself which of the two would cross the finish line first
in actual races, where average speeds often exceeded 200 km per hour, I was
convinced that the 16-inch wheel had greater potential, not simply from the
standpoint of partial speeds at corners but by putting all the elements in
Kamiya also adopted a vertical standing screen to be attached to the cowling,
instead of the regular semispherical type.
"You could call it an invisible cowling," he said. "With this design we can
still achieve sufficient aero-dynamic effect. Since the wind is directed upward
after hitting the screen, the rider is subjected to less wind resistance at high
speeds. Also, the area of frontal projection becomes smaller."
Another idea involved the swingarm and drive sprocket, which were positioned
along the same axis. Because chain length was no longer affected by the upward
or downward movement of the swingarm, there was no need to provide extra play.
This meant an advantage in reducing shock due to acceleration or deceleration,
thus stabilizing the suspension's performance over an entire course.
Kamiya believed that no 4-stroke engine, regardless of its merits, could win
with a frame design based on conventional thinking. Thus, the NR's frame was
constructed from the standpoint of minimizing volume and weight. The staff
sought to create a 125 cc frame capable of carrying a 500 cc engine. These were
just examples of the many unconventional, even outrageous, ideas being
implemented in the new machine. However, they were all based on strategies that
had been calculated to an absolutely meticulous degree.
The NR500 was put to the first test ride in Yatabe, Ibaragki Prefecture, in May
1979. Although the road test brought up problems that the team had failed to
identify in bench testing, these were gradually resolved through refinement of
the engine in repeated tests at Suzuka Circuit and on the course at Tochigi. The
NR500 became more complete with each passing day, and soon it would be ready for
its first World GP event. Due to a significant delay in the NR500's overall
development schedule, though, its comeback had to be pushed back to the British
Grand Prix, which was to be held at Silverstone on August 12.
The NR500 was at last completed in July 1979. Equipped with a 4-cylinder
V-engine and 100-degree cylinder banks, the machine had a maximum output of 100
ps at 16,000 r.p.m.
The NR team had finally made it to England,
where the machines were receiving their final tuneups in preparation for the GP
race. At the same time, Yanase was making various arrangements in order that the
team might concentrate on the race free of hindrances. Thus, in addition to
setting up the bikes for optimal performance on the track, there were many other
things that had to be done for each race, such as arranging transportation and
accommodations for the many staff members involved. The World GP, often referred
to as the Continental Circus, had most of its races in Europe. Therefore, while
it was possible to develop the motorcycles in Japan, it was impossible to manage
the races from Japan. The distance was simply too great.
Yanase rented a warehouse in Slough, an English town near Heathrow International
Airport, as their team's base of operations in Europe, while in Britain
additional preparations were underway through a company called HIRCO (Honda
International Racing Corporation). Honda had established HIRCO in December 1978
as a joint venture with Honda UK for the management of all racing activities,
including competition in the World GP series.
Honda's riders for the 1979 season would be Mick Grant and Takazumi Katayama,
the latter having competed in the 1977 World GP series as a privateer, where he
ultimately won the championship title in the 350-cc class.
For their part, the NR500s kindled great expectations upon their appearance at
Silverstone, portending awesome performance with their original engine design
and sleek styling. However, those expectations were mercilessly shattered in the
qualifying round. These bikes, which were still in development, barely performed
well enough to get through to the final. Even then, Grant fell at the first
corner following the start and quickly retired. Katayama also retired after
several laps due to ignition problems.
Though they had not expected a win in their very first race, the NR team was
deeply disappointed with the outcome of their efforts. The NR500s were brought
back to Japan, and improvements were made to further reduce weight and increase
output. However, those really were not the fundamental solutions that the
project team had long sought.
Harsher realities awaited in the French GP, the twelfth race of the 1979 season
where both machines failed to qualify for the final, meaning that no results
whatsoever could be garnered from their presence. However, the team could not go
back to Japan without data, after having spent so much time and money in
preparation for the French event.
Therefore, the staff of the NR Block flew to England, and with help from HIRCO
tested the NR500s at Donington Park. The test was a fruitful one, in which new
areas of possible improvement were identified. However, there was no improvement
in speed, and the machines were still running two seconds behind the lap record.
In the world of racing, where one-hundredth of a second determines the winner,
two seconds was just too great a handicap.
Having finished the 1979 season with
disappointing results, the NR500s had two major problems that were considered
unique to 4-stroke engines.
First, was the factor of extreme engine braking. When development began, the
team viewed engine braking as an advantage, believing it would assist in overall
control of the bike. On the contrary, the engine braking caused the rear wheel
to hop. To counteract it, the team developed a back-torque limiter with a
built-in, one-way clutch so that the wheel would spin when the force applied to
the wheel exceeded a certain level. This methodology was later incorporated in
the VF750F, making it the first production bike to be equipped with a
Acceleration was the second problem. It simply did not provide the necessary
subtlety of control. The ability of the engine to generate ample low-end
torque-a characteristic of 4-stroke engines-also made cornering control
difficult, resulting in the loss of time. During the 1980 season the team
experimented with throttle pulleys based on various shapes, but as yet there was
Weight was another area in need of attention. Although the first 0X engine was
lighter than the average 2-stroke engine, weight gradually increased as
durability improved. Before long, the engine had put on as much as 20 kg. The
development team conducted an exhaustive review of materials, going to titanium
and magnesium in order to achieve weight reduction. However, the new material
combination was quickly copied by rival teams, leaving Honda with no advantage
in that area.
The shrimp-shell frame, which had so greatly contributed to weight reduction,
also had a drawback. Because of its cassette-type mounting structure, the engine
had to be removed from the frame in order to perform maintenance. This made it
difficult for the engineers to achieve optimal settings within the limited time
allowed in the qualifying runs. Accordingly, the team decided to adopt a pipe
frame to the machines, beginning in 1980. At the same time, the wheel size was
changed to 18 inches.
Ultimately, the problem with the NR500 was that so many new technologies had
been introduced that its potential for completion had been compromised.
Realizing this, the NR Block prioritized problem areas, placing the top priority
on refining the engine. This, they believed, was the most fundamental problem of
The new and greatly improved NR500s competed in an international race held in
Italy. Although it was not a World GP race, Katayama was able to take the podium
with a third-place finish. He also put up a good fight in the final round of the
British World GP, held that August. The fifteenth bike to pass the finish line,
his machine was the first NR500 to finish a GP race. Moreover, Katayama made a
strong showing in the West German Grand Prix, finishing in twelfth place.
The 1980 season, however, closed with just two events in which Honda's NR500s
made it to the final round. Still, the machines were making steady progress, so
it was still possible to build a point total and finish the season in tenth
place or higher. However, the reality was that they were still trailing the
2-stroke machines by 10 or more horsepower. Therefore, even if the NR500s could
advance in the standings, they did not have what it took to win a GP race.
Yanase recalled a sentence in the plan document he had received in December
1977. It read, "Become the world champion within three years." He knew that 1981
would be the final year in that attempt, so there was not much time left.
The oval piston engine underwent further
improvements in order to reduce its weight, enhance output, and improve
durability. The improved engine intended for the 1981 season had a smaller body,
made possible by dropping the V-bank angle from 100 degrees to 90. Moreover, it
had a maximum output of 130 ps at 19,000 rpm. Therefore, beginning with the 1981
season, Honda decided it wouldn't just compete in the World GP, but that it
would also enter the All-Japan Championship Series. Honda made the decision to
refine its NR500s more rapidly through participation in more races, hoping to
build winning machines as quickly as possible.
In the second race of the All-Japan Championship, held at Suzuka Circuit in
March 1981, the two NR500s ridden by Katayama and Kengo Kiyama both fell and
retired. However, they had demonstrated considerable tenacity during the race,
advancing to a point just behind the top group. In the next race held at Suzuka
in April, the team saw one of its NR500s finish in fifth place. By this time,
the NR500s were performing at levels equal to those of their 2-stroke
Yoichi Oguma, the chief research engineer from HGA's Second Research Block who
had joined the NR project in 1981 and became the first manager of the Honda
Racing Team (HRC) the following year, had one vision: "Tactics and strategies
also are important in winning the race. Honda is so preoccupied with the
performance of its machines, but we can't win unless the machines, the riders
and the team work as one."
This was a conviction that Oguma, a former All-Japan champion in the 125 cc
junior class, had acquired through his own experience. Reflecting on that
belief, the Suzuka 200-km Race-the sixth All-Japan race held in June 1981-was
run under his careful supervision, according to a calculated strategy.
Any 2-stroke engine running a distance of 200 km, or 34 laps of the Suzuka
Circuit track, will require at least one pit stop in order to refuel. That means
approximately 10 seconds in the pit area. Considering that the bike must
decelerate to enter the pits and accelerate again on its return to the course,
nearly 20 seconds must be given up. Oguma's strategy was to let his machines run
the entire race without a fuel stop by making use of their higher fuel
efficiency, which was of course the advantage of 4-stroke design. According to
his calculations, the NR500s would save around 0.6 second per lap by eliminating
the fuel stop.
The race was carried out according to plan. While the rival machines were making
their fuel stops, Kiyama's NR500 gradually advanced, eventually passing the
leader on lap 23. It was the first time an NR500 had led a race. What's more,
Kiyama maintained his time, leading the race lap after lap. Coming out of the
last corner first, his NR500 kept its lead and took the checkered flag. Three
years after the start of development, the NR Block and its NR500 had achieved a
The team was again victorious in July, when Freddie Spencer rode his NR500 to a
first-place finish in a five-lap heat race held at Laguna Seca in California,
which doubled as the qualifying round for an international race. It was with
these victories that the NR500s were established as contenders in the ultimate
challenge: to win a World GP race.
It was, however, still quite premature to assume that victory in a World GP
event was theirs for the taking. That was too high a mountain to climb. After
Katayama's thirteenth place finish at the first Austrian Grand Prix in April
1981, the riders continued to retire from subsequent races. The 1981 season
ended without any point total for the Honda team.
Hence, the promise to become the world champion within three years was broken.
The NR Block had found itself at the crossroads of victory and defeat, survival
Here’s a bunch of pics from the Rayong
Province, Thailand. Two friends are out riding their bikes, but not just any old
bikes – we’re talking Honda VTR1000 SP2 and the
Honda NR750! ‘Given its year of manufacture
, the NR still feels fresh and capable, though a tad heavy. It was happy
to cruise at around 140km/h with spurts of up to 200km/h. Brakes are sharp and
the chassis is more stable than flickable. It isn't an RC30, let alone a modern
sportsbike, but it’s an enjoyable bike to ride on a Saturday morning cruise and
its able enough that you don't need to make excuses for its performance in the
company of the SP2,’ says the guy who owns the NR.
‘The SP2 has had quite a bit of work done to it and felt taught and lively
compared to the NR. They are both
Hondas and both have RC stamped on their frame
but beyond that, they are as different as chalk and cheese. Without wanting to
put the NR down in any way, the SP2 is the more involving and sportier bike of
the two to ride and by quite a margin. However, it has to be factored in, that
the main factor to riding the NR is that you don't really want to be riding it
on the limit. There is always a fear of dropping the NR or even a stone flicking
up off a truck as you passing it and causing damage to unobtainium paintwork or
screen,’ says the NR owner. ‘To a certain extent, with time in the saddle, you
get to relax and enjoy the experience. The NR’s retro/modern digital speedo (or
is that modern but retro now?) and all the various dials on the dash keep you
entertained and the bike is comfy and ergonomic. In addition, once you've
arrived, you get the added bonus of having an extra view of the NR to admire
when hanging out on the beach. The NR gets attention wherever it is parked. Even
non bike enthusiasts take a peek at it,’ he adds.
‘You can see just how lardy the NR is. You kind of sit inboard and the bulk is
behind and in front of the rider. However, a blindfolded person would think the
NR is lithe, from the riding position alone. It is surprisingly narrow with
hardly any splaying of legs around the tank. Reach to the bars is natural and
sporty while the screen – iridium coated and looks fantastic – is low for most
people. Between the NR and SP2, the difference is in facial expressions. The NR
is smiley, the SP2 looks almost startled in comparison,’ says the NR guy.
‘The NR’s carbon air-ducts don't actually function though they do hide the
screen brace. Seat is made of seude and is definitely not fake. Seems a strange
choice for what is essentially a sportsbike but looks and feels good. The side
ducts in the seat cowling are functional and the exhaust is otherwise fully
enclosed – it gets pretty hot despite those air ducts, but no problems so far.
The lower cowling, in carbon, is pure sex. Front forks are massive for the day,
at 45mm. They are fully adjustable of course. The twin spotlights mounted in the
fairing give the bike a unique frontal presence. Swingarm was the sexiest seen
on a production bike until the MV F4 was launched. The frame has some special
(some say, titanium) coating and is easy to keep clean and shiny. Swingarm is
actually lacquered so you need to be careful with solvents and chips. Still
looks good after 18 years,’ says the NR owner.
Look good, it certainly does. An NR may not even be able to keep up with a
modern-day CBR600RR, but for its sheer Honda-ness, technology-porn that’s
unrivalled to this day and mega exotic-ness, the NR was, and continues to be,
right on top. How we envy people who actually own a Honda NR... :-)
Honda produced just 300 units of the NR and that was
back in 1992 and yet, for us, that bike remains one of the most intriguing,
deeply fascinating motorcycles ever built anywhere in the world. Some of that
fascination is down to the NR’s oval-piston engine, of course – the NR’s
massively complicated four-cylinder 750cc engine had 8 valves per cylinder and
two conrods per piston, which allowed the engine to function as a V8.
It cost US$50,000 back in 1992. And it really
doesn’t matter that with 125bhp at 14,000rpm, the NR engine’s output doesn’t
really look anything special today, when compared to modern-day 750cc
“When I look back at it, I’m not sure if we were experimenting with cutting-edge
technology or obsessed with foolish ideas,” says Toshimitsu Yoshimura, speaking
to Inspire magazine. “We didn’t think much about whether the engine would
actually turn over or even whether it would be practical at all. We weren’t
worried about those things since we just wanted to make it work. To create
anything, you must put your heart and soul to it. The development of oval piston
engines impressed that upon me, as well as on the other young engineers,” adds
Toshimitsu, who was one of the engineers who actually worked on the development
of the Honda NR’s oval-piston engine.
Toshimitsu’s story is taken up by Makoto Hirano, an R&D engineer who used to be
in charge of engineering and production at Honda. “The oval piston’s development
started from the racing scene. At that time, during the 1970s, across the world
people were starting to be aware of the problems related to pollution. Therefore
Honda wanted to try to reduce engine emissions by building a four-stroke racing
bike. In those days, the other manufacturers were only building two-stroke
engine bikes,” says Hirano.
“The idea of the oval piston came from the need to reduce piston friction in the
four-cylinder engine… we had to make more cylinders in the four-stroke-cycle
engine and an extremely short piston stroke. So we built a ‘one-cylinder’ which
is equal to two cylinders. Which means, to build an eight-cylinder in order to
fit the four-cylinder rules limit on the race,” says Hirano. “There were no
suppliers who could collaborate with us to make oval piston rings. They said,
‘Oval piston rings won’t go mainstream. Furthermore, we have no special
equipment.’ But we strongly requested them many times,” he adds.
“Incidentally, the VTEC (variable valve timing and lift electronic control) was
invented during that period. During development of the oval piston, we tried to
have the eight valves to four valves. We studied about losing the engine’s
‘startability’ to improve the combustion and to increase the horsepower in the
middle-to-low rpm area. A test engineer found this by coincidence and this
innovation led to the idea of the engine of the CBR400. If Honda had given up
the oval piston development, there wouldn’t have been any Honda VTEC,” says
“Honda’s oval piston had extremely high performance alongside that of the round
piston engine. Therefore the race regulations at that time prohibited using the
oval piston, first in Formula 1 and then in MotoGP. So Honda could not use this
technology and could not feedback to the production. But what I can say for sure
is that only Honda could develop this technology. The oval piston proved Honda’s
highly advanced technology to the world. It was an epoch making technology,”
Source: LCR Inspire
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