Idle speed adjustment must be performed on a warm engine (at a coolant temperature of 90–95°C), with adjusted valve timing clearances, with the ignition timing set correctly, and with the air damper fully open.
Using the adjusting screw 1 for the mixture quantity, the crankshaft speed is set according to the stand tachometer within 820-900 min⁻¹. Then, using the adjusting screw 2 for the mixture quality (composition), the concentration of carbon monoxide (CO) in the exhaust gases is achieved within 0.5-1.2% at the given position of screw 1 (the CO concentration is brought to 20°C and 760 mm Hg). Using screw 1, the crankshaft speed is restored to 820-900 min⁻¹. If necessary, using adjusting screw 2, the CO concentration is restored to 0.5-1.2%.
After completing the adjustment, sharply press the throttle pedal and release it. The engine should increase the crankshaft speed without interruption, and if it decreases, it should not stall. If the engine stops, use screw 1 to increase the crankshaft speed within 820-900 min⁻¹.
After adjustment, install a new plastic plug into the hole of the adjusting screw 2.
Note: When screw 2 of the mixture quality is unscrewed, the combustible mixture becomes leaner; when screwed in, it becomes richer.