Carburetor - Hitachi 2-bbl Subaru Justy I

DESCRIPTION

Carburetor is a 2-barrel downdraft design with primary and secondary throttle system. A choke valve and idle circuit are used in primary system only. Both primary and secondary venturis have main fuel nozzles.

A mechanical accelerator pump and vacuum operated power valve are used for increased fuel requirements. An anti-dieseling switch or solenoid valve is used to stop fuel flow in idle circuit (on some models) when ignition switch is turned off.

Some models use an altitude compensator device to maintain optimum air/fuel ratio at higher altitudes. Some carburetor models may also include dashpots, throttle positioners, vacuum break diaphragms, bowl vent solenoid valves, and other specialized devices.

CARBURETOR IDENTIFICATION

ADJUSTMENTS

Note. For all on-vehicle adjustments not covered in this article, see TUNE-UP article in the TUNE-UP section.

FLOAT LEVEL

Note. If fuel is not within mark on float chamber sight glass, with engine idling, remove air horn and adjust using following procedures.

Invert air horn, let float hang by its own weight and measure distance between float and air horn gasket surface (gasket removed). If necessary, bend tab "A" to adjust. (Scheme 51)

Adjusting Float Level Bend tab "A" to adjust. Courtesy of Nissan Motor Co., U.S.A. Scheme 51

FLOAT DROP

1. After checking float level, gently lift float until float stop contacts air horn projection. Hold float up in this position.
2. Measure clearance between float tab and needle valve. Adjust by bending float stop. (Scheme 52)

Adjusting Float Drop Bend float stop to adjust. Courtesy of Nissan Motor Co., U.S.A. Scheme 52

Bench Adjustment

Close choke valve. Position fast idle lever on 1st (high) step of fast idle cam. Measure clearance between primary throttle valve and wall of throttle chamber. Adjust by turning fast idle adjustment screw. (Scheme 53)

Scheme 53

SECONDARY THROTTLE CLEARANCE

1. Secondary throttle valve begins to open when primary throttle valve opens at 47 degrees on Justy models, 50 degrees on all other models.
2. To check adjustment, measure clearance between primary throttle valve and wall of throttle chamber, as secondary throttle valve begins to open. If adjustment is necessary, bend adjustment tang to obtain specifications. (Scheme 54)
3. Check clearance between primary throttle plate and throttle body. Clearance should be.236" (6.0 mm) on Justy models and.2713" (6.89 mm) on all other models.

Scheme 54

DISASSEMBLY

1. Remove throttle return spring, pump lever shaft, pump lever, spring and spring washer. Disconnect cam connecting rod, cotter pins and washers. Remove return spring on return plate. Unclamp harness at 2 points.
2. Remove anti-dieseling switch. Remove the diaphragm bracket, choke chamber, gaskets and screws. Be careful not to damage the float. Remove secondary diaphragm snap ring, secondary diaphragm, gasket and screws.
3. Separate float chamber and throttle chamber. To disassemble choke chamber, remove accelerator pump piston and pump cover. Remove float shaft, float and needle valve. Remove primary and secondary slow air bleeds.
4. Remove switch vent solenoid valve, gasket and screws. Remove piston return spring, ball and injector weight. Remove primary and secondary main air bleeds. Remove primary and secondary plugs and slow jets.
5. Remove lock plate, float chamber drain plugs and primary and secondary main jets and power valve. Remove throttle adjusting screw and spring and idle adjusting screw and spring. Remove nuts and parts on throttle valve shaft.

CLEANING

Note. Do not immerse synthetic parts, electrical components or diaphragm assemblies in carburetor cleaner.

Replace all parts contained in service overhaul kits. Clean cast parts with carburetor cleaner. Clean jets, fuel passages and vacuum ports with compressed air. Do not use wire or pointed metal objects. Clean all other parts with solvent and soft brush.

INSPECTION

1. Inspect air horn, throttle body and main body for cracks, nicks or burrs on gasket surfaces; float for damage, wear or deformation; needle valve for wear and improper seating and seat strainer for rust or breaks.
2. Inspect jets and air bleeds for clogged orifices, damaged threads, heads slots and installation holes. Check thermostat cover for continuity between wire connector and heater housing. Replace heater if no continuity.
3. Inspect accelerator pump piston assembly for wear on sliding portion and leather cup and check spring for rust. Inspect secondary diaphragm for wear or damage and throttle valves for smooth movement and shaft wear.
4. Check diaphragm assemblies for leaks and proper operation. Apply battery voltage to terminals of solenoid valves and electric switches. Listen for operating sound as terminals are connected and disconnected.

REASSEMBLY

1. To reassemble, reverse the disassembly procedure using all new gaskets, taking care not to mistake primary and secondary barrel parts.
2. Install piston return spring with hook portion facing downward.

Scheme 55

SPECIFICATIONS

CARBURETOR ADJUSTMENT SPECIFICATIONS