What is Solex Carburetor?- Construction and Working

What is Solex Carburetor?

Solex is a French manufacturer of carburetors and the powered bicycle VéloSoleX. Solex carburetors were used by many European automobile companies and were licensed to Japanese maker Mikuni.

Originally the carburettor to Solex was built for cars. Later, under this name, the Solex was built as a motor-assisted bicycle.

As on any transportable, the carburettor is an important part. The solex carburettor doesn’t wear out quickly. It regularly happens that the nozzle of the Solex carburetor is clogging, especially when there is dirt in the fuel tank. The thread of the carburetor sometimes becomes damaged, usually by repairing incorrectly.

Solex carburetors were widely used by many European makers and under license to Mikuni in Asia until the mid-1980s when fuel injection was widely adopted.

Among the European companies who used Solex carburetors were: Rolls-Royce Motors, Alfa Romeo, Bristol, Fiat, Audi, Ford, BMW, Citroën, Opel, Simca, Saab, Renault, Peugeot, Lancia, Land Rover Series, Lada, Mercedes Benz, Volvo, Volkswagen, and Porsche.

Engineering Choice The Biggest Learning Platform

Solex carburetors have been made under licence by a number of companies including Mikuni of Japan which entered into a licensed manufacturing agreement with Solex in 1960 and further developed many of Solex’s original designs.

Japanese automakers and motorcycle manufacturers using Mikuni carburetors included: Toyota, Mitsubishi, Suzuki, Nissan, and Yamaha.

Construction of Solex Carburetor

 Solex Carburetor

In Solex Carburetor, the Fuel chamber is the part that collects fuel from the fuel tank and stores it to create an air-fuel mixture in the carburetor. This fuel chamber has a float that is used to maintain the level of fuel in the fuel chamber.

There is a mainline through which the fuel reaches the venturi throat tube. The fuel enters the venturi throat tube from the main jet which is located at the end of the mainline. The fuel from the main jet gets air when the choke opens. Fuel from the main jet mixes with air which comes when the choke is opened to form an air-fuel mixture and this air-fuel mixture reaches the engine cylinder when the throat valve opens.

Apart from the main jet, there is three more pipelines through which the engine cylinder gets fuel, they are pilot jet, pump jet, and starting passage.

Pump jet gets fuel from the acceleration pump and the pilot jet gets fuel from the main jet. The pipeline of the pilot jet is separated from the mainline.

The acceleration pump is operated using an acceleration pedal. This acceleration pump is used during acceleration.

A pilot jet is used during the idle or no-load condition. It has a pilot bleed orifice from which the pilot jet gets air to form an air-fuel mixture. Near the end of the idle condition pipeline, there is an Idling Screw which is used to control the amount of air-fuel mixture to be passed to the Engine Cylinder.

Starting passage gets its fuel from Starting Circuit or Bi-Starter. This starting circuit is used to supply the air-fuel mixture during the starting time. This starting circuit has a flat disc that has holes of different radius which is used to control the amount of fuel supply during starting.

This starting circuit also has Air venturi which supply air in the starting circuit to create an air-fuel mixture. The air-fuel mixture from starting circuit is supplied to the engine cylinder through starting passage which is present below the throttle valve.

Working of a Solex Carburetor

At the time of starting, bigger holes connect the passage so that more fuel may go to the engine. The throttle valve is closed, the whole engine suction is applied to the starting passage

  • The petrol from the float chamber passage through the starter petrol jet and rises into passage
  • It comes out and mixes with the air entering through the air jet. This air-fuel mixture is rich enough for starting the engine.

After the engine has started, the starter lever is taken to the 2nd position. So that smaller holes connect the passage reducing the amount of petrol. In this position, the throttle valve is also partly open so that the petrol is also coming from the main jet.

The reduced mixture supply from the starter system in this situation is however sufficient to keep the engine running. When the engine reaches the normal temperature, the starter is taken to the “off” position.

Advantages of Solex Carburetor

  • All circuits for different conditions works separately.
  • It minimizes waste and reduce carbon formation.
  • Throttle response is high as compared to other carburetors.
  • It works perfectly under sudden heavy acceleration requirements.
  • It starts very easily.