Suzuki GT 250

Road Test 1975

Consider for a moment a heretical proposition: Suzuki builds two-strokes for road-going riders who don't particularly like two-strokes. Think of two-stroke roadsters and what do you picture? In the case of 250cc twins, you imagine something raspy, noisy, pipey, intense, snappish and quick. You expect a machine that reacts reflexively rather than responds deliberately—at least when new. And when well used up, there's nothing quite so loose and pathetic as a high-performance two-stroke which has lost its sting and can only raise a baleful induction boorrrkkkk.

High-intensity two-strokes—front-line hardware like the Yamaha RD 350—are built for people who love two-strokes. Suzuki's GT 250M is different. Suzuki has strained out all that two-stroke temperament; finely processed and packaged, the GT 250 is the most "four-stroke" small-displacement two-stroke anywhere. It's more akin to Honda's CB-360 than Yamaha's RD 250. Far from being a snarling cat, the Suzuki 250 is a mellow pussycat, so well-coached that you needn't be a certified two-stroke lover to buy one.

Suzuki has subtracted much of the 250's two-stroke nature, and many riders will bid those things good riddance. For starters, the ping-ding piston clatter has been throttled. The GT 250M has conservative three-port cylinders and relatively simple pistons. So there are no short, perforated pistons rattling around inside cylinder bores which have been slotted, chopped and channelled. Such power-carving eventually results in slightly collapsed pistons that bang around in the bores and produce that Yamaha-Kawasaki cylinder/cymbal serenade. Suzuki's longish pistons and straightforward three-port design leaves a great deal of piston-to-wall bearing surface which helps hold down piston-slapping noises.

Concern for quiet—and the suppression of piston clatter—extends to the exterior of the engine. Suzuki's RAS (Ram Air System) includes a two-piece cast-aluminum hood which fits over the cylinder heads. The rubber-mounted shroud, according to Suzuki, keeps the engine running at "optimum operating temperature." Fair enough, but you'll neither seize the engine nor notice a drop in performance nor knock down the gas mileage by removing the shroud. You will, however, elevate the noise level.

Using the California standard for measurement, the sound level increased one decibel (average) over the stock 84.5 figure. Only a sharp ear could detect the difference, but the sound meter registered the gain. From the saddle you don't need a meter to ascertain the difference the shroud makes. Starting the engine from dead cold produced the customary air-cooled two-stroke sounds; before the engine reached its normal operating temperature and the running clearances closed down, it was rattle-city without the shroud. Once warm, the Suzuki became quieter, but it remained remarkably noisier sans ducting.

Very effective intake plumbing filters down the intake honking. Indeed, Suzuki has so successfully squelched engine and intake noises that the overriding sound comes from the exhausts: a curiously flat sputtering, almost motorboat in character. The sound doesn't incorporate that whoofing whine of many two-stroke twins. Nor is the hard exhaust note a particularly attractive sound. Perhaps that's why the exhaust seemed louder by ear than it proved to be by meter-measurement.

Things beyond silence recommend the GT 250M. Fifteen-cubic-inch motorcycles are physically large enough to provide sufficient space for reasonable comfort even if you're six-two and pressing two-hundred pounds. For big riders no 250 will work as well as a 500 or 750, but the GT 250M has as much room as any sub-400. Basic space relationships between the seat, bars and footpegs at least won't cramp fuller-sized riders. Those five-nine and under may find the 31-inch saddle height (laden) troublesome at stoplights where they must balance on tiptoe. Some smaller riders might try to flat-foot, using one leg as a prop. This technique will quickly reveal that lightness is a lost virtue in the 250cc roadster class.

At 353.5 pounds (wet), no one could call the GT 250M a lean machine. It is a good 50 pounds heavier than small-displacement street bikes, but 30 pounds lighter than most 350-400cc machines. The Honda CB-360T weighs in at 384 pounds and the CB-400 tops 400 pounds. On the other hand, Yamaha's RD 350B weighs a pound less than the Suzuki.

Much of the GT 250M's weight has been invested in those convenience features which make motorcycling a relatively civilized sport for street riders: full instrumentation, oil injection, appropriate idiot lights, as well as federally-mandated equipment. The only convenience which has escaped is electric starting.

Suzuki's 250 has been well-schooled in the art of rendering no offense. Kick-starting is the biggest effort a rider need make with the bike. He has no obligation to turn on the fuel-line petcocks since the vacuum-controlled diaphragms in the taps open the lines as the engine starts. The rider can even skip the formality of returning to neutral before stabbing the lever; with primary kick-starting, he can simply pull the clutch in and proceed. The rider must remember only to turn on the ignition… and kick.

The only truculence displayed by the Suzuki 250 was hesitant cold-morning starting (in near-freezing temperatures). After depressing the left-side choke lever, four-to-seven energetic kicks would coax the engine to fire up. There followed a mile of staggered running during which the engine would die at traffic lights with the choke on, or off, or any position between stations. Once warm, the bike immediately settled into its well-behaved form; reliable idling returned and one-nudge starting became the rule.

The clutch and brake levers demand little hand pressure to get results. The clutch lever has a sufficiently wide engagement arc, and that hedges against those novice stoplight launches which commence at a full-gallop lurch. Riders with small hands may not be able to get a closed-hand grip on the brake lever before its draw begins to stiffen, though you can apply enough pressure with a stretched-out hand to yank down the speed in a hurry. Unfortunately, Suzuki hand levers have fairly small cross-sections, and they can feel like blunted blades if you're accustomed to wider levers. Gloves lessen the blade effect.

Rough-rider types, in fits of iron-willed stupidity, will probably dispense with the clutch for three/four/five/six upshifts. This mischief won't trash the gearbox for two reasons. First, the gears are quite hefty since the 250 originally shared its transmission with Suzuki's hard-running 315cc twin. Second, the 1975 Suzuki 250 doesn't make enough power to hurt its transmission or anything else. Had Suzuki been playing the horsepower-race game, the 1975 250 might have made more power than the first 1969/70 315cc twins, and a really strong 250 might have threatened the transmission. Suzuki, however, has steadily backed down the horsepower from year to year, relying on the six-speed transmission to make the most of what is available.

Rowing through the gears to the 8000-rpm redline forces the engine to reveal itself as a two-stroke twin. Above 5000 rpm the engine radiates that familiar high-frequency, low-amplitude vibration. The bars buzz, the footpegs ring in harmony, and the saddle joins in too. Nothing too serious, of course, and the situation stays tolerable. Nevertheless, since the engine works so well in the sub-5000-rpm range, most riders will stay out of the upper-rpm band. The GT 250M has mellow down-under power, and the bike falls into its most pleasant gait with 5000 rpm showing on the rev-counter. The Suzuki twin pulls slightly taller sixth-speed gearing than Yamaha's RD 250 (11.4 mph per 1000 rpm vs. 10); this gearing helps subdue engine vibration and permits the Suzuki twin to work at a more leisurely pace. The Suzuki engine feels as if it could go on forever at 5000 rpm, where it spins with amazing smoothness. Even the image in the rear-view mirror remains unblurred.

The front suspension, which became more supple as test miles accumulated, proved a better match for freeway irregularities than the stiff rear units. Spring harshness combined with the GT 250M's short wheelbase to produce a choppy ride, especially over the slab sections of any concrete roadway. The stiff rear suspension keeps the bike taut enough on winding mountain roads, but thrashing through a bump-mined corner would cause the rear end to skitter and skate out. A ground clearance problem exists on the left—the side stand grounds out. On the right, there's no such hinderance and attendent danger.

Response to steering inputs is slower than the Yamaha RD 250. Suzuki has biased the steering geometry to produce a feeling of great stability straight-up and heeled over. Furthermore, the GT 250 has lost horsepower over the last few model years though the running gear has been unchanged. The diminished power makes the bike feel as if it responds more deliberately to steering inputs than before.

If you find a smooth asphalt road, click the Suzuki into sixth, and put on your touring hat, you can motor on in comfort for 200 miles. After that, the firm saddle begins to wear on your buttocks. The GT 250M has an honest-to-touring range; you can go 140 to 150 miles before the engine starves out on its main fuel supply. Cheers for the four-gallon tank; someone at Suzuki realizes that people actually ride motorcycles where gas stations are more than a couple of blocks apart.

Suzuki's instruments must have been built at a liar's convention. At first gas mileage seemed a phenomenal 50 mpg. Wrong. Careful investigation turned up a deceitful odometer which tossed in an extra six-tenths every ten miles. Recalculated gas mileage figures fell accordingly. The odometer fudging seemed small compared to the tales the speedometer concocted. Unforgivably off, the speedometer recorded 60 mph although true speed was only 51 mph. The large error is doubly annoying because most riders hover at the 55-mph limit and many police start writing tickets at 56-58 mph. No one should be left guessing about his actual speed, wondering if an indicated 66 mph is really 53 or 55 or 58.

The GT 250M's power grows along a gently inclined plane; there's not a Yamaha-like surge anywhere in the powerband. Not only has the 250's power curve been ironed out, it's also been driven down. During Cycle's last encounter with the GT 250 (February 1973) staffers discovered that Suzuki had an effective (but crude) way of limiting sound output: at "full throttle" the carb slides still hung down six millimeters in the carburetor bores. The six-millimeter difference created a presto sound (and power) governor. You'll be happy to learn that Suzuki has long since abandoned that rude and unseemly trick; alas, more sophisticated means have been found to squeeze down the power.

The 1973 bike produced 22.32 horsepower at 7500 rpm, exactly the point of maximum torque too, 15.63 pounds-feet. The 1975 version still makes maximum power at 7500 rpm, though the peak has been shaved to 20.14, for a loss of ten per cent in three years. The torque curve reaches only 14.88 pounds-feet at 7000 rpm. Generally the 1975 horsepower curve looks very much like the 1972 chart, though the curves show the most divergence after 5500 rpm. From 6000 rpm upward, the 1975 version is never more than 95 per cent as strong as the earlier model.

Once again quarter-mile dragstrip times verify this taper-down effect. The 1972 Suzuki 250 clocked the quarter at 16.24 seconds, hitting the traps at 79 mph. "Progress" has pulled the time back to 16.53 seconds and driven the speed down to 77.05 mph.

There is still good news of sorts. There are points (3000 rpm and 5000 rpm) at which there's been no loss at all or a slight gain. The 5000-rpm slot is especially crucial since that corresponds to the cruising speed in sixth gear on the open highway. In a high-gear-only pass (using 5000 to 5500 rpm) there would be no difference between 1972 and 1975 Suzuki 250s.

Building a twenty-horsepower two-stroke twin doesn't involve a lot of trickery—booster ports, reed valves and snakey passages can all be avoided. Very basic porting suffices in the Suzuki (intake, exhaust and two transfers). Generally three-port design is adequate assuming the manufacturer is dealing with small cylinder sizes and not looking for a lot of power. Blazing power doesn't interest Suzuki; but tractability, economy, simplicity and silence do. The intake timing is fairly short duration and the transfers direct their charge sharply back across the pistons; these features lead to those power characteristics which Suzuki wanted in its 250 twin.

There's a final advantage to the three-port design. Compared to more complex cylinder layouts, it's inexpensive to produce. By today's standards, the $995 GT 250M begins to sound like a bargain—a tribute to the economy of continued development.

With the 500cc Titan twin, the 250 roadster is the longest surviving bike in Suzuki's street line-up. True, the bodywork has changed, RAS debuted in 1973 and other refinements have been added. Yet the current 250 Suzuki twin has had a long six-year production life in its fundamental configuration. Certainly the GT 250M isn't "all-new," but the world probably isn't waiting breathlessly for a pricey all-new 250 roadster.

The GT 250M is a lot of things: solid, unexciting, inoffensive, dependable, bland and idiot-proof. Those qualities also describe the Honda CB-360T, CB-500T and Kawasaki's KZ-400. These bikes all lack strong characters and suffer identity crises. Why? Because engines really define most motorcycles, and without exception charismatic bikes have engines which excite enthusiasts. But motorcycles like the GT 250M don't have those sorts of engines. They have power modules which could just as well be black boxes that turn gears with an intricate system of rubber bands. Traditionally the best black-box power units have been four-strokes. Suzuki has demonstrated that two-strokes can serve just as well.

Source Cycle Guide 1975