Suzuki GT 380J

Road Test 1972

Visually, the 380 mostly makes it as a Gran Tourismo. It's big and massive and heavy looking, dense and compact. Following the GT design theme, the 750, 550, and 380 are all very similar in component shape, instrument/control layout, and finish. If pictures of the three were compared, with the engine areas blanked out, you would have a hard time figuring out which bike was which. The colors and tank panel designs and badges differ, and one has a radiator, but that's about it.

The fuel tank adds a lot to the bulky, squat look of the 380. Its squarish corners and barrel-chested depth complete the illusion.

Even the white accent splash is created to give a blunt-headed massive frontal attack effect, the Suzuki badges on both sides of the tank are separate metal castings that look somewhat nicer than the decal or painted-on type. A wide, deep center saddle in the tank saves the bulk for illusion: fuel capacity is a moderate four gallons. The tank's saddle space is occupied by three ignition coils and the very Norton Manx-looking frame-tubing pyramid. A very nice flip-up filler cap has a key lock on its release button. Suzuki says that they have traced a lot of their warranty problems to tank additions by owners' enemies. The cap seals absolutely perfectly.

Other painted pieces are the headlight shell, the upper fork covers, and the side panels. The side panels don't do all that much for the gut-level visual reaction to our machine. Phony air vents molded into the ABS plastic and pointy-toed corners make the covers look extremely forced. The two colors available are Jamaica Red and Hawaii Green. The frame is black. A tasteful use of bright polished surfaces balances the black and colored paint.

One of the first things that strikes your eye on the 380 is the cast aluminum shroud that is fastened to the tops of the cylinder heads. The shroud lifts to form a high scoop over the center head. When Kawasaki introduced their three, overheating problems were encountered by owners who changed the front fender or added an accessory in a place that partially blocked air flow to the cylinders. The problem became critical only when the atmospheric temperature was very high, but torque was reduced substantially in the non-critical zones. Last fall, Suzuki experimented with air-directing shrouds on their road racers at the Ontario AMA National. By using the shrouds, they were able to use higher compression ratios without suffering from overheating. Carefully instrumented tests showed that like increases in torque were to be had from the 380 at high cruising speeds on the highway. Vibration noise, mechanical fatigue, and expansion rate problems are all alleviated by using silicon rubber grommets between the one-piece shroud and the three individual cylinder heads. The tops of the sparkplug caps are sealed, like those on a VW, where they pass through the shroud. Contrary to the advertising term used by U.S. Suzuki for the shrouding (Ram Air Induction), the system has no direct effect on the carburetion or cylinder inlet systems.

As on the GT-750, the center exhaust pipe splits to feed two mufflers that are smaller than the single systems on the sides. The reason for this split seems to be more for looks than anything else. Four look better than three. The exhaust systems are beautiful, sweeping gracefully from the cylinders and tapering gently into the mufflers. At the ends of the mufflers, they taper back sharply to form a reverse cone.

Inside, the engine is put together in a very straightforward way: none of the spatial trickery of the GT-750 is employed. In fact, the 380 engine is very similar to the Kawasaki threes internally. The 380 is virtually an X-6 Hustler engine with another cylinder grafted to the left side. The bore and stroke are the same, and cylinder layout is identical except for minor porting differences.

Primary drive is via a helical gear on the right end of the crankshaft, which mates with a gear on the back side of a wet clutch. The clutch turns the mainshaft, the drive sprocket is on the end of the layshaft, and in between is a six-speed gearbox almost identical to that of the X-6.

A lot of two-strokes have the breaker-points on the end of the crankshaft. Many of them suffer from ignition timing variances when the engine gets hot and the mainbearing clearances increase. The 380 avoids that trouble by having a separate breaker assembly drive that is nylon-geared to the right end of the crankshaft. The assembly has its own double ball bearing support, which results in consistent ignition timing and a resulting consistency in engine performance.

The alternator is driven directly on the left end of the crankshaft.

Starting our GT-380 was always a one-kick operation. The fuel valve is a diaphragm-type automatic metering affair that does not require closing each time you park the bike: the diaphragm is operated by pulses from the inlet manifold, and no fuel flows unless the engine is running. Pulling a small lever on the left hand grip enriches the carburetor metering for cold engine starts. A flick of the ignition key, perched up between the speedometer and tach, allows primary current to flow into whichever coil happens to have its points closed. There's an emergency thumb-operated ignition switch on the throttle assembly, so you must see that it is in its on position. Then, one jab on the kicks-tart lever pedal does it every time.

Soon, the three settles into a familiar, but deeper-throated, bum-bumidy-bum-bum two-stroke idle. Ah, that seat is nice. At a mere 31-inches off the ground, it would allow our six-footer to sit flat-footed. Things even out in the engine after about three minutes. A six-pound pull on the clutch lever (easy) and a push down on the left foot pedal lets the little green light in the tach go out, and you know you're in first gear. You wouldn't know otherwise, for there's no clunk or clash to tell you. The engine stutters a little and you have to slip the clutch out just a skosh. Changing up through the gears, click, click; there are no rude clunks to spoil all of those nice clicks.

Even after several miles, considerable smoke continued to pour from the pipes.

Eventually it dried up for steady throttle cruising, but a burst of acceleration would renew the stream of blue smoke. Suzuki calls their automatic fuel/oil mixing system Crank Cylinder Injection (CCI). In this system, oil from a separate tank feeds a mechanically driven oil pump. Delivery rate from the pump is governed by both engine speed (rpm) and throttle opening. That way, the engine gets oil metered in direct proportion to the load to which it is subjected. For the GT series, a sub-system has been added to work in conjunction with the CCI. One-way valves in the bottom of the crankcases of each cylinder are connected to the transfer port of the right cylinder with small neoprene hoses, the theory being that any residual oil in the cases will be drawn into the cylinder and used faster than if the oil were allowed to be slowly washed out by the fuel/ air mixture. The way our bike smoked at the start, and continued to smoke, there must be some hitch in the scheme. Little puddles of oil collected in the ends of the mufflers after each ride.

Our first riding impression of the 380 was the unexpected smoothness of the engine. The feel is much like that of the GT-750, and for good reason: the engine is fastened to the frame via rubber shock mounts in both bikes. We think this mounting system is a good thing. The only bike having a similar system in the 350 comparison test (Cycle Dec. '70) was the Bridgestone GTR. In all the other 350s, we could feel all the little effects of secondary vibrations in the engine. The Bridgestone was the first bike we thought was "turbine smooth." The GT-750 Suzuki was the next. In the 380, you can feel the engine go through its stages of harmonic vibration, as the revs range, but the feeling is remote and very low-key. The only place that gets into really constant bothersome vibration is the passenger footrests. The footrest mounting bolts double as the rear muffler fasteners. There is a Silentbloc-type rubber mount on the mufflers, but the passenger pegs are on the muffler side of the rubber. As a result, the footrests shake really badly. The rider's footrests go through ranges of moderate tickle during hard acceleration, but are smooth at all cruising speeds. The remainder of the bike that touches the rider is free from bothersome vibration. The engine still shakes normally, but the rider doesn't feel it.

The GT-380J has a big motorcycle feel. Steering is slow and deliberate when compared to the 350s as a group, and light and responsive when compared to the 750s. Handling is great. Out in the mountains, twisting the bike as hard as possible, the 380's steering and suspension work in perfect harmony to provide a surprise-free ride. It's great fun: the throttle full open when you're not on the brakes, and thrashing on the pedal of that six speeder.

The only real catch in your throat comes when the center stand hangs up and you get into a big wing-ding. With the rear shocks jacked up to the firmest of the five possible positions, you can get the bike way over before that happens. The only aspect we found lacking was the brakes. The front brake is the same one that is used on the Suzuki 350 twin. It was adequate on that lighter bike, but incapable of handling the 380's seventy-five extra pounds.

At Lions Drag Strip, in Long Beach, we could tell that our bike wasn't sharp. Aside from the excess oil delivery and resulting smoke, the carburetion was not spot on. The machine was easy enough to ride: bring the revs up to 7000 and feed the clutch out just fast enough to give a little wheelspin. Our best time was a disappointing 14.94 seconds at 85.95 mph. We had a new Yamaha 350cc R5 and a new Kawasaki 350cc S2 along with us at the strip. They were completely new bikes, just uncrated, set up, and tuned. Our Suzuki was only slightly quicker than either of them.

Unfortunately, our test machine was a pilot-run production machine. Suzuki's technical people tell us that the oil pump problem and carburetor metering will be changed on later bikes, along with modified engine mount fittings that alleviate the slight vibration stages that bothered us. The first thousand 380s delivered to dealers will be modified with kits supplied by Suzuki.

Maintenance-easing techniques we noticed on the 750 are passed on to the 380. Ignition timing is quickly and easily set with built-in pointers. All three carbs have synchronizing plugs to aid in getting the slides to open at the same time. Too, the carbs are keyed to their individual rubber-mounting spiggots so that they can be instantly set parallel to the cylinder bores without fiddling with straight-edges. Wiring and control cables are tied to the frame and handlebars wherever necessary with those little plastic-covered bands.

Many handling complaints from bike owners of all brands have been traced to tire pressure ignorance. Even though the owner's manual explicitly gives this information, it often goes overlooked. To combat this problem, Suzuki and other makers are using stickers applied to their bikes that give the pressures for solo and passenger riding at both high and low speeds. Such stickers were on both sides of our bike.

Correlating with the different tire pressure requirements for varying condtions, we found that the shocks had to be adjusted in a like sequence. If the shock spring load was set high, the seams on the freeways would play hell with the rider's back. And if the springs were set soft, the center stand would scrape easily on moderate corners. The shocks are very easily adjustable, but require a tool. For this purpose, we kept one of the Phillips screwdriver blades from the 380's tool kit fastened to the handlebars with a rubber band. Inserting the blade in the deep sockets on the spring adjusters allowed them to be set quickly according to whatever kind of road we wanted to ride on.

The only maintenance hassle we ran into was a carryover from the GT-750. The 380 had a similar endless drive chain. So far, Suzuki has not developed a chain parting and connecting tool that is compact and economical enough for use by the average bike owner.

Our GT-380 was rather loud. Measured by our sound level meter, using the California Highway Patrol method, the bike recorded a shocking 93 dB(A).

Judging the GT-380J by its own declared standards, our bike came close to making it as an intermediate-size Gran Tourismo. Its weight/engine capacity ratio remains comparable to those of the better performing 350s, and it only insults its owner's euphoria when it comes to getting slowed down and speeded up in a hurry. At $925 plus the usual taxes and dealer costs, it's getting well into the cheaper 500cc price range. If the Sebring's problems get ironed out later in the production run, it might be worth it. And the problems aren't all that extensive: to fulfill its image as a Gran Tourismo, it needs more steam, a better front stopper, and more cornering clearance, so the rider can take maximum advantage of the 380's superior handling characteristics.

Source Cycle 1972