end of tool. Withdraw tool and weight assembly through
(5) Tighten two screws to secure contact
hole in shaft.
(4) Thread counterweight (37) onto valve body
r. Adjust breaker arm spring tension as follows.
(38) while holding tool stationary.
(1) Hook end of spring tension scale calibrated
(5) Tighten counterweight to 50-60 in pounds
in ounces in end of breaker arm contact and pull in
and bend tabs of lock plate (36) again counterweight.
direction perpendicular to plane of contact surfaces. If
Turn tool clockwise gently to bottom adjusting screw.
tension is more or less than specified, loosen both
After bottoming the screw turn tool counterclockwise
breaker arm spring nuts and shift spring on breaker arm
stud to get correct tension.
(6) Install plug (35).
(2) Tighten nuts and recheck tension.
o. Install governor band (34) and secure with a
s. Adjust spark advance as follows.
(1) Mount distributor in a distributor test fixture
p. Aline the points as follows.
and set machine to drive distributor at 1500-2000 rpm.
(1) Rotate cam so points are closed. The
(2) Check the flashes of the rotating disc to see
that they occur at 45 degrees intervals. A variation of
points must touch through circle around hole grounded
one degree indicates a bent distributor shaft or a worn
(2) If contact point is not centered, use needle
bushing or cam. Check and replace these parts.
nose pliers over uprights position of grounded point
(3) Using a screwdriver adjust the primary
bracket and bend bracket slightly in or out, or twist it,
spring (29, fig. 12-1) by bending the primary spring post
until contact surfaces touch at center.
q. Adjust the gap as follows.
away from the shaft decreases advance; bending post
(1) Place distributor in a vise collet and the
toward shaft increases advance). Check and correct
collet in a vise.
adjustment at several points throughout the advance.
(2) Loosen screws holding contact bracket
t. Attach the clamp (1) to housing and secure with
pin (3). Position cap (2) on housing and secure with
(3) Rotate cam until rubbing block is highest
point of cam lobe. Insert a screwdriver between notch in
u. Install distributor on engine as instructed in TM
contact bracket and matching notch in upper plate.
(4) Rotate screwdriver to get proper gap.
Section IV. REPAIR OF CARBURETOR
The carburetor is a four barrel concentric down-draft type
unit. It differs from other carburetors in that it has two
additional or secondary barrels which operate only during
a. Mount carburetor in a holding fixture and secure
periods of heavy engine loads. Throttle plates in the
fixture in vise.
secondary barrel are vacuum operated. The carburetor
b. Remove screw (1), lockwasher (2) and screen
is similar to the dual concentric type carburetor in that it
has two primary barrels each of which contain a venturi,
main fuel discharge nozzle, throttle plate, idle passages
and gasket (7). Remove screw (8) and diaphragm (9).
and choke plate. A throttle operated accelerator pump
d. Remove screw (10) and tube (11).
e. Use a large screwdriver and remove plug (12)
power enrichment system which automatically comes
and gasket (13). Remove valve seat (14) and gasket
into effect whenever an added amount of fuel is needed
(15) in the same manner.
for full power operation. The governor assembly used is
f. Remove screw (16), clamp (17) and tubes (18).
integral with the carburetor and is also vacuum operated
g. Remove secondary jet tubes (19) and gaskets
h. Remove float shaft (21), float (22) and float
Refer to TM 5-3810-294-20 for instructions to disconnect
the fuel lines, controls, linkages, and removal of the
i. Remove valve (24) and gasket (25).
carburetor from the engine.