(12) Check ignition to battery wiring connections (diagram [fig. 48]).
(13) See that battery is not entirely discharged by turning on lights (tactical situation permitting) and observing brilliancy.
b. A carburetor, once correctly adjusted, should require little, if any, readjusting. At most, it should not be necessary to adjust the low speed needle more than one or two notches either way to correct mixture to meet changes in weather conditions.
c. Low Speed Adjusting Needle (figs. [43] and [44]). Adjustment of this needle valve controls only idling and low speed (up to approximately 30 mph) fuel mixture. Turn needle valve down (to right) to make mixture leaner. Back out (to left) needle valve to make mixture richer. Needle valve is held in any desired position by a spring‐and‐ball plunger which engages notches in the needle adjusting screw.
d. Complete Readjustment of Carburetor. A carburetor that is badly out of adjustment, and/or a new carburetor just installed, must be adjusted as follows:
(1) Turn the low speed needle valve all the way down (to right).
(2) Back needle valve out (to left) about three full turns. With needle valve in this position, engine will start, but mixture will probably be too rich.
(3) Start engine as follows: After choke lever has been moved to normal open running position and engine is normally hot, correct adjustment of needle valve by turning needle valve down (to right) one notch at a time until mixture becomes so lean that engine misses, and is inclined to stop: then back out (to left) needle valve 5 to 10 notches, or until engine fires regularly with spark advanced and throttle closed (or as nearly closed as it can be set and still have engine running at idling speed).
(4) Adjust throttle lever stop screw ([fig. 43]) as necessary to make engine idle at proper speed with throttle in fully closed position. Turning stop screw to the right makes engine idle faster. Turning stop screw to the left makes engine idle slower. Do not idle engine at the slowest possible speed, because an extremely slow idling adjustment causes hard engine starting. Changing idling speed with throttle stop screw is likely to change the low speed fuel mixture to some extent: therefore, it will be necessary to again check and correct the low speed needle valve adjustment (step (3) above).