4.12. Cleaning and adjustment of the carburetor

In this section the procedure for the carburetor 2B4 is described. The procedure for the carburetor 2 - is similar.



  1. Acquire a full set of laying and epiploons for the carburetor.
  2. Wash up the external surfaces of the carburetor.
  1. By means of the screw-driver unhook draft of the accelerating pump from the lever of a throttle of primary camera (it is shown by an arrow).
  1. Turn off bolts of fastening of a cover to the main case. The otvorachivaniye of the central bolt will require a prutkovy key.
  1. Unhook draft from the plastic lever of the air gate (it is shown by an arrow).
  1. Disconnect a cover from the main case and remove laying.
View of a cover from within.
View of the carburetor without cover.
  1. Unscrew the screw of fastening of an arm of the drive of a throttle to the throttle case. (it is shown by an arrow).
  1. Disconnect a rod of the vacuum drive from the lever of a throttle of the secondary camera.
  1. Unscrew screws of fastening of the case of a throttle to the main case.
  1. Unhook intermediate draft of a throttle. If it is difficult, then turn off a nut and disconnect the lever from an axis of a throttle of primary camera, having taken measures not to damage a returnable spring.
  1. Disconnect the case of a throttle from the main case and remove laying.

The bottom view without throttle case - pay attention to laying to the main case:

  1. Having turned a cover, push out axes of floats, remove floats...

... also take needle valves - keep them according to an arrangement.

  1. Turn out a fuel jet of direct giving from the secondary float-operated camera.

... then similarly turn out jets from a cover - keep them according to an arrangement.

Secondary main jet (1) and fuel jet of TM (thermo-starter) (2).
Secondary main jet (at the left) and a fuel jet of TM (on the right), wrapped in a cover.
Secondary air jet of direct giving (1), air jet of TM (2) and the correcting air jet (3).
The provision of jets in a cover (are shown by shooters).
  1. Clear all components and blow air of low pressure internal channels.
  2. Assembly back to dismantling, however, pay attention to the next moments:
    • Establish new laying and epiploons from repair set.
    • Before installation of a cover, check that draft of the air gate was correctly connected to the lever.
    • Check and if necessary adjust installations of floats. Turn a cover and check distance from the interfaced surface (without laying) to float top, having convinced that the sprung ball of the needle valve is not pressed. Pay attention that this distance not identical to primary and secondary floats (watch the Size table and adjusting data at the end of the Management). If adjustment is required, then bend the float lever as it is required.
    • Make sure that in the top part of the accelerating pump the epiploon is established.


Adjustments of turns of idling and quality of mix are stated in the Head Routine maintenance of the car.

Automatic air gate (2B4)


  1. Check that tags of combination of the case and a cover of the automatic air gate are well distinguishable; if is not present, put new tags.
  1. Unscrew three screws and take a metal ring.
  1. Remove a plastic ring, at the same time disconnecting a bimetallic spring from a control lever.
  1. Fasten the rubber film (2) to the lower part of a control lever. Press the lever to the right and a drill with a diameter of 4.2 mm (1) check distance between bottom edge of the air gate and a wall of the carburetor. For movement of the lever periodically influence the vacuum drive discharge.
  1. If adjustment is necessary, rotate it is shown by an arrow) on the end of the vacuum drive.
  1. Upside-down establish a cover, having convinced that tags are combined.

Drive of a throttle (2B4)


  1. At being in the provision of idling a throttle check that length of a spring made 23.0 ±1.0 mm. If differently, adjust a nut.
  2. When discharge is absent (the engine does not work), check that the lever course measured between the lock screw and the lever made 5.0 ±0.5 mm. If necessary weaken a lock nut and rotate a diaphragm rod. After adjustment tighten a lock nut.

Throttle drive (2)

For difficult adjustment of the carburetor 2 special tools are required. Therefore such work should be charged to the dealer of BMW.