Start the engine and bring the crankshaft speed to 3000 rpm, then release the accelerator pedal. Throttle stop screw (shown in the photo by an arrow) should return to the position of the engine speed drop after a short period of time, i.e. rest against the stop. At the same time, a change in air pressure should be felt in pipe 2.
If the air pressure does not change, check the tightness of the hoses and their connection to the carburetor 3. If the hoses are in good condition, replace the air valve 1 of the engine braking system.
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