Adjusting the fuel level in the float chamber
Remove the carburetor cover and turn it over.
Measure the distance between the plane of the carburetor cover and the lower point of the floats, which for the 1st chamber should be within 28±1 mm, for the 2nd chamber - 30±1 mm. If it does not correspond to this, set the desired size by bending the tongues of the float levers.
Cold idle adjustment
Warm up the engine to operating temperature.
Connect tachometer.
Stop engine.
Remove air filter.
Open the throttle valve of the 1st chamber and close the choke valve by depressing the cam at-throttle opening (see photo).
Release the throttle valve of the 1st chamber.
Start the engine without depressing the accelerator pedal.
Measure the crankshaft speed, which should be between 3350-3450 rpm for vehicles with manual transmission and 3550-3650 rpm for vehicles with automatic transmission.
If necessary, adjust the opening of the throttle valve of the 1st chamber with a restrictive screw resting on the profiled throttle valve opening cam.
Air damper starting gap adjustment
Remove starter cover.
Fully open the throttle valve by placing the throttle valve opening cam on the appropriate profile.
Connect a vacuum gauge and a vacuum pump to the air damper actuator and create a vacuum of 100 mbar in the pneumatic actuator.
If the air damper actuator is sealed, the vacuum must not decrease by more than 5 mbar per minute and must not fall below 40 mbar.
Bring the vacuum in the pneumatic actuator of the air damper to 200-300 mbar.
Use a set of feeler gauges to measure the starting gap of the first stage of the air damper, which should be within 1.8±0.15 mm.
If necessary, set the required gap with the screw for adjusting the stroke of the pneumatic actuator diaphragm located on its cover.
Close the atmospheric opening of the air damper pneumatic actuator with a plug, create a vacuum of 200 mbar in the pneumatic actuator, which, if the pneumatic actuator is tight, must remain unchanged for at least 1 minute.
Use a set of feeler gauges to measure the starting clearance of the second stage of the air damper, which should be within 3.9±0.15 mm for vehicles with a manual gearbox and 3.7±0.15 mm for vehicles with automatic transmission.
In case of deviation from the norm, set the proper clearance with the adjusting screw of the pneumatic actuator diaphragm travel located on the end of the air damper actuator rod.
Throttle opening adjustment of the 1st chamber
The throttle position of the 1st chamber is adjusted at the factory, however, if the adjustment is incorrect, it can be restored as follows:
- remove the plug of the throttle stop screw;
- remove the stop of the throttle control lever from the profiled choke control lever, fully opening the choke for this;
- unscrew the limit screw so that it does not touch the throttle control lever;
- open throttle;
- screw in the stop screw until it touches the throttle control lever, then screw it in another 1/4 turn. If the throttle opening is adjusted correctly, the gap between the limit screw and the throttle control lever should be 0.05 mm;
- install a new plug on the throttle stop screw.
Throttle opening adjustment of the 2nd chamber
The throttle position of the 2nd chamber is adjusted at the factory, however, if the adjustment is incorrect, it can be restored as follows:
- unscrew the restrictive screw of the throttle valve of the 2nd chamber so that it moves away from the stop, then screw in the restrictive screw so that it barely touches the stop;
- disconnect the rod from the pneumatic actuator of the throttle valve of the 2nd chamber;
- screw in the limit screw ¼ turn;
- lock the limit screw with special glue or paint.
Accelerator pump adjustment
Remove carburetor.
Fully retract the movable stem of the 1st chamber throttle actuator and turn the cam of the 1st chamber slightly opening the throttle valve so as to release the throttle valve and fully open it.
Place a beaker under the carburetor.
Smoothly fully open and close the throttle valve of the 1st chamber ten times, thereby activating the accelerator pump.
Measure the amount of fuel in the beaker, which should be 10±1.5 cm3, i.e. 1.0±0.15 cm3 for one cycle.
If necessary, adjust the desired performance of the accelerator pump by moving the pump drive cam on the throttle control lever of the 1st chamber.
2nd Chamber Throttle Lever Adjustment
Remove carburetor.
Set the throttle valves of both chambers to the idle position of a warm engine: the air damper should be open and the throttle valves should be closed.
Measure the free play of the throttle control lever of the 2nd chamber on the fork of its drive, which should be within 1.00±0.20 mm in the closing direction and 1.20±0.20 mm in the opening direction. If necessary, adjust the free travel of the lever by bending the edges of the fork.
Install carburetor and adjust engine idle.
Warm engine idle adjustment
Idle speed adjustment must be carried out on a warm engine (with fully open air damper) with correctly set ignition timing and adjusted clearances in the valve drive mechanism.
Connect the tachometer and gas analyzer according to the operating instructions.
Set the engine crankshaft speed in the range of 900-1000 rpm with the adjusting screw for the amount of the mixture.
Adjusting screw quality (composition) mixes set carbon monoxide content (SO) in exhaust gases within 0.5-1.5%.
Check and, if necessary, restore the crankshaft speed, then the CO content, repeating these operations until the desired values of both parameters are obtained simultaneously.
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