Carburetor - Nikki 2-bbl Mazda 626 GC

DESCRIPTION

Carburetor is a 2-barrel downdraft type. It is equipped with an electric automatic choke, coasting richer system, air vent solenoid, slow fuel cut solenoid, and computer controlled air/fuel (A/F) solenoid. A double venturi provides for high air flow velocity at the venturi under all operating conditions, resulting in more efficient atomization of fuel for smooth combustion.

ADJUSTMENTS

Note. For all on-vehicle adjustments not covered in this article. See the appropriate TUNE-UP article.

FLOAT LEVEL

Remove air horn from carburetor. Invert air horn and allow float to hang by its own weight. Measure clearance between float and air horn gasket surface, with gasket removed. If clearance is not.53" (13.5 mm), bend float seat to adjust. (Scheme 26)

Float Level Adjustment Bend float seat to adjust. Scheme 26

FLOAT DROP

Turn air horn upright and allow float to hang by its own weight. (Scheme 27) Measure distance between bottom of float and air horn. If distance is not 1.93" (49 mm), bend float stop to adjust.

Float Drop Adjustment Bend float stop to adjust. Scheme 27

CHOKE LINKAGE (FAST IDLE OPENING ANGLE)

Fully close choke valve. Position fast idle lever on second step of fast idle cam. Measure clearance between throttle valve and wall of throttle bore. Clearance should be.028-.043" (.70-1.1 mm). Adjust by turning fast idle adjustment screw. (Scheme 28)

Choke Linkage Adjustment (Fast Idle Opening Angle) Turn fast idle adjustment screw to adjust. Scheme 28

CHOKE VALVE OPENING

1. Check choke linkage adjustment, then place fast idle lever on second step of fast idle cam. Measure clearance between choke valve and air horn.
2. Choke valve clearance should be.023-.039" (.60-1.00 mm). Adjust clearance by bending starting arm. If large adjustment is necessary, bend choke rod. (Scheme 29)

Choke Valve Opening Adjustment Bend starting arm for small adjustment, choke rod if large adjustment is necessary. Scheme 29

CHOKE DIAPHRAGM

1. Apply approximately 15.7 in. Hg vacuum to choke diaphragm vacuum tube. Fast idle lever should be on first (high) step of cam.
2. Gently press choke valve closed and measure clearance between upper edge of choke valve and air horn. Bend choke lever tab until clearance is.067-.087" (1.70-2.20 mm). (Scheme 30)

Choke Diaphragm Adjustment Bend choke lever tab to adjust. Scheme 30

CHOKE UNLOADER

Fully close choke valve, open primary throttle valve completely and measure clearance between upper edge of choke valve and air horn. Adjust clearance to.112-.144" (2.85-3.65 mm) by bending unloader tab. (Scheme 31)

Choke Unloader Adjustment Bend unloader tab to adjust. Scheme 31

SECONDARY THROTTLE VALVE OPENING ANGLE

1. Secondary throttle valve should begin to open when primary throttle valve opens 48-52° and should be fully open when primary valve is fully open.
2. Check clearance of primary throttle valve and wall of throttle bore as secondary throttle valve begins to open. Bend throttle arm tab until clearance is.244-.283" (6.2-7.2 mm). (Scheme 32)

Secondary Throttle Valve Opening Adjustment Bend throttle arm tab to adjust. Scheme 32

ACCELERATOR LINKAGE

1. Accelerator pedal cable free play at carburetor should be.04-.12" (1-3 mm). If free play is not to specifications, adjust cable adjusting nut.
2. To check pedal height, depress pedal to the floor and check that throttle valves are wide open. If necessary, adjust stop bolt. (Scheme 33)

Accelerator Pedal Height Adjustment Turn adjusting nut to adjust cable; stop bolt to adjust pedal height. Scheme 33

Scheme 34

1. Remove vacuum break vacuum hose, accelerator pump connecting rod and lever and throttle return spring. Unplug the air vent solenoid valve wire connector.
2. Disconnect choke rod and separate air horn and automatic choke assembly from carburetor body. Remove air vent solenoid and gasket. Remove float, pin and gasket.
3. Remove needle valve assembly. Remove coasting richer solenoid valve and idle switch. Remove fuel cut solenoid valve and gasket. Remove dash pot bracket and dash pot.
4. Remove accelerator pump plunger assembly and spring. Remove retaining clip and check valve plug. Invert body, remove strainer and accelerator pump inlet check ball.
5. Remove accelerator pump outlet check ball and spring. Disconnect throttle link, vacuum diaphragm connecting rod and separate throttle body from main body. NOTE: One of the bolts attaching main body is in throttle body between throttle valves.
6. Remove diaphragm cover mounting screws, gasket, cover, spring and diaphragm. Remove throttle lever hanger mounting screws. Remove fuel bowl sight glass mounting screws.
7. Remove cover, gasket, glass and rubber gasket. Remove all air bleeds and jets from main body. Note size and position of all jets and bleeds for installation in original position. (Scheme 34) (Scheme 34): Air Bleed and Jet Removal
8. Remove throttle hanger and other levers, but do not remove throttle valve and shaft, venturi or choke valve and shaft from throttle body. When removing mixture adjusting screw, press out the spring pin (Scheme 35)

Throttle Body Assembly. Scheme 35

CLEANING & INSPECTION

1. Wash all parts in clean gasoline and blow out fuel passages with compressed air. Never use wire for cleaning jets. Inspect air horn, main body and throttle body for cracks and breakage.
2. Check float needle and seat for wear and float for damage. Inspect choke shaft and throttle shaft for wear. Examine all jets and air bleeds for clogs. Inspect accelerator pump plunger for wear or damage.
3. Check diaphragms and inspect mixture adjusting screws. Test solenoid valve operation by grounding body while touching terminal to battery positive post. Valve stem should pull into solenoid body.
4. Check for continuity between choke heater coupler and ground with ohmmeter. If there is no continuity, replace heater. Connect one A/F solenoid valve lead wire to positive terminal of battery, other to ground.
5. Blow air through valve to ensure it is working properly. When current is applied, air should not pass through valve. When current is not applied, air should pass through valve.

REASSEMBLY

To reassemble, reverse disassembly procedure, being careful not to mistake primary and secondary parts. Do not secure the spring pin to lock the mixture adjusting screw until idle adjustment has been completed.

ADJUSTMENT SPECIFICATION

CARBURETOR ADJUSTMENT SPECIFICATIONS