After having properly installed the carburetor on the motor, turn both the high and low speed adjusting screws, A and B, completely down clockwise so that the needle valves just touch their respective seats. Then unscrew (anti-clockwise) the high speed adjusting screw A about three turns off the seat, and turn the low speed adjusting screw B anti-clockwise about one and one-half turns off the seat. These settings are not to be considered as final adjustments of the carburetor. They are merely to be taken as starting points because the motor will run freely with these settings.
After the motor has been started, permit it to run long enough to become thoroughly warm then make the high speed adjustment. Advance the spark to the position for normal running. Advance the gas throttle until the motor is running at approximately 750 r. p. m. Then turn down on the high speed screw A gradually notch by notch until a slowing down of the motor is observed. Then turn up or open the screw anti-clockwise until the motor runs at the highest rate of speed for that particular setting of the throttle.
To make the low speed adjustment B proceed as follows: Retard the spark fully and close the throttle as far as possible without causing the motor to come to a stop. If upon idling the motor tends to roll or load it is an indication that the mixture is too rich and therefore the low speed screw B should be turned away from the seat anti-clockwise, thereby permitting more air to enter into the idling mixture. It is safe to say that the best idling results will be obtained when the screw B is not much more or less than one and one-half turns off the seat.
After satisfactory adjustments have been made with the motor vehicle stationary, it is most important and advisable to take the vehicle out on the road for further observation and finer adjustments. If upon rather sudden opening of the throttle the motor backfires, it is an indication that the high speed mixture is too lean, and in this case the high speed screw A should be opened one notch at a time until the tendency to backfire ceases. On the other hand if when running along with throttle open, the motor rolls or loads, it is an indication that the mixture is too rich, and this condition is overcome by turning the high speed screw A down (clockwise) until this loading is eliminated.
STROMBERG MODEL L CARBURETOR
There are three adjustments; the high speed, the extremely low speed or idle, and the “economizer.”
The high speed is controlled by the knurled nut “A” which locates the position of the needle “E” past whose point is taken all the gasoline at all speeds. Turning nut “A” to the right (clockwise) raises the needle “E” and gives more gasoline, to the left, or anticlockwise, less.
Fig. 33. Stromberg Model “L”—Adjustment Points
If an entirely new adjustment is necessary, use the following practice. Put economizer “L” in the 5th notch (or farthest from float chamber) as an indicator, turn nut “A” to the left, anticlockwise, until needle “E” reaches its seat, as shown by nut “A” not moving when throttle is opened and closed. When needle “E” is in its seat it can be felt to stick slightly when nut “A” is lifted with the fingers. Find adjustment of “A” where it just begins to move with the throttle opening, then give 24 notches to the right or clockwise (the notches can be felt). Then move the economizer pointer “L” back to the 0 notch (toward float chamber). This will give a rich adjustment. After starting and warming up the motor, thin out the mixture by turning “A” anticlockwise, and find the point where the motor responds best to quick opening of the throttle, and shows the best power.