Restart a Solex

For solex that are in good condition but whose engine does not work, a simple cleaning is often enough to restart.

Engine blocked?

Solex engines are relatively easy to restart if the piston is not stuck in the cylinder. To verify this, remove the magnetic flywheel cover and turn the handwheel by hand or by pushing the Solex, engine in gear. The engine must turn and have hard points that are the compression times. It also verifies that the segmentation of the piston is good. If the magnetic flywheel turns in a vacuum, the molded flywheel key and clutch will be checked.

Be careful that the engine does not start with your hand on the magnetic steering wheel !!!


In the case where the engine is not blocked and has good compression, the first step is cleaning or changing the spark plug. Its replacement must absolutely be by a candle of the same characteristics to prevent the part inside the cylinder comes into contact with the piston during its ascent. To access the candle, simply remove the air filter. A possible test to verify that the ignition components are still good is to put the high voltage wire on the spark plug and put his lower body in contact with the cylinder. By turning the engine (two: one pushes the Solex, the other holds the candle in position with an insulating clip) sparks should be visible. Otherwise, the magnetic flywheel must be disassembled with an extractor to allow the cleaning of the platinum screws, or even the change of the capacitor (available new at Solex dealers).

Fuel supply

The second step is the cleaning of the gasoline circuit and in particular the tank, the pump and the nozzle. These organs are often in good condition but the oil contained in the gasoline is slowly deposited with the years of non-use. The jet is the only screw on the carburetor behind the cylinder. It is written generally Solex. It is cleaned in gasoline and then with a blow of compressed air. The fuel pump is on the front of the engine. There are four screws to disassemble. Attention to their reassembly, they do not support a big tightening. A cleaning with the essence of the pump and the membrane is enough. Tank cleaning is extremely important. It must be removed, emptied of its contents, and cleaned with water under pressure for example and rinsed with gasoline before reassembly. Be careful not to damage the small filter at the bottom, accessible by the pipe between tank and pump.


After checking the brakes (it will not go very fast but good ...!) And refuel with gasoline with 3% oil 2T, there is more than push the Solex, engine in the low position, decompressing with the handlebar control on the first meters. The choke is the small tongue behind the air filter. Completely pushing left, the mixture is richer in gasoline, pushed right, the mixture is less rich. Depending on the outside temperature and that of the engine, it will play with this tab. A mix too rich will not go fast and the engine will be bridled. If the engine refuses to start or if its rhythm is not regular, it will have to go further in the disassembly.
Disassembling the spark plug directly after the start attempt will indicate whether the mixture reaches the cylinder (wet candle).
The spark test is to be done if it has not been done before.

Poor performance can come from worn segmentation. There are relatively cheap devices for measuring compression ratios.