Checking and adjusting the Zenith 2B2 carburetor (Audi 80 B2)

Checking 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±0.5 mm, for the 2nd chamber - 30±0.5 mm. If it does not correspond to this, set the required size by bending the tongues of the float levers.

Adjusting the opening of the throttle valve of the 1st chamber

The position of the limiting screw for opening the throttle valve of the 1st chamber is adjusted during assembly and cannot be changed. If the position of the screw is accidentally disturbed, it can be restored as follows:

• unscrew screw 1 (see photo) so that it moves away from the shaped sector;
• carefully tighten the screw until it touches the sector;
• turn the screw another ¼ turn;
• adjust engine idle speed.

Checking and adjusting the starting gap of the 1st stage of the air damper

Remove the starter cover.

Close the air damper.

Push the movable rod of the air damper pneumatic drive until it stops.

By lightly pressing from top to bottom, select the gaps in the system of levers and rods.

In this position, using a rod or the tail of a thin drill, measure the starting gap of the first stage of the air damper, which should be within 3.15±0.15 mm.

If necessary, adjust the nominal starting clearance using the adjusting screw of the air damper pneumatic drive diaphragm (see photo) and lock the adjusting screw.

Adjusting the starting gap of the 1st stage of the throttle valve

Disconnect the negative cable from the battery.



Remove the carburetor from the engine.

Close the air damper.

Using a rod or the shank of a thin drill, measure the starting clearance of the first stage of the throttle valve, which should be within 0.65±0.05 mm.

If necessary, adjust the gap by turning the adjusting screw "b" (see photo), then adjust the engine idle speed.

Adjusting the automatic starting device

There are marks on the carburetor body and the starting device body that, when the starting device is correctly positioned, should be aligned, as shown in the circle in the photo.

Checking the performance of the accelerator pump

Disconnect the wire from the negative terminal of the battery.

Remove the carburetor.

Place a measuring cup with a funnel under the carburetor.

Open the throttle valve quickly and fully ten times and measure the amount of fuel flowing out into the measuring cup, which should be within 13±1.5 cm³.

To adjust, turn the adjusting nut 2 (see photo) in the direction of the "+" sign to increase the pump performance, and in the direction of the "-" sign to decrease it.



After installing the carburetor, adjust the engine idle speed.

Adjusting engine idle speed

Adjustment of the engine idle speed is performed ON a warmed-up engine (oil temperature not less than 60°C), with the air damper fully open, with the ignition timing correctly set and the clearances in the valve drive mechanism adjusted.

Using a connected tachometer, check the engine crankshaft speed, which should be within 900-1000 rpm.

If necessary, use the mixture quantity adjusting screw (see photo) to achieve the crankshaft rotation speed within the specified limits.



Connect the gas analyzer in accordance with the operating instructions.

Turn off power consumers.

Disconnect the air supply hose from the air filter on the cylinder head cover and close the hose opening with a plug on the air filter side.

Remove the plug from the mixture quality (composition) adjustment screw.

Adjust the CO content in the exhaust gases within 1.0-2.0% by turning the adjusting screw (shown by the arrow in the photo); during adjustment, the radiator cooling fan should not rotate.

After adjustment, lock the adjusting screw and close it with a plug.









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