Retrospective: Suzuki GS750E/ES: 1983
The alphanumeric system that defines many Japanese motorcycles has never been very instructive, and the bike we are writing about here was only a one-year model…but it was a good one. Suzuki was the last of the Big Four to get into the four-stroke game.
Seeing the EPA’s handwriting on the engineering wall, the Hamamatsu-based company came out with its first UJMs (four-stroke, in-line 4-cylinders) in 1977, in both 550 and 750 sizes. The engineers liked the oversquare design as it allowed for higher rpm, and the GS750 (748cc) had a 65mm bore, 56.4mm stroke, using two overhead camshafts and two valves per cylinder, and put out an estimated 60 horses at the rear wheel. While most of the thought had gone into the engine, the chassis shop had created a passable cradle frame, making it comfortable for the average rider but stiff enough to keep the go-faster happy.
The GS750 sold extremely well, but the engineers kept on working and, as the ’70s came to a close, Suzuki R&D was completing the 1980 version of the GS750, now defined by the addition of an E. And 16 valves.
Suzuki engineers used increasingly oversquare cylinders, with a wider 67mm bore and short 53mm stroke for the 747cc motor, topped off by something called the Twin Swirl Combustion Chamber (U.S. patent #3533577, for anyone caring to know more). This was back when the Japanese loved hanging a lot of initials on their technology. The TSCC used a flat piston and four rather small valves, with a narrow 40-degree angle between them. This narrow angle allowed for a flatter head, with the centrally located spark plug closer to the combustibles in the shallow chamber. Better bang, better power. The top of the piston was indented in four places to accommodate the valves.
Valve adjustment was almost old-fashioned, with locknuts allowing home mechanics to get the gaps right…or wrong, depending on their competence. Fuel was delivered via four 32mm constant-velocity Mikuni carburetors, and compressed at a rate of 9.4:1. Maximum power, 65 horses, came on at 9,000 rpm, with good torque—40 lb-ft, from six to eight thousand—you couldn’t really ask more of a 750 back in 1980. Straight-cut gears passed power through a wet clutch to a 5-speed transmission, then out to the back via a 630 chain.
Sportbikers were mad for these new 750s, and dealers were putting them out the front door as fast as they came in the back. Suzuki appreciated that few of these GS750E models would ever see the inside of a race course, and the key was to make the chassis suitable for the street rider, who was not appreciative of too much stiffness and liked to feel the bike respond quickly to the steering inputs. The frame was a double-loop full-cradle, with the suspension opting for
comfort over cornering.
Rake was 28 degrees, with a trail of 4.1 inches. Riding like you stole it, bits and pieces like the centerstand and footpegs might scrape in corners, but just take off the stand as any serious roadracer would do. In 1981, this model did get air adjustability on the leading-axle fork, and the shocks got rebound-damping adjustability, along with standard preload. Cast wheels carried tubeless tires, a front 19-incher, the rear, 18. Braking was done by three slotted 11-inch discs, each using a single-piston caliper. The art of serious braking efficiency was just beginning to come out of the Dark Ages.
All this was in a wheelbase of barely over 60 inches, and a curb weight of 540 pounds—which included the five gallons of gas in the tank. A competent drag racer in the saddle could turn a quarter-mile in under 13 seconds, with a speed of more than 100 mph. As an around-town bike, the GS750E excelled, with plenty of power in the lower rpm range. And on the highway, it was smooth and fast.
Then for 1983, the last iteration of the E received major changes, from sheet metal to chassis. About the only thing unchanged was the bore and stroke of the engine, and the size of the Mikuni carbs. A lighter crankshaft had been fitted, slightly bigger valves, and a small increase in compression ratio to 9.6:1, with the power now over 70 horses at 9,500 rpm. Everything that could be lightened was, from transmission gears to fins, and the result was an engine/tranny that weighed, according to Suzuki, 28.7 pounds less than its predecessor and was physically
That last part was essential because Suzuki was going modern with a Full Floater single-shock rear suspension, which intruded on the engine space. A new frame connected the swingarm and new 17-inch rear wheel to the steering head, and the front fork was now a bigger 37mm item, sporting that anti-dive valving. At the bottom of the fork, the 19-inch wheel was tossed and replaced by a 16—drastic! The idea was that the 16-incher, followed by a shorter wheelbase, could handle as quickly as a 550. This was where the sporting world was going at the time—though a few years later the sportbikes were all running 17-inch fronts. Everything was tucked into a wheelbase more than an inch shorter than before at 58.9 inches, with a slightly steeper rake (27.8 degrees) and the same trail.
The styling was all new, with two models being offered. The GS750E now had a frame-mounted bikini fairing, and the ES came with a half fairing. The seat had a racy rear end, and the exhaust system was all black. The ES in the photos has aftermarket lowers on the half-fairing and a four-into-one Supertrapp exhaust.
The riding position was new, too—while the previous GS750E had been considered primarily an urban machine, the new low, two-piece handlebar and slightly rearset pegs definitely had the rider in a semi-racy crouch. American riders were just getting into the notion of serious sportbikes, and this was a great success, worthy competition for Honda’s Interceptor.
Then the Reagan Recession descended on us, resulting in many unsold units, meaning none were imported for 1984. This was followed by the tariff-induced GS700E/ES in 1985. And then—hang the taxes—along came the all-new GSX-R750 in 1986.
(This Retrospective article was published in the August 2013 issue of Rider magazine.)