Figure 4-5. Carburetor adjustments.

(2) Adjust the main adjusting screw (fig. 4-5).

(c) T u r n t h e a d j u s t i n g s c r e w c o u n -

This adjustment determines the amount of fuel

terclockwise until the engine runs smoothly without

available for high-speed operation. Adjust as

missing.

follows:

(3) Adjust the idle mixture adjustment screw

(fig. 4-5). This adjustment controls the amount of

air admitted to the idling system which functions

only at low speeds. You should adjust as follows:

(a) With the engine at idle, turn the idle

mixture adjustment screw counterclockwise to cut

off air, making the fuel mixture richer until the

engine starts to run roughly due to excessively rich

mixture.

(b) Turn the adjustment screw clockwise to

obtain the smoothest idle operation possible.

on the control panel, you can adjust the screw for

the highest engine vacuum.

(4) Adjust the idle speed adjustment screw

(fig. 4-5). Turn the screw clockwise or coun-

terclockwise as necessary to provide 1400 50 rpm

idle speed when the pump throttle control is set to

idle.

b. Removal.

NOTE

Remove carburetor only if troubleshooting indicates

Figure 4-5. Carburetor adjustments.

faulty operation requiring replacement.

(a) Adjust the throttle control of the pump

(1) Disconnect the carburetor throttle lever

to set the carburetor throttle at about one-fourth

from the governor control rod linkage. Refer to

open.

(b) Turn the main adjusting screw clock-

wise to reduce the fuel to the engine until~the engine

begins to miss due to a lean fuel mixture.

Figure 4-6. Governor and carburetor linkage.