Czechoslovak "Java 634" - a vivid memory from the past

Starting in the mid-70s and ending with the 90s, Java 634 was considered the best motorcycle in the Soviet Union. Production was carried out on the territory of the brotherly state of Czechoslovakia from 1973 to 1984. The domestic market was the main consumer of the plant’s products. The main advantages include good technical and operational characteristics, high quality of parts and assemblies. Another advantage of the Soviet era was that the motorcycle was imported.

general description

Like most motorcycles of that time, the Java 634 was a two-wheeled vehicle and was designed to carry no more than two people (with a driver). Alternatively, a side hitch (cradle) or rear trailer was attached.

Maximum speed - up to 170 km / h, fuel consumption of 3.9 liters per 100 km in the combined cycle. The engine ran on gasoline, which was mixed with oil in a ratio of 1 to 30.The special uniform and low rumble during the work of the motorcycle made it possible to distinguish it from the Soviet competitors of the time.


Push pullThe engine "Java 634" is a two-cylinder volume of 350 cm3, the name of the series 350 came from it. The maximum power was 22 horsepower, and the torque is 3 kg / m. Due to the correct location of the cylinders relative to the axis of the motorcycle, the air cooling system worked very well, the engine overheating was almost impossible. In total, with such power units 5 modifications were released:

  • Jawa 350 633;
  • Jawa 350 634;
  • Jawa 350 638;
  • Jawa 350 639;
  • Jawa 350 640.

Java 634

The layout of the motorcycle "Java 634" block: body, crankcase, clutch and gearbox are made in one case. The metal from which the motorcycle cylinders are made is gray cast iron, the piston and cylinder head are alloy. Each piston has three compression rings. Steel fingers are mounted on a needle bearing and secured to the piston using wire locks. Cranks and bushings are made of steel forged. Flywheels, fingers and pins in the general assembly are combined in the crankshaft.

Repair java 634


A distinctive feature that Java 634 acquired relative to the previous model is the updated frame. It was attached to the swinging fork and the front wheel.The design is made of metal rounded pipes, interconnected in several places. The design took place taking into account the subsequent attachment to the motorcycle side stroller or rear trailer, for this there are special holes.

Java engine 634


In principle, the work of the four-speed gearbox is nothing complicated. The link, which controls the position of the two forks, creates four variations of the closing mechanical circuit between the primary and secondary shaft, in simple words, switches to one of the four gears. When you turn on any speed, the remaining gears work in idle mode, and do not stand still.

With proper operation, the motorcycle "Java 634" was able to carry its owner 100,000 km without problems. But improper gear shifting, as well as a rude relationship with the technique could lead to the departure of gear after 10,000 mileage. This gearbox malfunction was very frequent when buying with hands.

At the time of switching the gear shift gears along the shaft no more than five mm. When working out the working surface increases the load and reduces the life of the parts.As a result, the cams are not constrained in the coupled state and are disconnected under the influence of gears. Thus, there is a spontaneous shutdown of the transfer to the "neutral".


Fitted single-chamber carburetor with a horizontal flow of gasoline. The metal from which the entire assembly was made was aluminum alloy. Like most motorcycles of the socialist era, after running it required additional adjustment. It was implemented as follows:

  • The needle was rearranged from the fourth to the third groove.
  • The adjusting screw of the idling needed to be unscrewed by 0.5-1.5 turns (at the time of running-in, it was unscrewed by half a turn).

Carburetor java

Sometimes the engine could start a little "stupid" during acceleration, the culprit was the carburetor. “Java 634” was equipped with a part bearing the marking 2926 SBDB, which is very sensitive to the quality of the fuel, so it was necessary to thoroughly wash the carburetor several times with gasoline. After that, you could again enjoy riding a Czechoslovak motorcycle.


Simultaneously with the release of motorcycles for the Soviet consumer, the national enterprise produced equipment for the domestic market.Since in Western European countries such products were considered obsolete, the equipment was calculated only for sales within Czechoslovakia.

The peculiarities of the Czechoslovak "Java" include the reduced engine power (20 l / s, 14.7 kW). This was done in order not to exceed the noise level of 84 dB. The model was marked 634/4/03. Recall that for the Russian market a motorcycle was produced with a capacity of 22 hp.

Nostalgia about the past

Motorcycle java 634

The model was produced for 10 years, and during this time more than 100,000 units were delivered to the territory of our country from Czechoslovakia. That 634 model was the last "six-volt", replaced by a motorcycle with onboard voltage of 12 V, modification 638.

Despite the fact that production was completed more than 30 years ago, sometimes there are quite well-preserved specimens on the road. Some people just keep the bike in the garage as a memory of those years, take a ride a couple of times a year, carefully monitor and make the necessary repairs.

"Java 634" (motorcycle) can be called a technique from the Soviet past of our country, which, unfortunately, is almost gone!

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