This article describes the procedure for carburetor 2B4. The procedure for the carburetor 2BE is similar.
Carburettor Cleaning 2B4, 2BE
1. Obtain a complete set of gaskets and seals for the carburettor.
2. Wash the outer surfaces of the carburetor.
3. Using a screwdriver, detach the thrust of the accelerator pump from the primary choke lever of the primary chamber (indicated by an arrow).
4. Remove the bolts securing the cover to the main body. To unscrew the central bolt, you need a rod key.
5. Unhook the rod from the plastic lever of the air damper (shown by the arrow).
6. Remove the cover from the main body and remove the gasket.
View of the lid from the inside.
A view of the carburettor without a cover.
7. Unscrew the screw of fastening of an arm of a drive of a throttle to the case of a throttle. (shown by an arrow).
8. Disconnect the vacuum actuator stem from the throttle lever of the secondary chamber.
9. Remove the throttle body mounting screws to the main body.
10. Unhook the intermediate throttle rod. If this proves difficult, then unscrew the nut and disconnect the lever from the throttle axis of the primary chamber, taking care not to damage the return spring.
11. Disconnect the throttle body from the main body and remove the gasket.
Bottom view of the main body without throttle body – pay attention to the gasket:
12. Turn the cover over, push out the axes of the floats, remove the floats …
… and remove the needle valves – keep them in accordance with the location.
13. Remove the fuel injector from the secondary float chamber.
… then in the same way turn the nozzles out of the lid – keep them in accordance with the location.
Secondary main jet (1) and fuel jet TM (thermo-starter) (2).
Secondary main jet (left) and fuel jet TM (right), wrapped in a lid.
Secondary air jet of direct feed (1), air jet TM (2) and correcting air jet (3).
Position of the nozzles in the lid (shown by arrows).
14. Clean all components and purge the internal channels with low-pressure air.
15. Assembling the reverse of the disassembly, however, pay attention to the following points:
– Install new gaskets and seals from the repair kit.
– Before installing the cover, check that the air damper draft is correctly connected to the lever.
– Check and, if necessary, adjust the float settings. Turn the cover over and check the distance from the mating surface (without gasket) to the top of the float, making sure that the spring-loaded ball of the needle valve is not pressed. Note that this distance is not the same for the primary and secondary floats. If adjustment is required, then bend the float lever as required.
– Make sure that an oil seal is installed at the top of the accelerator pump.
Adjusting the carburetor 2B4, 2BE
Automatic air damper (2B4)
1. Check that the alignment marks of the body and the cover of the automatic choke are clearly distinguishable; if not, apply new labels.
2. Remove the three screws and remove the metal ring.
3. Remove the plastic ring while disconnecting the bi-metal spring from the control lever.
4. Attach the rubber band (2) to the lower part of the control lever. Push the lever to the right and a 4.2 mm diameter drill (1) check the distance between the lower edge of the choke and the carburettor wall. To move the lever, periodically apply pressure to the vacuum actuator.
5. If adjustment is required, rotate by arrow) on the end of the vacuum actuator.
6. Reinstall the cover in the reverse order, making sure the tags are aligned.
Throttle actuator (2B4)
1. With the throttle in idling position, check that the spring length is 23.0 ± 1.0 mm. If not, adjust the nut.
2. When there is no discharge (the engine does not work), check that the lever travel, measured between the locking screw and the lever, is 5.0 ± 0.5 mm. If necessary, loosen the lock nut and rotate the diaphragm rod. After adjustment, tighten the lock nut.
Throttle Drive (2EV)
For complex adjustment of carburetor 2BE special tools are required. Therefore, such work should be entrusted to a BMW dealer.