When Honda created its fabled six-cylinder racebikes in the 1960s, it was pushing back the frontiers of the technically possible. Honda's attitude was that if its engineers could imagine it, they could build it-and it would win. The machines they created were the two-wheeled equivalent of the Apollo 11 spacecraft and the first manned mission to the moon in 1969.
Yet if you're tempted to imagine, from the smug viewpoint of the 21st century, that re-creating one of Honda's Sixes ought to be fairly easy, think again. Imagine attempting to build a replica of NASA's Columbia, the Eagle lunar module and the Saturn pile of pyrotechnics that sent it toward the Sea of Tranquility. Even nearly 40 years later, much of what Honda's race shop achieved remains at the cutting edge of what can be done with metal. That one man attempted to reproduce it in a sleepy English village is staggering. Cold fusion might have been easier.
That man is George Beale. A retired pharmacist and for many years a sponsor of the cream of U.K.-based riders, Beale is better known for the other race replicas he's already built. Among his last big projects was making 1969 four-cylinder GP Benellis from scratch, as easy as building bicycles compared to this job. So why take on something so mind-numbingly complex as the last Honda Six, the 297cc RC174?
Ask almost anyone who can remember the '60s and they'll tell you this was The Bike. The RC174 was an elegant stiletto, good enough to hold back Yamaha's and Suzuki's raucous tide of two-strokes. The unearthly sound it made was like nothing heard before. or since.
Then there was the word of god, otherwise known as Stanley Michael Bailey Hailwood. Many years ago Hailwood told Beale that Honda's six-cylinder machines, in particular the RC174, were the best, most dominant bikes he'd ever raced. The RC174 was so fast, Hailwood declared, "I could have won on it with one arm tied behind my back." If re-creating great machines is what turns you on, then no other project could be so challenging.
For many years Beale's dream of re-creating the RC174 remained just that-a heady dream. Then, some years ago, a distinguished visitor dropped by his Leicestershire home. His name was Sato, director of the factory's own museum, Honda Collection Hall. "I was building a Benelli at the time," remembers Beale, "and he must have been quite impressed, because before he left he asked if I'd consider building a Honda Six. I never imagined I'd get permission from Honda. Later I wrote to Mr. Sato saying I'd love to build a Six, and he replied with permission to undertake the project.
"That was the easy bit. In comparison, the Benelli had been a doddle, using many parts from proprietary suppliers which are still fairly readily available today, such as forks, engine plumbing and bearings, all of which can be the devil to reproduce from scratch. But an old friend, Teruhisa 'Teri' Murayama, already had an original RC174, and I persuaded him to send what he calls his 'pension scheme' to England so I could copy it.
"Later, I went to Japan to visit Teri and Mr. Sato and discuss the project. Sato agreed to let me borrow the missing parts, but unfortunately no drawings were available since even Honda itself had none.
"When Teri's Six arrived, we took the engine out and thought it must be empty because it was so light." Anxiously, Beale stripped it, but everything inside seemed complete. In fact, everything was brand-new. It had never even been started. "This was probably the engine built for Hailwood to race in '68, just before Honda pulled out of Grands Prix," he says. "So it was ideal for us. All the parts were to the very latest spec, and there would be no need to estimate wear to reproduce them."
Among other parts acquired were banks of the Six's jewel-like carburetors. Both the 250cc and 297cc sixes were raced at various times with round- and flat-slide carbs, depending on the power characteristics desired for each race. Beale ended up with a set of each.
Bit by bit, all the original parts came together. All that remained to be done was to re-create these thousands of pieces to the tiniest tolerances, put them together and make them work like Honda did in '67.
Beale soon got a taste of what lay ahead. The first parts made were the oil coolers. If that seems an odd beginning, it was because Honda's own Sixes (the ones it was bringing to its 50th birthday celebration at the '98 TT) had a problem with leaking coolers. When even Honda couldn't get new ones made, Beale was asked if he could help.
"I went to several radiator specialists," Beale remembers, "all of whom said they couldn't match the originals, until I came across Anglian Radiators in Cambridge. They specialize in small production runs, and could source the characteristic frilly finning of the Honda parts from Sweden. Unfortunately it was the wrong size, so every one had to be laboriously cut down by hand with scissors."
In total, 30 coolers were made, including six for Honda, but the process took nine months. "And this is the first bloody bit," Beale thought, beginning to realize what he'd taken on. "I could have just bought an off-the-shelf cooler which would have done the job, but the point was that the replica had to be exactly right-or as near as it was possible to make it."
Yet even that was nothing compared to the engine parts. Most of these were made by JPX, a French company based near Le Mans, France, which specializes in aircraft and high-tech F1 car components. At JPX, the original engine was thoroughly photographed, then carefully stripped, and a detailed assembly handbook created. Every item was measured to the minutest accuracy and X-rayed, and had detailed three-dimensional drawings made-502 in all. Sophisticated hardness testing and metallurgical analysis was conducted on every piece, which revealed some interesting issues. Not a single engine bearing was a standard size, and some of the alloys and surface treatments used were quite unknown to modern science. Soichiro Honda, founder of the company, was also a gifted metallurgist.
In other words, apart from a few nuts and bolts, every single one of the engine's hundreds of components would have to be made from scratch. And not a single one of them, according to Julian Charnol, the man responsible for engine assembly, is anything less than extraordinary. Little wonder JPX regards the RC174's Six as "the most difficult engine we have ever seen ... so full of hidden complexity."
"When they analyzed the engine," Beale recalls, "the pattern-makers were amazed-really impressed by the advanced techniques Honda must have had to make it, which few other companies could have done." Yet at the time it designed the first Six (the RC164 250), Honda had been racing internationally for just five years.
Above all, there was the Six's crankshaft-beautiful, but a bitch to re-create. By '64, Honda had already licked the technology to get the most out of inline-four engines. Adding two additional cylinders might not sound such a big leap forward, yet the implications for engine assembly are huge. The Six's crankshaft is pressed up from 13 components, each no bigger than a domino. Unsupported, it is so flimsy it can be deformed by hand, yet it would have to spin without deflecting at more than 17,000 rpm. Pressing it together with the necessary accuracy-0.01 degree-would require an elaborate set of jigs weighing more than the complete bike; if even one part became slightly misaligned, the entire assembly would be scrap. Ludovic Surcin, designer of the jigs, likened the task to balancing 13 billiard balls on top of each other-and persuading them to stay put.
At one stage it was hoped to use a bulletproof modern crank with split con-rods, but there was simply no room inside the Six's tiny crankcases to accommodate the extra bulk. Consequently the replica retains a design exactly like the original's. With almost no flywheel effect to slow it down, one careless blip of the throttle can send the crank from zero revs to more than 20,000, whereupon it would simply break.
Other details emerged that showed the remarkable lengths to which the Six's design team had gone to reduce the mass of moving components. JPX was astounded to discover three different types of con-rods in each engine, with progressively larger big-end bearings for the rods nearer the center, where loadings are higher. Even 40 years ago the benefit of such a strategy was well-known, but no one else bothered to take advantage of it. Any other manufacturer would have made six identical rods, each able to cope with the highest possible loading. But Honda's obsessive desire to have no component heavier than it need be caused the engineers to tailor each pair precisely for their function.
In the same way, the seven main bearings are also different, ranging from 24mm in diameter at the center to 14mm for the outer pairs. The crankshaft itself runs on carriers bolted to the top crankcase half, which takes all the loads. Thus the bottom half can be made much lighter and flimsier from magnesium alloy.
Similarly, the camshafts (each head has four, linked together in pairs) are barrel-shaped, concentrating their mass at the point of greatest flex, the center, and thus saving weight at their ends. But this in turn means the geometry of the valve gear varies from one cylinder to the next, with different cam profiles. The benefit is tiny, the resulting difficulties immense, yet at every turn Honda went to such obsessive lengths seemingly regardless of cost.
Other than the crankshaft, JPX's biggest challenge was in replicating the Six's tiny but elaborate castings at its in-house foundry. The cylinder block, for instance, is sand-cast using a three-dimensional jigsaw of no less than 29 interlocking sub-molds (known as cores). Casting the heads requires 23, while even the relatively simple sump needs 15.
Even with the very latest computer-controlled technology, machining the major castings was even more complex. JPX's CNC machine-as big as a truck-took several weeks to set up for the job. The machining operation itself took 14 hours and 90 tool heads to machine a single cylinder block. How Honda engineers of the early 1960s did this simply staggers the mind.
The engine is riddled with galleries and tiny oilways, unseen by anything but X-ray, with some only 1mm apart. Sometimes two narrow oilways are combined, saving perhaps 0.5mm in width on a single, larger one. Cumulatively this allows the engine to be perhaps 3mm narrower than it might otherwise-yet another minute but worthwhile return on the work involved.
The tiny pistons are machined from solid, and run in iron cylinder liners. Tolerances are so fine the liners must be dipped in liquid nitrogen before being pressed into the pre-heated block. To reduce internal friction, no oil control rings are fitted, just paired compression rings. As with a few other highly stressed components, JPX had the wrist pins coated with a space-age diamond-like finish, the hardest surface treatment known to science. At the other extreme, many of the new engine's gaskets were simply cut out using a pair of scissors.
Nothing so crude would do for the carburetors, replicas of Honda's round-slide Keihins. The floats are individually modified from those of a current Honda road bike, and even the jets had to be specially machined. Each bank of six cost more than $35,000 to make.
The Six is littered with bearings. All but one or two are needle, ball or roller, which offer less drag than plain bearings. At one stage during the project JPX had one man who did nothing but contact bearing manufacturers all over the world trying to source parts which might fit the Six's bespoke demands. After several weeks he had located perhaps one-third of the team's needs. The rest, including bearing cages, had to be laboriously made from scratch.
The more you delve into the Honda Six's inner secrets, the more you marvel at the skill and confidence of the men who first built it, almost four decades ago. "Compared to this," Beale sighs, "the Benelli was built by a blacksmith."
Secrets of Six
The RC174's complexity made winning simple
Simply put, the 297.06cc inline-six defined Honda's RC174. Without that mighty Wurlitzer of a motor, the bike would barely pique the interest of the most devoted historian.
Likewise, that engine defined George Beale's quest to build an inch-perfect replica of one of Honda's most famous racebikes. From its three sizes of con-rods to metallurgy unknown even today, this totem of Honda's engineering challenged Beale's abilities, his tenacity and his patience. Here are some of the Six's choicest bits.
Japanese multi-cylinder engines may look terrifyingly complex, but such is their inherent design logic that they come apart and go back together with ease. The Six is no exception. JPX's Julian Charnol found that for all its hidden secrets and multitude of tiny parts, the Six was easily reassembled providing sufficient care and time were allowed.
This is not, however, a powerplant suited for garden shed rebuilds. In the '60s, Honda's race shop was as clinically clean as any operating theater, with white-gloved technicians going about their work with fastidious attention to detail. With its Space Age air filtration and controlled environment, the JPX factory is similarly surgical.
Putting the engine together was one thing. Getting it to run as it once had for Hailwood was quite another. "We started with no information at all, no data about settings," Beale says. "At first, whenever we had problems, we had no idea whether it was ignition, carburetion or something else."
After literally years of unrelenting effort, the Six's first dyno run was a bitter disappointment. "It made a pitiful amount of power-as little as 10 bhp," Beale says. "Turned out it was only running on three cylinders. We'd been told by the ignition supplier that we needed only one igniter box and three two-spark coils, which wasn't right. It now runs on two boxes and six separate coils. Later we tried to be clever and map out a full ignition curve. But the thing gains revs so fast that a flat curve is all you actually need, just like the original would have had with its magneto.
"We sorted that, and still got only 33 bhp. The valve guides were too long and obstructing the tiny inlet ports. Julian cut the guides and re-cut the valve seats, and immediately got 50 bhp at 15,000 rpm, and still rising fast. It looks like it ought to give 65 bhp-plus at 17,000 rpm." For comparison this would be 219 bhp/liter, or close to what Honda's RC211V makes.
"All the Sixes you see paraded are running to about 14,000 rpm," Beale says. "That extra 3000 [revs] makes a huge difference to the way it goes-and sounds. And it has to be the noisiest bike ever, even more than the DKW [a shrieking two-stroke nicknamed the Singing Saw]." When George first ran the bike in his garden, a family friend phoned from home to ask who was making "that bloody awful noise." She lives 3 miles away.
"Nobby Clarke, Hailwood's mechanic, says he used to regularly rev the RC174 to 19,000 rpm, even though the factory specified 17,000," Beale says. "Perhaps that's the reason Mike's engines didn't usually last as long as the others."
The man honored with track-testing the Six is John Cronshaw, one of the fastest and canniest classic racers around. His first impression was of the engine's complete absence of flywheel effect. "If you pull in the clutch without staying on the throttle, it just stops dead, even at 10,000 rpm," he says. "So you have to change clutchless. It's like keeping a ball in the air-you have to catch it just right all the time. At present it's a bit more difficult than it needs to be because the carburetion isn't perfect. When it is, it'll be a pretty fast bike."
Cronshaw has paraded the original factory 250 Six. "Compared to the 250," he says, "the spread of power is quite broad, and even the 250 drives right through from 8000 rpm. But it'll take some getting used to not dipping the clutch into corners-you have to drive through everywhere.
"The chassis feels very precise and light. And the engine's so smooth, no vibration at all. It just whistles along, like riding on air.
"With all his talent Hailwood must have been bored out of his socks racing this thing. It was that far ahead of everything else."