Subaru ER12 - 11-4 Diaphragm Type Carburetor

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11-4 DIAPHRAGM TYPE CARBURETOR
11-4-1 OPERATION AND CONSTRUCTION
1. ENGINE IMPULSE
The alternating action of the positive pressure and negative pressure inside the engine crankcase
operates the fuel pump diaphragm
2. FUEL PUMP DIAPHRAGM
The fuel pump diaphragm undulates in response to the engine impulse and as a result of that movement
it feeds the fuel through the fuel pump valve
3. FUEL INLET
The fuel inlet is the opening through which fuel is sucked from the fuel tank
4. INLET VALVE
The inlet valve opens when the diaphragm is submitted to the action of a negative pressure in response
to the movement of the pump diaphragm and the inlet valve shuts when it is submitted to a positive
pressure
5. OUTLET VALVE
Oppositely to the inlet valve, the outlet valve shuts when it is submitted to the action of a negative
pressure and opens when submitted to a positive pressure

6. INLET SCREEN
The inlet screen filters the fuel that is sucked from the fuel tank to the carburetor
7. INLET NEEDLE VALVE
The inlet needle valve controls the fuel that is fed from the fuel pump to the metering chamber
8. THROTTLE VALVE
The throttle valve controls the volume of air sucked into the engine, thereby changing the engine speed
9. AIR VENT HOLE
The air vent hole is open to the atmosphere, with the purpose of allowing smooth operation of the
metering diaphragm