The Yamaha YX600S Radian

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1986 Yamaha YX600S Radian
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1986 Honda CB700SC Nighthawk
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1986 Kawasaki ZL600 Eliminator

Years produced: 1986-1990 
Claimed power: 66hp @ 9,500rpm (56hp @ 9,500rpm/period test)
Top speed: 125mph (period test)
Engine type: 598cc DOHC, air-cooled inline four
Transmission: 6-speed/chain final drive
Weight: 436lb (wet)
Price then: $2,399 (1986)
Price now: $750-$1,850
MPG: 45-55

The mid-1980s were challenging times for the motorcycle industry. After years of double-digit growth, motorcycle manufacturers everywhere found themselves fighting a steep slide in sales, with little hope of a quick rebound. Faced with a changing and constricting market, Yamaha, like every company, took a long look at its products and considered how it should adapt to a new reality. Shedding the bikes that had carried it into the 1980s, the Hamamatsu-based company redefined its image with a new range of machines including the V-twin Viragos, the Maxim series, the Vision and the FJ series. In 1985, Yamaha hit two major home runs when it introduced the 5-valve FZ750 sport bike and the V-Max, a liquid-cooled, 1,200cc V-4 adrenalin rush that quickly became the new king of the strip and the street.

The new standard
It was in this environment that Yamaha rolled out the apparently all new (more on that in a moment) YX600 Radian for 1986. Although hailed as a new standard, stylistically it was sort of a Mini-Me to Mr. Max, with Max-like touches including chromed tops on its CV carbs, chromed plastic “velocity stacks,” chromed instrument pods, and 7-piece plastic bodywork (excepting the metal gas tank) clipped to a relatively low-slung chassis. Power came from an air-cooled, 598cc inline four exhausting through a stubby, chromed 4-into-2 exhaust system. A 6-speed transmission took care of shifting duties, while a chain delivered the Radian’s claimed 66hp to the rear wheel.

So what made it an “apparently” all new motorcycle? In as much as the Radian was a new model and something of a new look for Yamaha, there was very little on the YX that hadn’t already seen service on another Yamaha. For all its newness, the Radian was a parts room special, created by raiding the corporate parts bin and deftly combining bits and pieces until Yamaha’s engineers and stylists ended up with their desired result.

Using existing parts to create something new was hardly a fresh concept; manufacturers have been doing it forever, and still do. For one, it’s economical, enabling a manufacturer to use proven and — more importantly — paid for pieces. For another, it cuts development time enormously, since most of the bike already exists, its parts just waiting to get reassigned to a new whole.

In the Radian’s case, the engine was the tried and true 8-valve inline four used in the FJ600, but modified with 2mm smaller carburetors (30mm instead of 32mm) and other tweaks for better mid-range and low-end torque. The carburetor airbox was lifted from the 550 Maxim, as was the frame, which made sense as the FJ600 engine case was the same as the 550 Maxim, making the FJ600 mill a bolt-in proposition. Further, the aluminum grab rail on the seat tail was from the Fazer, as were the Radian’s tach and speedometer, headlight, taillight, mirrors and turn signals. The front disc brake rotors were from the RZ350 and the calipers from the FJ600, while the shifter was from the 550 Maxim. Outside of its bodywork, the only parts unique to the Radian were the front forks and rear shocks.

Bang for the buckTesters couldn’t say enough good things about the Radian, and certainly its low $2,399 price tag went a long way toward explaining why. “This is a machine that would be a solid buy at around three grand,” Cycle World enthused. “But at $2,399 it’s a screaming deal. It has to be the best buy of the year.”

Further impressing testers was the feeling that the Radian was a machine whose whole seemed more than the sum of its parts. Road Rider called it “the Most-Fun-For-The-Dollar” motorcycle bargain of the year, lauding it as a more “superior all-around motorcycle than any of the narrowly specialized craft from which it borrowed its various components.” Underscoring that point was the Radian’s excellent performance, the new bike coming in two-tenths of a second and 3.5mph faster in the quarter mile than Yamaha’s own sporty and non-derivative FJ600.

No machine is ever perfect, of course, and the Radian was singled out for a few faults. Chief among them, ironically enough, was its poor suspension performance. Seems those few parts unique to the Radian weren’t fully developed, as testers universally complained of springy front forks and weak rear shocks with insufficient damping. The Radian’s riding position was also a source of irritation, not because it was too sporty or too upright, but because the bike’s short wheelbase and tight packaging squeezed riders much taller than 5 foot 10 inches.

But those niggling complaints didn’t get in the way of the Radian being declared Cycle Guide’s Bike of the Year for 1986, and a Best Buy by just about every other publication.

Given the Radian’s parts bin makeup, its no surprise Yamaha changed very little on the bike from 1986 until it was pulled from the lineup after the 1990 model year. In fact, about the only change of note came in 1989, when Yamaha inexplicably relocated the Radian’s alternator from behind the cylinder bank to the left end of the crankshaft, leaving it vulnerable to damage in the event of a left side touchdown.

While some might question the “classic” merit of the Radian, there’s no denying its role in Yamaha’s success. Good looking, well mannered, more than fast enough and remarkably cheap, the Radian is still one of the best buys from the 1980s. MC

Four-cylinder rivals to Yamaha’s Radian
1986 Kawasaki ZL600 Eliminator

– 73hp @ 10,500rpm (claimed)/ 107mph
– Liquid-cooled, 592cc DOHC 16-valve  inline four
– 6-speed
– Disc front, drum rear
– 468lb (wet)
– 40-45mpg

Introduced the same year as the Radian, the ZL600 was Kawasaki’s new standard. Not a cruiser, although it leaned heavily that direction, and certainly not a sport bike, it was, however, a better performer than either its looks or lineage would suggest.

Styling came straight from its big brother, the ZL900 Eliminator introduced in 1985. Like the ZL900, the ZL600 had a drag strip/bad boy look, with a heavily stepped seat, slash-cut shorty mufflers, black engine cases with chromed side covers, and wide, tall handlebars with a lazy pullback for cruising with some ‘tude.

Powering the ZL600 was the liquid-cooled, 592cc inline four introduced on the Z600 Ninja the year before, although with shaft final drive instead of the Ninja’s chain. But importantly, while the ZL lost 5hp to the Ninja overall, it was actually faster 0-60mph (3.36 seconds versus 3.52) and produced more horsepower at mid-range roll-on, the zone where most people really use power. Like the Radian, the answer was in smaller carbs (30mm versus the Ninja’s 32mm), which greatly improved the engine’s low- and mid-range response. The Ninja could best the ZL in final top speed, but at anything less the ZL would actually leave the Ninja in the dust.

Not yet — and maybe never — a classic, the ZL600 is an interesting reminder of mid-1980s style and performance.

1986 Honda CB700SC Nighthawk– 67hp @ 9,500rpm/125mph (est.)
– Air-cooled, 696cc DOHC 16-valve inline four
– 5-speed
– Twin-disc front, drum rear
– 516lb (wet)
– 40-45mpg

Just as Yamaha was bowing in with its “new” standard-style Radian, Honda was about to pull the plug on its own hot rod standard, the 696cc Nighthawk S.

Introduced in 1984, the 700 Nighthawk was an odd recipe of one part old-school to two parts new. While the Nighthawk’s twin-cam, 16-valve engine was all new, its air cooling was not, making the new Honda mill something of a throwback. Even so, it featured new-school amenities like hydraulic lifters (making valve adjustments a thing of the past), a no-maintenance driveshaft, electronic ignition, an automatic adjuster for the cam chain and a spin-on, automotive-style oil filter.

The Nighthawk’s inline four displaced 696cc to the Radian’s 598cc, and produced an honest, dyno-tested 67hp as opposed to the Radian’s “claimed” 66hp (Cycle’s dyno pegged the Radian at closer to 56hp). But the fact it was carrying an extra 80 pounds over the Radian erased any potential top end advantage. Like the Radian, many testers saw it as a new take on an old routine, the standard. An all around excellent motorcycle, it was also $1,500 pricier than the Radian, making it little surprise Honda didn’t extend its life cycle any farther once the Radian hit
the market.

Motorcycle Classics Magazine
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