19
43
RIM
Carb. tool # 670377
41
Diaphragm Carburetors
1. Remove the screws holding the diaphragm cover on.
2. Remove the cover, gaskets, and diaphragm noting or
marking the sequence or location to aid in reassembly.
NOTE: If a "F" designation on the choke end of the
carburetor is present, place the diaphragm on first, then
the gasket and cover. If no "F" is present, the gasket
goes first.
3. Note or mark the high and low mixture adjustment
screws. Remove the screw assemblies.
4. Note or mark the action of the choke and throttle
shutters and the hook points of the choke or throttle
return spring or seal retainer springs located on the top
of the choke or throttle shaft. Remove the throttle
shutter, throttle shaft, choke shutter, springs and choke
shaft by removing the screw or screws that attach the
throttle or choke shutter to the shaft inside the air horn.
5. Use a 9/32" (7.144 mm) thin wall socket to unscrew
and remove the inlet needle and seat assembly (diag.
40).
6. Note and mark the direction of the inlet fitting. If
necessary the inlet fitting can be removed by pulling
with a pliers or vise. Some diaphragm carburetors have
a strainer as an integral part of the fuel fitting. If the
strainer is lacquered or cannot be cleaned, the fitting
must be replaced.
7. Remove all welch plugs if cleaning the carburetor.
Secure the carburetor in a vise equipped with protective
jaws. Use a small chisel sharpened to a
1/8" (3.175 mm) wide wedge point. Drive the chisel
into the plug to pierce the metal, then push down on
the chisel to pry the plug out of the hole.
NOTE: DO NOT REMOVE ANY BALL OR CUP PLUGS.
IMPULSE FUEL PUMP
To service, disassemble the pump by removing the four (4)
screws. Clean all parts with a solvent and install a new kit
which consists of a coil spring, gaskets and diaphragms
(diag. 41 & 42).
FLOAT ADJUSTING PROCEDURE
All Tecumseh carburetors with an adjustable float require
a specific float height adjustment to achieve proper
operation and easy engine starts. To check the float height,
hold the carburetor in an upside down position. Remove
the bowl nut, float bowl, and "O" ring. Place the Tecumseh
carburetor tool #670377 with flat dimensions of 11/64" (4.36
mm) across the top of the carburetor casting on the opposite
side and parallel to the float hinge pin (diag. 43). The float
must just touch the carb tool. If the float is too high or too
low, adjust the height by bending the float tab accordingly.
If the required adjustment is minor, the tab adjustments
may be made without removing the float and carefully
inserting a small bladed screwdriver to bend the tab.
Float sticking can occur due to fuel deposits or when the
fuel tank is filled for the first time, this condition can be
quickly corrected by loosening the carburetor bowl nut one
full turn. Turn the bowl 1/4 turn in either direction, then
return the bowl to its original position and tighten the bowl
nut.
"F"
DIAPHRAGM FIRST NOT GASKET
40
"F" DESIGNATION
42
OLD STYLE
NEW STYLE
CRANKCASE PRESSURE
ATMOSPHERIC PRESSURE ACTING ON
DAMPING DIAPHRAGM
FUEL FLOW
CRANKCASE SUCTION AND
FLOW DIRECTION
ATMOSPHERIC PRESSURE
ACTING ON DAMPING
DIAPHRAGM
SUCTION FUEL FLOW DIRECTION
ATMOSPHERIC PRESSURE CAUSED
FUEL FLOW
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VALVE CLOSED
ATMOSPHERIC
VENT
CARBURETOR
FITTING
VALVE OPEN
DIAPHRAGM
FILTER
PULSE LINE
TO CRANKCASE
VALVE
CLOSED
AIR BLEED
FUEL SUPPLY
VALVE OPEN
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