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Suzuki GS 1000E
Surprising everyone, Suzuki Motor Company presented a late
prototype of GS1000, their first 1000 cc motorcycle in the Paris motorcycle
show, the 64th Salon an der Porte de Versailles, in autumn of 1977. I think the
final version of the bike was far more beautiful than the prototype. This photo
was published in the Finnish magazine Tekniikan Maailma 19/77.
The GS1000 was based around the successful GS750, which was
the lightest of the 750's available at the time. What Suzuki wanted was a simple
design, that benefited from solid engineering and light weight. And they
succeeded. The GS1000 was only slightly heavier than its smaller brother, which
was quite an achievement. By lengthening the stroke of the (relatively short
stroke) GS750 engine from 56,4 to 70 mm the cylinder displacement was enlarged
from 748 to 997 cc. The lower end of the GS750 was strong enough to cope with
the 1 1 liter cylinder displacement but the list of modifications was longer
than just adding 14,6 mm to the stroke. The redesigned 750 engine put into the
1000 was actually lighter than the 750 engine! The power output in 1978 was
given to 83—90 hp depending of the export country (differences in environment
and noise regulations).
CYCLE BUYERS GUIDE 1978
We first tested the GS on a race track in Japan. We ran 180 miles with a 101 mph average and came away with the opinion that the Suzuki is the best high-speed-handling multi available for sale. The primary component of the GS1000's high-speed accuracy is its chassis. Made of large-diameter, thin-wall STKM-13A mild steel, the frame weighs 38.3 lbs complete—only 1.55 pounds more than that of the 750. While it resembles the 750 chassis in that it houses a four-cylinder engine and is painted black, in all specific respects it is completely different. Tapered roller bearings are used to support the steering-head axle, caged needles live in the swing-arm pivot area, and the tubular swing arm itself is the largest one fitted to any current big bike (42.7mm in diameter, compared to the GS750's 38.1 mm dimension or the Kawasaki KZ1000's 41.2mm). The 1000's swing arm is also 30mm longer than the GS750's.
But the search for stability explanations must begin under the fuel tank. The way the chassis is braced is remarkable. Complex pressed-steel gusseting extends from just below the top of the steering-head part way down the front down-tubes, ties in with a tubular crossmember steadying the side rails and terminates in a large, scalloped, pressed steel brace. The T-shaped backbone sprouts tubular members connecting it to the side rails, which are tied together no fewer than five times between the steering head and the seat.
Suzuki recognizes that enormous forces act on, and try to deflect, the steering head; the bracing and strengthening serve as evidence. That it all works is demonstrated by the bike's willingness to remain stable when the front brake is applied with the bike leaned over entering a corner. The combination of forces generated by these two simultaneous activities—braking and turning—has consistently rattled Japanese multis and generally results in a low-frequency, wide-amplitude wallow that's different in nature and more difficult to control than the more ordinary wallow created by inadequate shock absorber rebound damping. We do not pretend to understand all the dynamics of this particular mode of instability, but we suspect that steering-head flex is a primary cause.
We also suspect that fork-pipe flex is a secondary cause. Obviously Suzuki suspects the same thing because the GS1000 is fitted with larger-diameter fork tubes than anything from Japan except the Honda GL1000. The GL and the GS share 37mm fork pipes. The Yamaha 750 triple, Kawasaki KZ1000 and almost everything else use 36mm tubes.
So the bike has a solid swing arm, solid fork pipes, solid steering head support and a solid, lightweight chassis. That's half the battle. Suspension components are the other half, and here too Suzuki has gone far beyond convention and into the technological future. The GS1000 has an air-adjustable fork (dual-rate coil springs remain) and adjustable-damper rear shock absorbers—both street bike firsts. These suspension components-working with the bike's ultra-stiff chassis and swing arm—form the bridge joining handling stability with riding comfort.
Air forks have been around for several years now, either as OEM equipment on standard motocrossers or in the form of kits supplied by the aftermarket industry, But the GS1000 is the first standard production street bike to come so equipped, and the air fork works astonishingly well.
Air is a wondrous spring material. It is infinitely adjustable and infinitely progressive; its drawback in most motorcycle suspension applications is its eagerness to escape. That's why the Suzuki retains its conventional steel fork springs, and why the Suzuki engineers have used air only as a secondary spring medium. In the GS1000, air provides an easy way to fine-tune the fork performance.
The sophistication on the front of the GS1000 is matched in the rear. The bike comes with the first adjustable dampers ever fitted to a street motorcycle, and they are, if anything, even more effective than deed produced a breakthrough: the GS1000 is the first multi-cylinder motorcycle we have ever tested which feels completely comfortable at high-speed.
If we had any critical comment to offer about the GS's high-speed handling character, it would be in the area of cornering clearance. Only the Honda CBX, among the current crop of maxi-multis, has more—and it has a lot more. The GS dragged its header pipes, footpeg ends, header pipe clamp rings and assorted stand paraphernalia.
All this chassis and suspension detailing wasn't wasted by fitting the bike with a the air-adjustable front fork. Like the fork, the shocks are manufactured for Suzuki by Kayaba, and will be supplied to Suzuki exclusively for at least a year.
Beneath a contoured rubber boot above each shock's upper spring collar is a serrated wheel with numbers 1 through 4 stamped around the edge. There are slots machined adjacent to each number, just large enough to accommodate the end of the bike's ignition key. The wheel is attached to the top of a rotary rod within the shock's main piston rod. Turning the wheel turns the rod, which causes different-sized holes to align with a larger hole in the damper rod. Put simply, if #4 provides 100 percent damping force, then 3 yields 86 percent, # 2, 72 percent and 1, 57 percent. The dampers are adjustable in more than name only: the total range between softest and firmest is 43 percent.
With this kind of available damper performance spread, the GS owner will have to be careful to correlate damper setting with spring preload. On the Ryuyo test track we started with maximum spring preload and #2 damping position, and progressed up to #4. The improvement in high-speed stability was incredible, particularly when the dampers were dialed from #2 to #3. When we clicked up to #4 we recognized that Suzuki had indog of an engine, either. Running into a strong headwind down Ryuyo's main straight, the bike registered a top speed just the width of its own needle below 140 mph. It may look like a GS750 engine; it most assuredly does not act like a GS750 engine. It shares the 750's 26mm carburetors and miscellaneous decals and covers, but inside, it's its own engine.
For starters it has a completely different crankshaft. The 750 has a full-circle-counterweight crank; the 1000 (997cc actually) has a crank of the pork-chop persuasion, which is more than two pounds lighter than the 750's despite its 8.4mm increase in stroke. The 750's primary gearset is straight-cut; the 1000's is helical. Rods and pistons are generally the same except in dimension: the 1000's rods are almost 2.0mm shorter, and its pistons are 5.0mm bigger. The big GS also uses 2.0mm larger piston pins and a cylinder which is 3.5mm longer between the gasket surfaces.
Upstairs there are many differences. The 1000 uses a racing-type (square-plate) cam chain, no between-cams idler sprocket, the same valve angle (30.5 degrees from bore centerline) but different-sized valves (38mm inlet and 32mm exhaust compared to the 750's 36mm inlet and 30mm exhaust), and 9.2:1 compression as opposed to the 750's 8.7:1. Both engines share Suzuki's self-adjusting cam chain tensioner.
None of this is beyond-the-mainstream engineering—except for one thing: the GS1000 engine is lighter than the GS750 engine by exactly ten pounds: 199.5 pounds vs. 209.5 pounds (with carbs).
No major manufacturer builds motorcycles in a vacuum. It's almost certain that Suzuki has been aware for more than a year of the activities of Honda, Yamaha and Kawasaki in the Superbike field, and consciously pursued handling, low weight and simplicity as a strategy by which the GS1000 could stand apart from the XS Eleven, Z1-R and CBX. The GS1000 is lighter. It does handle better. And it is simpler. It is also, the Eleven aside, much more comfortable, despite a handlebar bend which aggravated two of our test riders' backs and a seat which is not up to the level of the Yamaha's. It is also fast, and fast in a useful way. In high-gear roll-ons against the King of the Mid-range Blast, the Eleven, the GS lost by a couple of bike-lengths. But against the Honda Six it marched into the middle distance, leaving the CBX wondering what happened.
On the open road, displaying its touring and comfort face instead of its go-get-'em racer face, the GS is a real treat. Engine vibration is about the same as the GS750's, the suspension suppleness provides a constant source of delight, and all the instant power you could ever need is there if you have to pass quickly.
Although we had some minor difficulties with our test bike (a periodic unwillingness to idle, for example), we believe that the biggest GS is the most complete motorcycle in this brand-new four-bike field. It handles better than all of them (although its margin of superiority over the CBX is a small one), weighs less, and costs less (at $2749, it's $240 cheaper than the XS Eleven, and almost $1000 under the Z1-R and the estimated price of the CBX).
But where the Suzuki breaks most clearly with current Superbike convention has to do with where the emphasis is. On the Honda, Yamaha and Kawasaki, powerplant engineering is the message. While the Suzuki four-cylinder's acceleration and top speed capabilities are more than competitive in this scalding-hot and muscle-heavy class, the engineering behind its chassis and suspension components, together with its light weight, are the main focal points. Suzuki is gambling that the American market is mature enough to connect with this higher order of performance, balance, and completeness. We think it's a good gamble; we know it's a stupendous motorcycle.
Source CYCLE BUYERS GUIDE 1978