21
Fuel Bowl And Bowl Nut
Whenever a carburetor bowl is removed for service,
the fuel bowl O ring (or gasket on Series "7") and
the bowl nut washer must be replaced. For easier
installation, lubricate the O ring with a small amount
oil.
Installing the Float Bowl
Install the float bowl by placing the detent portion
opposite of the hinge pin. Make sure the deepest
end of the bowl is opposite of the inlet needle. The
bowl has a small dimple located in the deepest part.
The purpose of this dimple is to minimize the chances
of the float sticking to the bottom of the bowl caused
by stale fuel.
Impulse Fuel Pump
The diaphragms must be installed against the center
body with the gaskets against the outside covers. The
parts are designed so they cannot be misassembled
without damage (diag. 57).
To test the unit, assemble the carburetor to the engine,
leaving the fuel line from the pump off. Use a different
fuel tank remotely placed above the carburetor to
provide gravity fuel flow to the carburetor inlet to run
the engine while testing the pump. Make sure fuel is
available in both fuel tanks and the original fuel tank's
fuel line is connected to the fuel pump inlet. Place the
pump outlet line in a proper draining receptacle. With
the pulse line connected from the engine crankcase
to the pump and the engine running, a definite fuel
flow should result at the pump outlet.
If the flow is erratic or intermittent, the pump needs
repair or replacement.
Primer Bulb
To install, start the retainer and bulb into the casting
with the retainer tabs pointed out. Firmly push the
bulb and retainer into position using a 3/4' (19.05 mm)
deep well socket (diag. 58).
Final Checks
Before reinstalling a newly overhauled carburetor, pre-
set the main mixture adjustment screw, the idle
mixture adjustment screw and the idle speed
adjustment screw. See Pre-sets and Adjustments
in this chapter.
56
58
57
VALVE OPEN
VALVE CLOSED
FUEL SUPPLY
PULSE LINE
TO CRANKCASE
VALVE OPEN
CARBURETOR
FITTING
DIAPHRAGM
FILTER
AIR BLEED
ATMOSPHERIC
VENT
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
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DETENT
