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Suzuki GT380 model history
1972—1978


I have tried to tell the model history of the Suzuki GT380 as I know it. I would be grateful of any contributions — sales brochures, magazine ads, magazine articles, pictures, specs, facts, corrections etc. Please scan the material in JPEG format (large enough that all the details are visible) and send them to me. Please tell me the source and the publication date if possible. If you send me pictures of your own bike, please follow these instructions.

Suzuki launched its air-cooled two-stroke triples GT380 and GT550 in 1972. An water-cooled three-cylinder GT750 had already been presented a year earlier and the 380 and 550 followed the design of the flagship model.

The GT380 and GT550 were predicatable and sporty motorcycles, but up to a point. At touring speeds they were comfortable and smooth, but twisting the grip farther brought a wobble and cornering at higher speeds showed the limitations of the suspension, swinging arm and the tube frame.

The GT engines were less highly tuned than for example the Kawasaki triples. It was tuned for the long run. Porting, timing, compression, carburetor size etc. were all chosen to deliver smooth power at the expence of maximum power. It made the Suzuki GTs more reliable than fast. The odd 3 to 4 exhaust system and rigid foot pegs also limited the leaning angle and the sporting nature of the bike. The GT triples were simply made for touring and not for sport-styled riding.

The Ram Air System (introduced in all of the air-cooled GT models) that forced the cool air to pass through the cylinders and behind the block was a new developement, tested earlier on Suzuki's TR500 racers. It is an simply an air scoop that ducts cold air directly onto the cylinder head the help the cooling on the engine. It was a known problem that two-stroke engines lost power when the cylinder head temperature rose too much. Cooling problem plagued other two-stroke triples but the Ram Air System made the Suzuki GT triples less suspective to the charasteric two-stroke power loss caused by too high a cylinder head temperature after a long, hard run. Nevertheless the GT triples still had a reputation for the middle piston seizing.

Suzuki's automatic system mixing fuel and oil had been refined for the GT models, providing less exhaust smoke, now called CCI. A clever new item in the early seventies was the vacuum-operated petcock was first used on the GTs and later used on all Suzuki mototrcycle models.

Both triples saw some minor improvements every year of their production but after only few of years production the two-stroke engined street bikes were terribly out of fashion. Although the GT380 was as strong and reliable as a four-stroke of equal displacement the rather high fuel comsuption of the two-strokers was suddenly an issue, when the gasoline prizes rose in the seventies. Even Suzuki itself dug a grave to its two-stroke models by launching its highly popular GS series with four-stroke angines. It was actually forced to change their minds and start making four-stroke engines. The tighter emission regulations in America sounded the death knell for most two-strokes.

The GT550 was discontinued in 1977 and the GT380 a couple of years later, in 1979.
 



Suzuki 1972More Suzuki models from 1972
1972 Suzuki year code: J
 
The 1972 GT380J was square-bore and stroke of 54 x 54 mm with 6,7 :1 compression ratio. Fuel was fed via three Mikuni VS24SC carburettors and maximum power was claimed 38 bhp at 7,500 rpm. It had a six speed gearbox and starting was kickstart.

The GT380 was a massive bike with a rigid chassis with standard telescopic forks up front and twin oil-damped shockers mounted on tubular steel swinging arm. The brakes were a 180 mm double-leading drum brake at the front and 200 mm rear. It had 19-inch spoke wheels front and 18-inch rear and somewhat anorectic 3.00 front tire and 3.50 rear tire. The front brake proved to be at its best only adequate and was replaced with a disc brake the following year.

large fuel tank and saddle with plenty of room for riding with a passenger. Unfortunately the engine vibrations were transmitted to the passenger footpegs making the ride less comfortable for the passenger as it was for the fellow in front of him.

The fuel tank cap had a lock in it, an unusual feature at the time, as was the rubber lip seals for the spark plugs, keeping moisture from shorting out the system.

The cylinders of the GT380 were cast as three separate units and ech piston was fitted with a not-removable cast-in iron liner. The cylinder head was cast in one piece.

Presented in January 1972 (Japan). A revised model (B1) was released in April 1972 (Japan).
Intitial frame number: GT380-10001
 
GT380J GT380 GT-380GT 380 J 1972
Overall Length: 2 090 mm (82.3 in)
Overall Width: 800 mm (31.5 in)
Overall Height: 1 100 mm (43.3 in)
Wheelbase: 1 380 mm (54.3 in)
Weight: 183 kg (402 lbs)
Engine type: Air-cooled 371 cc inline-3, 2-stroke. 38 hp/ 7.500 rpm, 3,8 kg-m/ 6.500 rpm.

Click on the image for larger format.


Suzuki 1973More Suzuki models from 1973
1973 Suzuki year code: K

 
The 1973-year's GT380K had a 275 mm brake disc at the front, mounted on the right side of the wheel with the caliper in front of the fork leg. It was and improvement compared to the drum brake — if the weather was dry. The early Japanese disc brakes were hopeless in the wet. A warning sticker was attached to the fork leg saying ”Caution — braking performance at beginning of the apllication may change with wet brake disc”. Modern brake pads and Goodridge hoses can improve the original braking power and cure sponginess.

Some changes were made to the frame and exhaust system to provide more ground clearance and reduce vibration.

Presented in April 1973 (Japan, B3).
Intitial frame number: GT380-30919
 

Suzuki GT-380 K GT380K GT380 GT-380 street bikeGT 380 K 1973
Overall Length: 2 105 mm (82.9 in)
Overall Width: 850 mm (33.5 in)
Overall Height: 1 100mm (43.3 in)
Wheelbase: 1 355 mm (53.3 in)
Dry Weight: 171 kg (376 lbs)
Engine type: Air-cooled 371 cc inline-3, 2-stroke. 38 hp/ 7.500 rpm, 3,9 kg-m/ 6.000 rpm. 6 speeds.

Click on the image for larger format.
Here's even larger picture.


Suzuki 1974More Suzuki models from 1974
1974 Suzuki year code: L
 
The 1974-year's GT380L had different carbs than all the other models. The carburettors were changed to constant velocity type along with a change to the air filter box whick meant that the 380 lost one norsepower. A cooling fan was available as an option. Final drive sprockets were changed to raise the gearing and a gear indicator was fitted to the instruments. The Ram Air cover took an smoother shape and lost its fins. Headlight brackets and shell were now chromed as was the chaingueard and airbox. The earlier gunmetal alloy finish of the engine became natural lacquered alloy. The dummy airscoops were removed from the side panels.

Presented in January 1974 (Japan, B3).
Intitial frame number: GT380-43732
 
Suzuki GT-380 GT380LGT 380 L 1974
Overall Length: 2 105 mm (82.9 in)
Overall Width: 850 mm (33.5 in)
Overall Height: 1 100mm (43.3 in)
Wheelbase: 1 355 mm (53.3 in)
Dry Weight: 171 kg (376 lbs)
Engine type: Air-cooled 371 cc inline-3, 2-stroke. 37 hp/ 7.500 rpm, 3,9 kg-m/ 6.000 rpm. 6 speeds.

Click on the image for larger format.
Suzuki GT-380 GT380LGT 380 L 1974
Overall Length: 2 105 mm (82.9 in)
Overall Width: 850 mm (33.5 in)
Overall Height: 1 100mm (43.3 in)
Wheelbase: 1 355 mm (53.3 in)
Dry Weight: 171 kg (376 lbs)
Engine type: Air-cooled 371 cc inline-3, 2-stroke. 37 hp/ 7.500 rpm, 3,9 kg-m/ 6.000 rpm. 6 speeds.

Click on the image for larger format.
Here's even larger picture.


Suzuki 1975More Suzuki models from 1975
1975 Suzuki year code: M
 
The GT380M model saw the carburettors revert back to the previous slide type. Otherwise the model remained virtually unchanged, except for a new color scheme. The Canadian model (see the picture below) didn't seem to have a grab rail behind the seat.

Presented in October 1974 (Japan, B4).
Intitial frame number: GT380-65984
 
Suzuki '75 GT-380 M GT380M GT380 GT-380 street bikeGT 380 M 1975
Overall Length: 2 105 mm (82.9 in)
Overall Width: 850 mm (33.5 in)
Overall Height: 1 100mm (43.3 in)
Wheelbase: 1 355 mm (53.3 in)
Dry Weight: 171 kg (376 lbs)
Engine type: Air-cooled 371 cc inline-3, 2-stroke. 38 hp/ 7.500 rpm, 3,9 kg-m/ 6.000 rpm. 6 speeds.

Click on the image for larger format.
Here's even larger picture.


Suzuki 1976More Suzuki models from 1976
1976 Suzuki year code: A
 No changes were made for the 1976 yaer's GT380A. In 1976 the GT380 was concidered as an old-fashioned bike from the early sevennties while its rivals were not. There was nothing wrong with the bike, the engine was nice and its power band was nearly as wide as the rev range, the clutch was easily controlled and the shifts were quick and precise. The sixth gear was a cruising gear, good for long flat streches and when the rider needed more power in hands the fifth worked well with not much extra fuel consumption. The handling was considered excellent within the bike's limitations. It was stable and steered well. Te original suspension didn't react properly on small irregularities but that was a minor problem. The problem was that the GT380 looked like an old bike and performed like an old bike. Its rvals, like Honda CB400F, Yamaha RD400C and Kawasaki KH400 looked new, had alectric starters, cast wheels, were lighter, faster and better handlers.

You could read in the Cycle World magazine in 1976: ”The GT380 is like going to the movies with your sister: Nothing wrong with it, but more exciting alternatives spring readily to mind.”

Presented in February 1976 (Japan, B5).
Intitial frame number: GT380-86754
 
GT380A GT-380A GT380 GT-380GT 380 A 1976
Overall Length: 2 090 mm (82.3 in)
Overall Width: 815 mm (32.1 in)
Overall Height: 1 125 mm (44.3 in)
Wheelbase: 1 385 mm (54.7 in)
Ground Clearance: 140 mm (5.5 in)
Dry Weight: 183 kg (402 lbs)
Engine type: Air-cooled 371 cc inline-3, 2-stroke. 38 hp/ 7.500 rpm, 3,8 kg-m/ 6.500 rpm.

Click on the image for larger format.
GT380A GT-380A GT380 GT-380GT 380 A 1976
Overall Length: 2 090 mm (82.3 in)
Overall Width: 815 mm (32.1 in)
Overall Height: 1 125 mm (44.3 in)
Wheelbase: 1 385 mm (54.7 in)
Ground Clearance: 140 mm (5.5 in)
Dry Weight: 183 kg (402 lbs)
Engine type: Air-cooled 371 cc inline-3, 2-stroke. 38 hp/ 7.500 rpm, 3,8 kg-m/ 6.500 rpm.

Click on the image for larger format.
GT380A GT-380A GT380 GT-380GT 380 A 1976
Overall Length: 2 090 mm (82.3 in)
Overall Width: 815 mm (32.1 in)
Overall Height: 1 125 mm (44.3 in)
Wheelbase: 1 385 mm (54.7 in)
Ground Clearance: 140 mm (5.5 in)
Dry Weight: 183 kg (402 lbs)
Engine type: Air-cooled 371 cc inline-3, 2-stroke. 38 hp/ 7.500 rpm, 3,8 kg-m/ 6.500 rpm.

Click on the image for larger format.


Suzuki 1977More Suzuki models from 1977
1977 Suzuki year code: B

 
The GT380 was still selling quite well in various parts of the world but the number of units built had dropped to less than 10,000 units a year, compared to the 30,000 units in 1972. Only cosmetic changes were made to the 1977-year's GT380B.
The models between 1975 and 1978 looked a lot like each other but the 1977 model can quite easily be identified for its Black (not color matching) side covers.

Presented in February 1977 (Japan, B6).
Intitial frame number: GT380-95063
 
Suzuki GT380B GT-380B Gt380 GT-380GT 380 B 1977
Overall Length: 2 090 mm (82.3 in)
Overall Width: 815 mm (32.1 in)
Overall Height: 1 125 mm (44.3 in)
Wheelbase: 1 385 mm (54.7 in)
Ground Clearance: 140 mm (5.5 in)
Dry Weight: 183 kg (402 lbs)
Engine type: Air-cooled 371 cc inline-3, 2-stroke. 38 hp/ 7.500 rpm, 3,8 kg-m/ 6.500 rpm.

Click on the image for larger format.


Suzuki 1978More Suzuki models from 1978
1978 Suzuki year code: C
 
1978 was the last year the GT380 was manufactured. Again, color matching side covers.

Presented in April 1978 (Japan, B7).
 
Suzuki GT380C GT-380C GT380 GT-380 '78GT 380 C 1978
Overall Length: 2 090 mm (82.3 in)
Overall Width: 815 mm (32.1 in)
Overall Height: 1 125 mm (44.3 in)
Wheelbase: 1 385 mm (54.7 in)
Ground Clearance: 140 mm (5.5 in)
Dry Weight: 183 kg (402 lbs)
Engine type: Air-cooled 371 cc inline-3, 2-stroke. 38 hp/ 7.500 rpm, 3,8 kg-m/ 6.500 rpm.

Click on the image for larger format.




More: Suzuki GT380 brochures

More: Suzuki GT models

More: All Suzuki models

Sources: Cycle World (USA), Classic & Motorcycle Mechanics (UK) etc.

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