Figure 4-29.2. Pump Adjustment

TM 10-3930-633-12

f. Installation. Refer to paragraph 4-58 and

unthread one turn as a preliminary adjusting setting.

Install throttle shaft and plate.

install carburetor. Make final carburetor adjustment

after installation according to instructions in

CAUTION

paragraph 4-57.

Do not force idle mixture adjustment

4-59. Governor

needles against seats, or damage may

result.

a. General. The velocity governor is a single unit

mounted between the carburetor and the intake

(7) Invert main body and place new throttle

manifold. The governor is operated by a combination

body gasket on bowl. Fasten throttle body to bowl

of manifold vacuum and the air flow past the

body with screws and lockwashers; tighten securely.

governor valves. The governor throttle valves are

(8) Install pump discharge valve ball and

offset in the throttle bore so that the combined force

weight into main body. Install pump rod and bracket

of manifold vacuum and the fuel-air flow through the

into bowl cover. Install power valve piston assembly.

bores has greater effect on the larger, upstream area

(9) Install choke lever, choke shaft, and choke

of the valves. This forces the throttle valves to move

plate in the bowl cover. Assemble the accelerator

toward the closed position restricting the fuel-air

pump piston to the pump rod inside the bowl cover.

flow. The closing action of the throttle valves is

Install new main body gasket.

opposed by the control spring. The control spring is

(10) Carefully lower bowl cover down over the

attached to the throttle valve shaft cam. The cam

main body, and check to see that accelerator pump

provides a balance between the closing action of the

plunger is guided properly into the well.

throttle valves and the action of the control spring at

(11) Position choke bracket and dashpot

all engine speeds. Under operating conditions, the

bracket, and secure with bowl cover screws. Install

governor throttle valves do not close, but remain

remainder of bowl cover screws,

open enough to allow the required quantity of the

(12) Install fast idle rod and pump operating

fuel-air mixture to flow into the' manifold to maintain

link, and fast idle screw,

the governed engine speed. To maintain the proper

e. Preliminary Adjustments.

vacuum to the distributor, the governor has two

(1) With throttle lever in the idle position, the

interconnected vacuum transfer ports and a vacuum

distance from the edge of the vacuum passage casting

transfer plunger. When the governor throttle valves

to the center of the hole in the pump operating rod

are forced toward the closed position, vacuum from

should be 27/32 inch as shown in figure 4-29.2. Bend

the lower port is supplied to the distributor to

pump rod to obtain proper dimension.

maintain sufficient spark advance. W h e n the

governor throttle valves are open wide enough, the

plunger shuts off the bottom port and the top port

supplies vacuum to the carburetor distributor vacuum

passage for sufficient vacuum to the distributor.

b. Adjustment. If engine governed speed is too

low or too high, and governor setting is to be checked

and adjusted, proceed as follows:

(1) Connect as tachometer to the engine. With

the engine at normal operating temperature, operate

the engine at wide open throttle and compare the

RPM with the operating range of the governor. The

operating range is stamped on the governor plate (see

figure 4-29).

(2) If governed speed is within range, stop the

engine and remove the tachometer.

(3) If adjustment is required or desired,

remove the governor seal. To increase RPM, turn the

cap counterclockwise. To decrease RPM, turn the

cap clockwise. When adjustment is completed, stop

the engine, seal the cap, and remove the tachometer.

Figure 4-29.2. Pump Adjustment

removal

and

c. Replacement,

Governor

replacement procedures are given in paragraph 4-58.

(2) With dashpot stem depressed and linkage

Governor and related parts are illustrated in figure

set at idle speed, 3/32 clearance should exist between

4-30. Perform governor adjustment after installation

end of dashpot stem and tang on pump operating

of new governor.

rod. See figure 4-29.2.

4-45.1

Change 1