(from Weber General Catalog 1/5/1961)

    The fuel arrives through the needle valve (1) to the bowl (4) where the float (3) controls the opening of the needle (2) in order to maintain a constant fuel level. Through the ducts (6) and the main jets (5), it reaches the emulsioning tubes (12) from which after having been mixed with the air coming  from the air corrector jets (11), through the pipes (10) and the nozzles (7) it reaches the carburation area consisting of the auxiliary Venturi's (8) and chokes (9).

    The fuel flowing from the bowl (4) arrives to the starting device through the ducts (32) and the starting jets (30). Emulsified with the air coming from the hole (29) it reaches the valves opening (35) through the ducts (31) and definitely emulsified by the air entering from orifices (34) is then carried by means of the ducts (33) to the carburetor throats below the throttles.
    Engine cold starts: starting device inserted (position A)

    Engine starts half warm: partial insertion of the device (position B)

    Engine warm ups: during engine warming up, even if the vehicle is under way, the starting device must be gradually pushed into the rest position.

    Normal operation: starting device must be pushed back as soon as the engine has reached the operating temperature (position C)


 Idling Operation and Progressive Action

The fuel is carried from the bowl (4) to the calibrated holes of the idling jets (14) through the ducts (15). Emulsified with the air coming from the ducts (13) through the ducts (20) and the idling feed holes (18) adjustable by means of screws (19) the fuel reaches the ducts (20) the mixture can reach the carburetor throats also through the progression holes (16)


By closing the throttle valves, the lever (25) , by means of the shaft (27), lifts the piston (26). the fuel is thus drawn from the bowl (4) into the pump cylinder through the suction valve (23). By opening the throttles, the shaft (27) is free and the piston (26) is pushed down under the action of the spring (28), by means of the ducts (22) the fuel is injected into the carburetor throats. The inlet valve (23) is provided with a calibrated hole which is discharges the excess fuel delivered by the accelerating pump in to the float bowl.



  1. 1  Make sure that the weight of the float is the correct one (26 grams), that the float can freely slide on the axis and does not show any pits.
  2. 2  Make sure that the needle valve (v) is tightly screwed in its housing and that the pin ball (Sf) of the dampening device incorporated in the needle (S) is not jammed.
  3. 3  Keep the carburetor cover (C) in a vertical position as indicated in the above figure, since the weight of the float (G) could lower the pin ball (Sf) fitted on the needle (S)
  4. 4  With carburetor cover (C) in vertical position and float clip (Lc) in light contact with the pin ball (Sf) of the needle (S) the distance of both half-floats from upper surface of carburetor cover (C) with gasket (Gz) in place, must measure 8.5mm.
  5. 5  After the leveling has been done, check that the stroke of the float is 6.5mm. If necessary adjust the position of the lug (A).
  6. 6  In case float (G) had not been rightly set, rectify the position of float clip (Lc) till the required quota is reached, taking care that the clip (Lc) does not show any pit on the contact surface that could affect the free sliding of the needle.
  7. 7  Fit up the carburetor cover making sure that float can move with out any hindrance or friction.
NOTE: the operation of leveling of the float must be carried out whenever it is necessary to replace the float and needle valve: in this case it is advisable to replace also the sealing gasket, making sure that the new needle valve is tightly screwed in its housing.



5. Idle jet holders  7. Idle air orifices  16. Additional Air Horns  18. Pump inlet valve  29.  Idle mixture adjustment screws  30. Pump jets   34. Pump control rod  39 Spring guides and retainers  42. Mixture ducts  43. Starting Jets  45. Starting jet wells  61. Pump deliver vlave  62. Progression holes inspection screw  63. Emulsion tubes complete with main jets and air corrector jets  64. Air Horns mounting plate.  65.  Bowl plate  66. Idle speed adjusting screw  66. Idle speed adjusting screw  67.  Throttle control lever  68. Retainer Washers  69. Pump Spring retainer plate  70. Throttle return spring retaining plate






I highly recommend you buy and use the Weber Service Manual for DCOE carburetors! It gives detailed pictures on how to repair your Weber carbs. If you want to know more about the way Webers work,  you purchase the book on Weber Theory. Try your local book stores or Autobooks in Michigan.


 This web site was created using Weber printed materials and copied verbatim
credit is here by given to E.Weber, Bologna Italy
This page created 4/8/98-revised 4/22/00