Contents: Adjusting idle speed and CO content… ↳ Checking and adjusting the fuel… ↳ Fast Idle Speed Adjustment ↳ Adjusting the air damper opening ↳ Adjusting the automatic starting… ↳
Adjusting idle speed and CO content in exhaust gases
Warm up the engine to operating temperature. Connect the gas analyzer and tachometer. Set the crankshaft speed to 3000 rpm. Hold it for about 30 sec and reduce the speed to idle speed. After the instrument needles settle, read the CO content and crankshaft speed. If necessary, adjust the speed with quantity screw 1 (Fig. 2.91).
In case of increased CO content, remove the air filter and remove the safety cap 2 of the quality screw using a screwdriver with a narrow blade. Raise the speed to 3000 rpm. Reduce it to idle and adjust the CO content in the exhaust gases by turning the quality screw for 30 sec. If the adjustment takes more than 30 sec., repeat the operation. Install a new safety cap on the quality screw and air filter and check the idle speed and CO content again.
Checking and adjusting the fuel level in the float chamber
Remove the carburetor, unscrew the six screws and remove the carburetor cover. Disconnect the rod from the automatic starting device. Holding the cover vertically, measure the distance between the cover gasket and the bottom of the float (Fig. 2.92).
If necessary, bend the float tongue. Attach the rod to the starting device and install the carburetor cover.
Fast Idle Speed Adjustment
Warm up the engine to operating temperature and connect the tachometer. Stop the engine, remove the air filter. Keeping the first chamber throttle valve in a partially open position, close the air flaps. Release the accelerator pedal; the starting device must be in the fast idle position. Release the air flaps without touching the accelerator pedal. Start the engine and read the tachometer. After releasing the air flaps, they must be in the fully open position. If this does not happen, either the engine is not warmed up enough or the starting device is faulty. Fast idle speed of 2700 rpm is adjusted with screw 1 (Fig. 2.93) after loosening the lock nut. After adjustment, install the air filter.
Adjusting the air damper opening
Disconnect the negative cable from the battery and remove the air filter. Disconnect the cable from the automatic starting device. Loosen the three fastening screws and remove the bimetallic spring housing and the internal heat-insulating nut. Place a rubber ring on the air damper drive lever and the carburetor housing to hold the dampers in the closed position (Fig. 2.94).
Then open the air flaps and release the accelerator pedal. Unscrew and remove the plug of the air flap pneumatic drive, use a screwdriver to push the plunger to the stop and use a round gauge or a 5.2-5.8 mm drill to measure the amount of air flap opening. To adjust this value, turn adjusting screw 2.
Adjusting the automatic starting device
With the throttle valve of the first chamber slightly open, turn cam 1 (Fig. 2.95) of the throttle valve control so that its protrusion rests against adjusting screw 2.
Release the accelerator pedal to lock the cam in this position. Close the air flaps until the cam protrusion stops in the adjusting screw, as shown in the figure. Using a round gauge or a 1.5-2.5 mm drill, measure the gap between the wall of the mixing chamber and the edge of the air flap of the first chamber. If necessary, adjust the gap by bending the tongue (Fig. 2.96).
