Adjusting the fuel level in the float chambers
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 air damper by pressing the throttle valve opening cam (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 within 3350-3450 rpm.
If necessary, adjust the starting clearance of the throttle valve of the 1st chamber with a restrictive screw resting on the profiled cam of the slightly opening throttle valve.
The starting clearance must be within 0.65±0.052 mm.
Air damper starting gap adjustment
Remove starter cover.
Fully open the throttle valve by setting the cam slightly open and the throttle valve to the corresponding 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 will decrease 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 clearance 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 gap of the second stage of the air damper, which should be within 3.9±0.15 mm.
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 position of the throttle valve of the 1st chamber is adjusted at the factory, however, if the adjustment is violated, 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 ¼ 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.
Adjusting the throttle opening 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 rod of the drbs-selion pneumatic actuator of the damper of the 1st chamber and turn the cam of the opening of the throttle of the 1st chamber so as to release the throttle 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 in 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 must be open and the throttle valves closed.
Measure the free travel 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.
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