Honda Gold Wing: 50 Years of Touring Greatness

Honda’s Gold Wing, the acknowledged pinnacle of technical touring, is a motorcycle whose design features are founded in reason rather than tradition. Although for years the origin of GL1000, the first Gold Wing, was associated with a six-cylinder research project code-named “M1,” engineer Toshio Nozue has said that “Project 371,” which would become the GL, was in fact unrelated to M1. Nozue said, “M1 was built as part of basic research for the future, but it was never intended to be mass-produced.

“When developing the GL1000 there was absolutely no attempt to copy or utilize the research results.”

Related: Tour de Force: Riding 50 Years of Honda Gold Wings

GL1000 was planned to cover long distances in comfort and silence. Power would come from a flat, four-cylinder-opposed engine making peak power of 80 hp at 7500 rpm and peak torque of 61 lb.-ft. at 5500 rpm. Those numbers, combined with a fairly high planned weight, suggested the GL was designed to combine the above virtues with strong performance.

To be easy to ride, a wide torque range was essential. To make the engine reliable, performing well regardless of weather or season, liquid-cooling was chosen—despite Mr. Honda’s special affection for air-cooling. So heavy a machine would feel lighter and be more manageable if its weight was placed low. Therefore a flat engine, with its cylinders opposed rather than upright, was chosen. Each opposed pair of pistons operated in “boxer” fashion, always moving in opposite directions, balancing each other’s shaking forces. To produce propulsive smoothness, it fired at even intervals.

Shaft drive was chosen, giving the rider no more reason to think of GL1000′s final drive than an auto’s driver has to ponder the differential.

Because the induction system could only be placed above the engine, the fuel that would otherwise have occupied that space was pushed rearward, under the seat, where its lower position made the bike lighter to handle.

Four cylinders were chosen because the greater length of a six or eight would push the rider back, away from the normal location of a motorcycle’s controls.

Concepts radical at the time were prototyped and tested: fuel injection, automatic transmission, and automatic centerstand erection. At its 1975 intro at the Cologne show people didn’t quite understand what it was.

Gold Wing soon found its role in the US motorcycle market of 1976. Its smoothness, its reliability, and its ability to easily cover long mileages heavily loaded “catalyzed the growth of motorcycle touring in the USA.” Riders soon customized their Wings to this purpose with bags, windscreens, backrests, and other comforts. This fundamental change of Gold Wing’s role was somewhat at odds with its torque delivery and suspension. Its peak torque up at 5500 rpm conflicted with touring riders’ preference for max torque at highway cruising rpm of 3000, where it was so useful for passing or to climb grades without need to shift down.

It was an odd mixture of traits: the firmish and sportbike-like suspension, torque high up the rev scale, but with a tour-compatible 28 degrees of steering rake and 4.7 inches of stability-ensuring trail. Compare those numbers with the sporty CB750′s 27 degrees and much shorter 3.7-inch trail.

There were few production changes before 1978, when measures were taken to fatten torque farther down the scale: smaller 31mm carbs and shorter valve timing. Honda’s product planners were on the job, noting how riders were transforming their Gold Wings. At the end of GL1000 production, factory-installed saddlebags and top trunk were optioned. This constant addition of conveniences and amenities would drive weight growth throughout Gold Wing’s development.

GL1100, the 2nd gen Gold Wing, received a second torque boost with another carb size reduction. To increase stability, the rake became 29 degrees, with the trail extended to 5.3 inches (13%). Wheelbase jumped from 60.6 inches to 63.2—an increase of 2.6 inches, providing more room for rider and passenger. Honda was receiving the market’s signals. Air suspension was introduced, then in ‘82 came “Aspencade,” an all-sails-set tour package.

GL1200, the 3rd-gen, at last moved its torque peak down 500 revs, to 5000, but with 94 peak horsepower (up from the previous 81), and torque up from 65 lb.-ft. to 77.4. Engine revs at 60 mph had been 3700 rpm, but now dropped to a more comfortable 2977 rpm.

Chassis stiffness was increased—something we instinctively associate with sportbikes and racers. Yet all motorcycles are related. The more flexible the chassis, the less responsive the steering, as only part of the rider’s command reaches the front wheel, while the rest is lost as the parts between hands and tire flex. For Gold Wing, as for other kinds of motorcycles, increased chassis stiffness increased rider control and confidence.

Weight was climbing: 589 became 723—a 23% increase—as amenities like factory-installed luggage proliferated.

Increasing engine displacement increases the size of the thumps the engine feeds into the driveline, but even with flexible elements between engine and rear wheel, the thumping of larger cylinders became more noticeable, especially at low rpm, as when pulling away from rest.

In January 1984 a new team was assembled under Shigehisa Morinaka, and given the Gen 4 goals of combining greater smoothness and quiet with class-leading power.

Four cylinders became six, 300cc cylinders became 253 as displacement increased to 1520cc. With the displacement increase, the previous 94 hp at 7000 rpm became 100 hp at only 5200 rpm. Now the true nature of a touring engine was asserting itself, as peak torque rose to 110 lb.-ft. but down at 4000 rpm, a 1000 rpm drop. It was decided this 794-pound motorcycle needed an electric reverser to back it confidently away from a curb. The new engine continued with carburetors because the cost of fuel injection remained high.

Increased displacement is the most direct path to the desired power and torque (keeping up with weight and ever-faster traffic), consistent with low vibration. This is why modern tour bikes have an overdrive ratio, in which engine revs fall to a comfortable level.

In market studies, the Large Project Leader (LPL) for the Gen 5 Wing, Masanori Aoki, later revealed they had considered:

Aoki found that 90% of American riders liked the 1800cc six-cylinder prototype best, saying that “the GL1500 signs off too early.” This is a natural consequence of having to focus on bottom- and midrange torque. The result can be “wheezing out” at higher revs because the induction system has been optimized for the bottom. Engineers call this a “shed roof” torque curve, because torque is high at lower revs, but slopes downward as revs climb. More displacement!

The longer engine was fitted in by a combination of extended wheelbase and a fitted-to-engine-shape radiator.

The resulting Gen 5 would be produced for 17 years. Chassis became an extruded-spar twin aluminum beam structure with the engine as a structural member. The stiffer the chassis, the less help it needs from conservative (i.e., “slowed-down”) steering geometry, so rake stayed at 29 degrees while trail was reduced to 4.3 inches—not that different from current sport motorcycles.

The big new engine was given PGM fuel injection at last, a part of measures necessary to comply with emissions limits. Peak power rose to 117 hp at 5500 rpm, peak torque to 123 lb.-ft., still at 4000 revs.

Now brace yourself for the ultimate expression of touring engine design: the G6 Gold Wing of 2018 with four valves per cylinder. Traditionally, four-valve engines are associated with sportbikes, but they are also outstanding at combining low-end torque with plenty of top-end.

Here’s how: If we build two single-cylinder engines of the same bore and stroke, and we give one of them two valves and the other four, with total intake valve head area equal in both cases, valve perimeter (distance around the head) will be 41% greater in the four-valve than in the two-valve. As the valves begin to lift, this means the four-valve exposes 1.41 times as much flow area per millimeter of lift than can the two-valve. For equal intake flow, therefore, the four-valve can be given a shorter valve-open duration than the two-valve. The shorter the valve duration, the greater the bottom torque, because the intake valves need not be held open as long after BDC as does the single intake of a two-valve.

Delayed intake closing boosts top power, but at lower revs it allows some of the charge taken in to be pumped back out as the piston rises on compression. This reduces torque at lower revs. Giving the four-valve higher lift enables it to outflow the two-valve on top-end.

As a result, Honda claims 125 hp at 5500 rpm and 125 lb.-ft. peak torque at 4500 rpm.

Note that peak torque is given at higher rpm than in the two-valve model. Isn’t that going in the wrong direction?

A look at the actual torque curve for the G6 explains this; it is so nearly flat over a wide range that it’s difficult to see just where peak torque is located. It’s everywhere, as the G6 engine makes over 100 lb.-ft. all the way down to 850 rpm and all the way up to 4800. This is the special virtue of four-valve with short duration and light valve train components; it escapes from the classical torque curve shapes such as haystack, shed roof, Matterhorn, etc. I think of this as “table-top, or mesa torque.” When CW dynoed a G6 we found the rear-wheel peak torque at 1210 rpm. Rear wheel power was 98 hp at 5550

Finite Element Analysis (FEM) of major elements of the bike showed the way to a 90-pound weight reduction over the previous model. CW’s scale reported a wet weight of 833.

The G6 redesign also caught Gold Wing up with the electronic rider aids of the 21st century.

Another notable change was the abandonment of the previous telescopic fork for a kind of modern girder fork. Why? We know that with the longish flat-six engine it has been important to position it as far forward as possible so that the rider can comfortably reach the bars. Front wheel travel with a telescopic fork is up and back, moving toward the engine as front suspension compresses. But with a girder, wheel movement is mostly vertical, allowing an even more forward engine position. Getting the details right.

A dual-clutch seven-speed transmission was optioned (DCT) and 70% of buyers have been choosing it. Why the extra trans ratio? Five speeds plus highway overdrive left the bottom gears spaced far enough apart that the inertial thumps as an upshift pulls engine revs down were not consistent with Gold Wing’s character. The extra ratio smooths that.

Remember that DCT is not a “slushbox.” All the power is efficiently transmitted gear-to-gear just as in conventional gearboxes, and the traditional rise and fall of engine rpm as the bike accelerates through the gears is still there.

Gold Wing was something of a market experiment in 1976, but its riders have continued to guide its evolution in the direction of their needs. Onward.