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1976-1981 Kawasaki JS400 Review and Specs [Video]

1976-1981 Kawasaki JS400 Review and Specs [Video]

The iconic Kawasaki JS400 was the first mass-produced Kawasaki Jet Ski in history. Although the world’s first PWC title is claimed by the 1968 Bombardier Sea-Doo, the JS400 was the ski that actually introduced this sport to the general public.

If you want to find out more about this legendary ski, this post is for you.

We at JetDrift have compiled all you need to know into this Kawasaki JS400 review!

1976-1981 Kawasaki JS400 Review

The history of the first Kawasaki Jet Ski goes back to the early ‘70s, when the prototypes were designed by Clayton Jacobson II.

Surprisingly, Jacobson was the same person who invented sit-down type PWCs in the ‘60s. Unfortunately, these odd machines never became commercially successful.

Once the patent expired, the inventor turned to the Japanese Kawasaki with his revolutionary idea. As a result of this cooperation, the first Kawasaki Jet Ski was released in late 1972.

It’s a fun fact that the manufacturer called this machine “Power Ski” and “Water Jet” before they merged these terms into the name “Jet Ski.”The first models were manufactured in a limited quantity under the names of 1973 WSAA and WSAB Kawasaki Jet Skis. They were built on a hand-laid fiberglass hull made in Japan and utilized a 2-stroke, 400cc twin engine.

The hull of the WSAA featured a relatively flat design while the WSAB had a convex v-shape.

These ancient machines were intended for racing and marketing purposes, which the manufacturer used in trying to promote this entirely new sport. And it did a very good job!

These sporty stand-up Jet Skis became more and more popular, gaining a huge fan base worldwide.

By 1976, Kawasaki had decided to start mass production of its stand-up Jet Ski, and the JS400 was born.

Let’s get down to the nitty-gritty and talk about this model in detail!

Kawasaki JS400 Hull and Top Deck

The Kawasaki JS400 is considered to be the world’s first commercially successful jet ski, and was manufactured from 1976 through 1981.

Although the predecessors WSAA and WSAB Jet Skis were made in Japan, production of the Kawasaki JS400 started in Lincoln, NE USA.

The top deck and the hull of the Kawasaki JS400 were Fiberglass Reinforced SMC. In terms of dimensions, the ski measured 84.3 inches in length, 24.4 inches in width, and 25.2 inches in height, while its weight was only 244 pounds.

The ski was so light that 3-4 people could even launch it by hand!

The top deck and the tray of the JS400 were much narrower than today’s large stand ups. As an example, the latest Kawasaki SX-R 160 is 30.1 inches wide while the JS400 was only 24.4 inches wide.

And that’s a huge difference!

Kawasaki JS400 vs. SX-R 160The inner side of the rails was not covered with deck mats, which resulted in a poor grip between the machine and the rider’s legs.

The handlebar pole also lacked any padding and housed very narrow handlebars. What’s more, the bars were positioned at an awkward angle, forcing the rider’s elbows close to their body.

The ski housed a tiny, 3.5-gallon fuel tank and a fire extinguisher compartment mounted in the left rail.

Kawasaki JS400 Engine and Propulsion

The power source of the Kawasaki JS400 was a purpose-built 2-stroke, 400cc, vertical twin Kawasaki marine engine rated at 24.5 HP.

The key advantage of this power source was its open-loop water cooling system, which ensured an adequate engine temperature regardless of the outside temperature.

In contrast, the first Sea-Doo PWCs utilized air-cooled engines, which were prone to overheating. Among other issues, this contributed to their rapid downfall.

The JS400 also featured a single diaphragm type, BN38 Mikuni carburetor but lacked any oil system. Instead, it had to be fueled with a gas/oil premix.The propulsion system of the ski was a 121mm axial-flow, single-stage jet pump, featuring a 6-vane stator and a 3-blade, aluminum impeller.

This advanced propulsion system offered a maximum thrust of 220 pounds.

Surprisingly, the exhaust pipe of the ski protruded out of the front portion of the top deck, which looked very weird.

Kawasaki JS400 Features

As one might expect, the JS400 only came with a few standard features.

It only had a very basic control panel planted in the front of the tray, housing a start/stop button, a choke knob, and a fuel valve.

The awkward position of the stop button made the engine difficult to turn off as you approached the dock or beach.

What’s more, the JS400 lacked a safety lanyard, meaning that the engine didn’t stop automatically if you fell into the water. Instead, after a fall the jet ski started to slowly circle in the water and you literally had to catch it to reboard.

Let’s face it, this was neither safe nor convenient!

This is why today’s jet skis feature a safety lanyard that automatically stops the engine in case of a fall.

The JS400 also lacked any instruments or electrical systems, which make today’s jet skis so complex.

Kawasaki JS400 Performance

Despite its moderate engine performance, the top speed of the JS400 was about 31 mph under ideal conditions.

Although this seems fairly slow compared to the speed of the latest machines, in the ’70s it was an impressive speed for a jet ski!

The JS400 was also extremely nimble due to its slim top deck and narrow tray, so riding it required a ton of skills and a good sense of balance, not to mention the reboarding process, which also required a lot of practice.

Unlike today’s sit-down jet skis (a.k.a. “couches”), the JS400 was definitely not for everyone. This ski was intended for racers and avid sport enthusiasts who had the necessary expertise and athletic skills.

As reported by, as the old saying goes:“If you knew how to ride a JS400 well, you could ride any type of stand-up in the future.”The JS400 was in production until late 1981 when it was replaced by the more advanced JS550.

Besides the JS400, Kawasaki also marketed its more powerful brother, the JS440 from 1977.

Kawasaki JS400 Specs Charts

For your convenience, we’ve compiled the key specs of the 1976-1981 Kawasaki JS400 into these charts:

Kawasaki JS400 Engine Specs

Kawasaki JS400Engine Specs
Engine type2T, vertical twin, water-cooled
Displacement400 cc
Bore x stroke (mm)65 x 60
Power (hp / rpm)27 / 4,500
Compression ratio7.0 : 1
Fuel induction system1 x Mikuni BN38 diaphragm type
Exhaust systemCast exhaust wet pipe with a 2-1 header
Cooling systemEngine-Exhaust-Open loop system
Fuel consumption (L/h)5.7 L /hr (1.5 US gal/hr at 32 kph)

Kawasaki JS400 Drive System

Kawasaki JS400Drive System
PumpAxial flow, single stage, 6 vane stator
Pump diameter121 mm
Thrust100 kg (220 lb)
Impeller3-blade, aluminum

Kawasaki JS400 Dimensions

Kawasaki JS400Dimensions
Overall length84 in (2133 mm)
Overall width24 in (610 mm)
Overall height25 in (635 mm)
Hull materialfiberglass reinforced SMC
Deck materialfiberglass reinforced SMC
Weight111 kg (244 lbs)

Kawasaki JS400 Fuel and Oil

Kawasaki JS400Fuel and Oil
Recommend fuelRegular unleaded gasoline, 87+ octane rating
Fuel capacity3.5 US gal (13 L)
LubricationGas/Oil pre-mix 32:1 ratio
These charts are for informational purposes only! For exact specifications, please refer to the factory manual.


As a takeaway, we’ve answered the most common questions about the 1976-1981 Kawasaki JS400!

What is a Kawasaki JS400?

The Kawasaki JS400 was the first mass-production Kawasaki Jet Ski.

When did the Kawasaki JS400 Come Out?

The Kawasaki JS400 debuted in 1976.

What Years Did Kawasaki Make the JS400?

Kawasaki marketed the Kawasaki JS400 from 1976 through 1981.

What Size was a Kawasaki JS400?

The Kawasaki JS400 measured 84.3 inches in length, 24.4 inches in width, and 25.2 inches in height, while its draft was 8 inches.

How Much Did a Kawasaki JS400 Weigh?

The dry weight of the Kawasaki JS400 was only 244 pounds.

How Many People Could Ride on a Kawasaki JS400?

The Kawasaki JS400 could carry only one adult rider.

What Kind of Engine was in the Kawasaki JS400?

The Kawasaki JS400 was powered by a 2-stroke, 400cc, vertical twin Kawasaki marine engine.

Was the Kawasaki JS400 Supercharged?

The Kawasaki JS400 was powered by a naturally-aspirated engine.

Was the Kawasaki JS400 a 2-stroke?

Yes, the Kawasaki JS400 was powered by a 2-stroke engine.

How Much Horsepower Did a Kawasaki JS400 Have?

The Kawasaki JS400 produced 24.5 HP.

How Much Oil Did a Kawasaki JS400 Hold?

The Kawasaki JS400 didn’t have an oil system as it ran on premix.

How Much Fuel Did a Kawasaki JS400 Hold?

The Kawasaki JS400 was equipped with a 3.5-gallon fuel tank.

How Much Fuel Did a Kawasaki JS400 Use?

The claimed fuel consumption of the Kawasaki JS400 was about 1.5 GPH at 20 mph.

What was the Fuel Range of the Kawasaki JS400?

The fuel range of the Kawasaki JS400 was about 47 miles at 20 mph.

How Fast Did a Kawasaki JS400 Go?

The top speed of a Kawasaki JS400 was about 30-31 mph under ideal conditions.

Did the Kawasaki JS400 Have a Reverse?            

No, the Kawasaki JS400 didn’t have a reverse system.

Did the Kawasaki JS400 Have a Brake?

No, the Kawasaki JS400 was manufactured without a brake system.

How Much Does a Kawasaki JS400 Cost?

The asking price of a used Kawasaki JS400 varies between $1,000 and $3,000 depending on the year and its condition.