Honda Accord/Civic/Prelude 1973-1983 Repair Guide

Carburetor

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TROUBLESHOOTING



Carburetor problems are among the most difficult internal combustion engine malfunctions to diagnose. The most reliable way for a nonprofessional to diagnose a bad carburetor is to eliminate all other possible sources of the problem. If you suspect the carburetor is the problem, perform the adjustments given in this section. Check the ignition system to ensure that the spark plugs, contact points, and condenser are in good shape and adjusted properly. Check the emission control equipment. Check the ignition timing adjustment. Check all vacuum hoses on the engine for loose connections or splits or breaks. Make sure the carburetor and intake manifold attaching bolts are tightened to the proper torque.

If you do determine that the carburetor is malfunctioning, and the adjustments in this section don't help, you have three alternatives: you can take it to a professional mechanic and let him fix it, you can buy a new or rebuilt carburetor to replace the one now on your vehicle, or you can buy a carburetor rebuilding kit and overhaul your carburetor.

ADJUSTMENTS



Fast Idle

During cold engine starting and the engine warm-up period, a specially enriched fuel mixture is required. If the engine fails to run properly or if the engine over-revs with the choke knob (if so equipped) pulled out in cold weather, the fast idle system should be checked and adjusted. This is accomplished with the carburetor installed.

1973 1170cc AND 1237cc MODELS
  1. Run the engine until it reaches normal operating temperature.
  2.  
  3. With the engine still running, pull the choke knob out to the first detent. The idle speed should rise to 1,500-2,000 rpm.
  4.  
  5. If the idle speed is not within this range, adjust by bending the choke rod. (See Choke Adjustment section below for further details.)
  6.  

1974-79 1170cc AND 1237cc MODELS
  1. Open the primary throttle plate and insert an 0.8mm diameter drill bit between the plate and the bore.
  2.  
  3. With the throttle plate opened 0.8mm, bend the reference tab so it is midway between the two scribed lines on the throttle control lever.
  4.  

1975-79 1487cc AND 1600cc MODELS
  1. Run the engine until it reaches normal operating temperature.
  2.  
  3. Place the choke control knob in its second detent position (two clicks out from the dash). With the choke knob in this position, run the engine for 30 seconds and check that the fast idle speed is 2,500-3,500 rpm.
  4.  
  5. To adjust, bend the slot in the fast idle adjusting link. Narrow the slot to lower the fast idle, and widen the slot to increase. Make all adjustments in small increments.
  6.  

1335cc, 1487cc (1980-83) AND 1751cc MODELS
  1. Run the engine to normal operating temperature.
  2.  
  3. Connect a tachometer according to the manufacturer's specifications.
  4.  
  5. Disconnect and plug the hose from the fast idle unloader.
  6.  
  7. Shut the engine off, hold the choke valve closed, and open and close the throttle to engage the fast idle cam.
  8.  
  9. Start the engine, run it for one minute. Fast idle speed should be 2,300-3,300 rpm (manual transaxle) or 2,200-3,200 rpm (automatic transaxle).
  10.  
  11. Adjust the idle by turning the fast idle screw.
  12.  

1829cc PRELUDE
  1. Start the engine and bring it to normal operating temperature. Turn the engine OFF .
  2.  
  3. Remove the E-clip and flat washer from the thermo-wax valve linkage, then, slide the linkage past the fast idle cam.
  4.  

Be careful not to bend the linkage or the fast idle speed will be changed.

  1. While holding open the throttle, turn the fast idle cam counterclockwise until the fast idle lever is on the 3rd step.
  2.  
  3. Without touching the throttle, start the engine and check the idle speed. The idle speed should be 2,000 rpm. Adjustment of the idle speed can be made by turning the fast idle adjusting screw.
  4.  
  5. Stop the engine and reconnect the thermo-wax valve linkage.
  6.  
  7. Start the engine and check that as the engine warms up, the idle speed decreases.
  8.  

If the idle speed doesn't drop, clean the linkage along with the carburetor. If the speed still doesn't drop, check for damaged or stuck linkage.

Float and Fuel Level

Poor fuel combustion, black sooty exhaust, and fuel overflow are indications of improper float level. Lean running may also be a symptom, although you should also check for such causes as jets blocked by dirt and vacuum leaks.

1170cc AND 1237cc MODELS
  1. Check the float level by looking at the sight glass on the right of the carburetor. Fuel level should align with the dot on the sight glass. If the level is above or below the dot, the carburetor must be disassembled and the float level set.
  2.  

Try to check float level with the dot at eye level.

  1. Remove the carburetor from the engine and disconnect the air horn assembly from the carburetor body.
  2.  
  3. Invert the air horn and raise the float.
  4.  
  5. Now lower the float carefully until the float tang just touches the needle valve stem. The valve stem is spring loaded, so do not allow the float to compress the spring during measurement. Measure the distance between the float and the air horn flange (without gasket). The distance should be 11mm. Adjust by bending the tang.
  6.  
  7. Raise the float until the float stop contacts the air horn body. Measure the distance between the float tang and the needle valve stem. The distance should be 1.3-1.77mm. Adjust by bending the float stop tang.
  8.  
  9. When the carburetor is installed, recheck the float level by looking into the carburetor float sight glass. Fuel level should be within the range of the dot on the glass.
  10.  

1335cc, 1487cc, 1600cc AND 1751cc MODELS THROUGH 1981

See Figures 1, 2 and 3

Due to the rather unconventional manner in which the Keihin 3-bbl carburetor float level is checked and adjusted, this is one job best left to the dealer, or someone with Honda tool No. 07501-6570000 (1487 and 1600cc engines) or 07501-6950100 (1751cc engines); which is a special float level gauge/fuel catch tray/drain bottle assembly not generally available to the public. This carburetor is adjusted while mounted on a running engine. After the auxiliary and the primary/secondary main jet covers are removed, the special float gauge apparatus is installed over the jet apertures. With the engine running, the float level is checked against a red index line on the gauge. If adjustment proves necessary, there are adjusting screws provided for both the auxiliary and the primary/secondary circuits atop the carburetor.



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Fig. Fig. 1: Inspection window showing the fuel level on the 1982 and later models, except 1829cc Prelude



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Fig. Fig. 2: Float level adjustment screw-1982 and later models, except 1829cc Prelude



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Fig. Fig. 3: Float level measurement on the dual Keihin sidedraft carburetors-1829cc Prelude

1982 AND LATER, EXCEPT 1829cc PRELUDE

With the vehicle on level ground and at normal operating temperature, check the primary and secondary fuel level inspection windows. If the fuel level is not touching the dot, adjust it by turning the adjusting screws which are located in recessed bosses above the inspection windows.

Do not turn the adjusting screws more than 1 turn every 15 seconds.

1982 AND LATER 1829cc PRELUDE
  1. Remove the side draft carburetors from the engine and remove the float chambers from the carburetors.
  2.  
  3. Using a float level gauge, measure the float level with the float tip lightly touching the float valve and the float chamber surface tilted about 30° from vertical. The float level should be 16mm.
  4.  
  5. To adjust the float level on the sub carburetor, remove the float chamber. Using a float level gauge, measure the float level as described above.
  6.  

The float level of the sub carburetor cannot be adjusted. If the float level is incorrect the float must be replaced.

Throttle Linkage

See Figures 4 and 5

1170cc AND 1237cc MODELS
  1. Check the gas pedal free-play (the amount of free movement before the throttle cable starts to pull the throttle valve). Adjust the free-play at the throttle cable adjusting nut (near the carburetor) so the pedal has 1.0-3.0mm free-play.
  2.  
  3. Make sure that when the accelerator pedal is fully depressed, the primary and secondary throttle valves are opened fully (contact the stops). If the secondary valve does not open fully, adjust by bending the secondary throttle valve connecting rod.
  4.  



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Fig. Fig. 4: Loosen the throttle cable adjustment retaining nut



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Fig. Fig. 5: Throttle cable adjustment

1335cc, 1487cc, 1600cc AND 1751cc MODELS
  1. Remove the air cleaner assembly to provide access.
  2.  
  3. Check that the cable free-play (deflection) is 4.0-10.0mm (1335, 1487 and 1600cc engines) or 4.5-9.5mm (1751cc engines). This is measured right before the cable enters the throttle shaft bellcrank.
  4.  
  5. If deflection is not to specifications, rotate the cable adjusting nuts in the required direction.
  6.  
  7. As a final check, have a friend press the gas pedal all the way to the floor, while you look down inside the throttle bore checking that the throttle plates reach the wide open throttle (WOT) vertical position.
  8.  
  9. Install the air cleaner.
  10.  

Choke
1170cc AND 1237cc MODELS

The choke valve should be FULLY OPEN when the choke knob is pushed IN and/or FULLY CLOSED with the choke knob pulled OUT . The choke valve is held in the fully closed position by spring action. Pull the choke knob to the fully closed position, then, open and close the choke valve by rotating the choke valve shaft. The movement should be free and unrestricted.

If adjustment is required, adjust the cable length by loosening the cable clamp bolt.

Precision Adjustment
1170cc AND 1237cc MODELS

See Figure 6

  1. Using a wire gauge, check the primary throttle valve opening, dimension when the choke valve is fully closed. The opening should be 1.28-1.68mm.
  2.  



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Fig. Fig. 6: Precision choke adjustment-1170, 1237cc models

  1. If the opening is out of specification, adjust it by bending the choke rod. After installing make sure that the highest fast idle speed is 2,500-2,800 rpm while the engine is warm.
  2.  

When adjusting the fast idle speed, be sure the throttle adjusting screw does not contact the stop.

1487cc (1975-79) AND 1600cc MODELS
  1. Push the choke actuator rod towards its diaphragm, so it does not contact the choke valve linkage.
  2.  
  3. Pull the choke knob out to the 1st detent (click) position from the dash. With the knob in this position, check the distance between the choke butterfly valve and the venturi opening with a 3 / 16 drill (shank end).
  4.  
  5. Adjust as necessary by bending the relief lever adjusting tang with needle nose pliers.
  6.  
  7. Now, pull out the choke knob to its 2nd detent position from the dash. Again, make sure the choke actuator rod does not contact the choke valve linkage.
  8.  
  9. With the choke knob in this position, check that the clearance between the butterfly valve and venturi opening is 1 / 8 inches using the shank end of a 1 / 8 inch drill.
  10.  
  11. Adjust as necessary by bending the stop tab for the choke butterfly linkage.
  12.  

1335cc, 1487cc (1980-83) AND 1751cc MODELS
  1. With the engine COLD , remove the air cleaner.
  2.  
  3. Open and close the throttle all the way to engage the fast idle cam.
  4.  
  5. The choke plate should close to within 1 / 8 of the air horn wall.
  6.  
  7. If not, remove the choke cover and inspect the linkage for free movement. Repair or replace parts if necessary.
  8.  
  9. Install the cover and adjust so that the index marks align. Recheck the choke for proper closing clearance. If the clearance is not correct, replace the cap and retest.
  10.  

Choke Cable
1974-79 1237cc MODELS

See Figure 7

Perform the adjustment only after the throttle plate opening has been set and referenced.

  1. Make sure that the choke cable is correctly adjusted.
    1. With the choke knob in, the choke butterfly should be completely OPEN .
    2.  
    3. Slowly pull out the choke knob and check for slack in the cable. Remove any excessive free-play and recheck for FULL OPEN when the knob is pushed IN .
    4.  

  2.  
  3. Check the link rod adjustment by pulling the choke knob out to the 1st detent. The two scribed lines on the throttle control lever should align on either side of the reference tab. If not, adjust by bending the choke link rod.
  4.  



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Fig. Fig. 7: Choke cable adjustment-1974 and later 1237cc models. Number one is the detent position and number two is the link adjustment location

1487cc AND 1600cc MODELS
  1. Remove the air cleaner assembly.
  2.  
  3. Push the choke knob all the way in at the dash. Check that the choke butterfly valve (choke plate) is FULLY OPEN (vertical).
  4.  
  5. Next, have a friend pull out the choke knob while you observe the action of the butterfly valve. When the choke knob is pulled out to the 2nd detent position, the butterfly valve should just close. Then, when the choke knob is pulled all the way out, the butterfly valve should remain in the CLOSED position.
  6.  
  7. To adjust, loosen the choke cable locknut and rotate the adjusting nut so that with the choke knob pushed flush against the dash (open position), the butterfly valve just rests against its positioning stop tab. Tighten the locknut.
  8.  
  9. If the choke butterfly valve is sticky in operation or if it does not close properly, check the butterfly valve and shaft for binding. Check also the operation of the return spring.
  10.  

Throttle Valve Operation
1170cc AND 1237cc MODELS
  1. Check to see if the throttle valve opens fully when the throttle lever is moved to the fully open position. See if the valve closes fully when the lever is released.
  2.  
  3. Measure the clearance between the primary throttle valve and the chamber wall where the connecting rod begins to open the secondary throttle valve. The clearance should be 5.6-6.0mm.
  4.  
  5. If the clearance is out of specification, adjust by bending the connecting rod.
  6.  

After adjusting, operate the throttle lever and check for any sign of binding.

Accelerator Pump
1170cc AND 1237cc MODELS

Check the pump for smooth operation. See if fuel squirts out of the pump nozzle by operating the pump lever or the throttle lever. When the pump is operated slowly, fuel must squirt out until the pump comes to the end of its travel. If the pump is defective, check for clogging or a defective piston. Adjust the pump by either repositioning the end of the connecting rod arm in the pump lever or the arm itself.

1975-79 1487cc AND 1600cc MODELS
  1. Remove the air cleaner assembly.
  2.  
  3. Check that the distance between the tang at the end of the accelerator pump lever and the lever stop at the edge of the throttle body the distance is 0.80-0.85mm (1975-77) or 14.5-15.0mm (1978-79). This corresponds to effective pump lever travel.
  4.  
  5. To adjust, bend the pump lever tang in the required direction.
  6.  
  7. Install the air cleaner.
  8.  

1980-83 1487cc AND 1751cc MODELS
  1. Remove the air cleaner.
  2.  
  3. Make sure that the pump shaft is moving freely throughout the pump stroke.
  4.  
  5. Check that the pump lever is in contact with the pump shaft.
  6.  
  7. Measure between the bottom end of the pump lever and the lever stop tang. The gap should be 14-15mm through 1980 or 11.5-12.0mm (1981-83). If not, bend the tang to adjust.
  8.  

REMOVAL & INSTALLATION



See Figures 8 through 16

  1. Disconnect the negative battery cable. Disconnect (mark for correct installation) the following:
    1. Hot air tube.
    2.  
    3. Vacuum hose between the one-way valve and the manifold at the manifold.
    4.  
    5. Breather chamber (on air cleaner case) to intake manifold at the breather chamber.
    6.  
    7. Hose from the air cleaner case to the valve cover.
    8.  
    9. Hose from the carbon canister to the carburetor, at the carburetor.
    10.  
    11. Throttle opener hose at the throttle opener.
    12.  

  2.  
  3. Disconnect the fuel line at the carburetor. Plug the end of the fuel line to prevent dust entry.
  4.  
  5. Disconnect the choke and throttle control cables.
  6.  
  7. Disconnect the fuel shut-off solenoid wires.
  8.  
  9. Remove the carburetor retaining bolts and the carburetor (do not turn assembly upside down). Leave the insulator on the manifold.
  10.  

After removing the carburetor, cover the intake manifold parts to keep out foreign materials.

  1. Installation is the reverse of the removal procedure (replace mounting gasket). Torque the mounting bolts evenly. Adjust the carburetor. Road test the vehicle for proper operation.
  2.  



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Fig. Fig. 8: Removing the air cleaner for carburetor removal



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Fig. Fig. 9: Mark all vacuum hoses and lines for carburetor removal



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Fig. Fig. 10: Removing the carburetor mounting bolts



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Fig. Fig. 11: Removing the carburetor mounting nuts



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Fig. Fig. 12: Removing the carburetor assembly



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Fig. Fig. 13: View of the carburetor mounting area



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Fig. Fig. 14: View of the carburetor adaptor plate



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Fig. Fig. 15: View of the carburetor mounting gaskets



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Fig. Fig. 16: Close off the carburetor mounting hole with a shop towel

OVERHAUL



All Types

See Figure 17

Efficient carburetion depends greatly on careful cleaning and inspection during overhaul since dirt, gum, water or varnish in or on the carburetor parts are often responsible for poor performance.

Overhaul your carburetor in a clean, dust-free area. Carefully disassemble the carburetor, referring often to the exploded views. Keep all similar and look-alike parts segregated during disassembly and cleaning to avoid accidental interchange during assembly. Make a note of all jet sizes.

When the carburetor is disassembled, wash all parts (except diaphragms, electric choke units, pump plunger and any other plastic, leather, fiber or rubber parts) in clean carburetor solvent. Do not leave parts in the solvent any longer than is necessary to sufficiently loosen the deposits. Excessive cleaning may remove the special finish from the float bowl and choke valve bodies, leaving these parts unfit for service. Rinse all parts in clean solvent and blow them dry with compressed air or allow them to air dry. Wipe clean all cork, plastic, leather and fiber parts with a clean, lint-free cloth.

Blow out all passages and jets with compressed air and be sure that there are no restrictions or blockages. Never use wire or similar tools to clean jets, fuel passages or air bleeds. Clean all jets and valves separately to avoid accidental interchange.

Check all parts for wear or damage. If wear or damage is found, replace the defective parts. Especially check the following:

  1. Check the float needle and seat for wear. If wear is found, replace the complete assembly.
  2.  
  3. Check the float hinge pin for wear and the float(s) for dents or distortion. Replace the float if fuel has leaked into it.
  4.  
  5. Check the throttle and choke shaft bores for wear or an out-of-round condition. Damage or wear to the throttle arm, shaft or shaft bore will often require replacement of the throttle body. These parts require a close tolerance of fit; wear may allow air leakage, which could affect starting and idling.
  6.  

Throttle shafts and bushings are not included in overhaul kits. They can be purchased separately.

  1. Inspect the idle mixture adjusting needles for burrs or grooves. Any such condition requires replacement of the needle, since you will not be able to obtain a satisfactory idle.
  2.  
  3. Test the accelerator pump check valves. They should pass air one way but not the other. Test for proper seating by blowing and sucking on the valve. Replace the valve if necessary. If the valve is satisfactory, wash the valve again to remove breath moisture.
  4.  
  5. Check the bowl cover for warped surfaces with a straightedge.
  6.  
  7. Closely inspect the valves and seats for wear and damage, replacing as necessary.
  8.  
  9. After the carburetor is assembled, check the choke valve for freedom of operation.
  10.  

Carburetor overhaul kits are recommended for each overhaul. These kits contain all gaskets and new parts to replace those that deteriorate most rapidly. Failure to replace all parts supplied with the kit (especially gaskets) can result in poor performance later.

Some carburetor manufacturers supply overhaul kits of three basic types: minor repair; major repair; and gasket kits. Basically, they contain the following:

Minor Repair Kits:


All gaskets
 
Float needle valve
 
Volume control screw
 
All diaphragms
 
Spring for the pump diaphragm
 

Major Repair Kits:


All jets and gaskets
 
All diaphragms
 
Float needle valve
 
Volume control screw
 
Pump ball valve
 
Main jet carrier
 
Float
 
Complete intermediate rod
 
Intermediate pump lever
 
Complete injector tube
 
Some cover holddown screws and washers
 

Gasket Kits:


All gaskets
 

After cleaning and checking all components, reassemble the carburetor, using new parts and referring to the exploded view. When reassembling, make sure that all screws and jets are tight in their seats, but do not overtighten, as the tips will be distorted. Tighten all screws gradually, in rotation. Do not tighten needle valves into their seats; uneven jetting will result. Always use new gaskets. Be sure to adjust the float level when reassembling.



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Fig. Fig. 17: Exploded view of Keihin 3-bbl used on CVCC engines

 
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