Carburetor: Adjustments

INSPECTION:

1. Clean disassembled parts before inspection.
a. Clean parts with carburetor solvent. Soaking is the preferred method.
b. Do not soak rubber or vinyl parts.
c. Clean all carbon from around throttle valve.
d. Blow dirt and other foreign matter from all jets and carburetor passages.
2. Inspect float and needle valve assembly.

Float And Needle Valve Components:

a. Check pivot pin (1) for scratches and excessive wear.
b. Inspect float (2) for broken tangs and worn pivot pin holes.
c. Inspect the spring (3) for breaks and deformation.
d. Check the needle valve (4) and plunger (5) for wear or damage.
e. Inspect the strainer (6) for rust and breaks.
3. Inspect suction chamber and piston.

Suction Chamber And Piston:

a. Inspect the suction chamber (1) for damage and scratches in the suction chamber.
b. Inspect the suction piston (2) for damage and wear.
c. Inspect the metering needle (3) for damage and wear.
4. Inspect Fuel-Cut Solenoid valve operation.

Testing Fuel-Cut Solenoid Operation - Case Grounded:

a. Connect the black wire to a positive 12 volt battery terminal and the solenoid body to the battery negative terminal.
b. The solenoid should "click" when the battery power is connected and disconnected.
c. If a problem is found, replace the solenoid valve.
d. Repeat test, but using the white-black wire for negative connection.

Testing Fuel-Cut Solenoid Operation - Harness Grounded:

e. The solenoid should "click" when the battery power is connected and disconnected.
f. If a problem is found, replace the solenoid valve.
g. Always replace the tip O-ring before installation.
5. Inspect throttle position switch operation.

Checking Throttle Position Switch Continuity:

a. Connect an Ohmmeter to the switch connector and the switch body.
b. Push the rod tip in and check that there is no continuity.
c. Release the rod and check that there is continuity.
d. If a problem is found, replace the throttle switch.
6. Inspect fuel heater and cold mixture heater (CMH).

Measuring Fuel Heater Resistance:

a. Using an Ohmmeter, measure the resistance between the terminals of the fuel heater.

Resistance (Cold): 2 - 6 Ohms

b. If not as specified, replace the fuel heater element.
c. Using an Ohmmeter, measure the resistance between the terminals of the CMH.

Measuring Cold Mixture Heater Resistance:

Resistance (Cold): 0.5 - 2.2 Ohms

d. If not as specified, replace the CMH element.
7. Inspect throttle solenoid actuator.

Testing Throttle Solenoid Valve Actuator Operation - Current Applied:

a. Connect the solenoid terminals to battery current.
b. Check that the pushrod will not push in.
c. Disconnect battery current and push in pushrod and release it.

Testing Throttle Solenoid Valve Actuator Operation - Current Removed:

d. Check that it returns immediately to its original position.
e. If a problem is found, replace the throttle solenoid actuator.

FLOAT ADJUSTMENT:

1. Install the needle valve seat with a new gasket.
2. Install the needle valve, spring and plunger onto the seat. Do not install the pin clip at this time.
3. Install the float with the pivot pin.

Installing Float With Pin:

4. Invert the carburetor body and allow the float to hang by its own weight.

Measuring Dry Float Level:

5. Measure the clearance between the float tip and the carburetor surface.

Dry Float Level: 0.169 in. (4.3 mm)

6. If not as specified, remove the float and bend the float tang.

Bending Float Lip (Tang):

7. Check adjustment by repeating steps 3 - 5. Repeat as many times as necessary to achieve proper measurement.
8. Lift the float with your finger and check the clearance betweeen the needle valve plunger and the float lip.

Checking Clearance Between Float Lip And Needle Valve:

Float Clearance: 0.035 - 0.043 in.
(0.9 - 1.1 mm)

9. If not as specified, remove pivot pin and float. Adjust by bending the tang on the float.

Adjusting Float To Needle Valve Clearance:

10. Check adjustment by repeating steps 8 and 9. Repeat as many times as necessary to achieve proper measurement.
11. After adjustments are correct, remove the pivot pin, float and needle valve from air horn. Install these parts when directed to in carburetor REASSEMBLY AND INSTALLATION.

THROTTLE VALVE OPENING ADJUSTMENT:

1. Invert carburetor and open throttle valve to the full open position.

Check Throttle Valve Opening Angle:

2. Check that the throttle valve opens 87 - 93 degrees from the horizontal plane of the base flange.
3. If not as specified, bend the throttle lever stop for adjustment.

Adjusting Throttle Valve Lever Stop:

FAST IDLE ADJUSTMENT:

1. Set the fast idle adjusting cam to the roller of the throttle lever, as shown.

Checking Throttle Valve Angle For Fast Idle Setting:

2. Check the throttle valve angle with a gauge.

Standard Angle:
M/T 18.7° from the horizontal plane
A/T 19.0° from the horizontal plane

3. Adjust by turning the No.1 fast idle adjusting screw.

Adjusting No. 1 Fast Idle Screw:

(IDLE) COMPENSATOR ADJUSTMENT:

1. Separate the fast idle adjusting cam from the first idle lever.
2. Using a screwdriver, pry open a gap of at least 1/4 inch between the fast idle cam and the cold enrichment rod.

Opening A Gap Between The Fast Idle Cam And Cold Enrichment Rod:

3. Allow the gap to close and flush the compensator water pipe with ordinary tap water for 2 - 3 minutes.

Flushing The Compensator With Tap Water:

4. Apply vacuum to the throttle positioner diaphragms using a handheld vacuum pump.
5. Invert the carburetor and measure the throttle angle.

Measuring Throttle Angle With Vacuum Applied To TP Diaphragms:

6. Compare relationship to the temperature of the tap water. (Refer to chart)

Compensator Throttle Angle Chart:

NOTE: If the tap water temperature is not listed in the chart, select the closest temperature listed and use its corresponding angle.

7. Adjust by turning the No.2 fast idle adjusting screw.

Adjusting No.2 Fast Idle Screw:

THROTTLE POSITIONER (TP) ADJUSTMENT:

1. Remove wax back springs.

Removing Wax Back Springs:

2. Apply vacuum to TP diaphragms, using a handheld vacuum pump.

Applying Vacuum To TP Diaphragms:

3. Invert the carburetor and measure the throttle valve angle with a throttle angle gauge.

Measuring Throttle Angle With Vacuum Applied To TP Diaphragms:

Standard Angle: 13.2° from the horizontal plane

4. Adjust the TP by turning the adjustment screw.

Adjusting Throttle Positioner:

5. Install wax back springs. Make sure the spring hooks do not overlap.

Correct Installation Of Wax Back Springs:

PISTON UNLOADER ADJUSTMENT:

1. Open the throttle valve fully.
2. Measure the piston lift stroke through the air horn.

Measuring Piston Lift Stroke:

Standard Stroke: More than 0.31 in. (8.0 mm)

3. If not as specified, recheck throttle valve opening adjustment.

ACCELERATION PUMP STROKE ADJUSTMENT:

1. Work the throttle valve by hand and measure the pump stroke at the plunger.

Measuring Length Of Acceleration Pump Stroke:

Standard Stroke: 0.197 - 0.236 in.
(5.0 - 6.0 mm)

2. If not as specified, adjust the pump stroke by bending the connecting link.

Adjusting Acceleration Pump Stroke By Bending Linkage:

Setting Stroke: 0.217 in. (5.5 mm)

THROTTLE POSITION SWITCH ADJUSTMENT:

1. Check that the first idle cam and auxiliary idle cam do not move.

Checking First Idle Cam:

2. Connect Ohmmeter probes to the switch connector and the switch body.
3. With the throttle valve fully open, check that there is continuity.

Checking Throttle Position Switch Adjustment:

4. Slowly return the throttle valve from fully open.
5. At the point where there is NO continuity, measure the throttle valve angle.

Measuring Throttle Valve Angle:

Standard Angle: 11.5° from the horizontal plane

6. If not as specified, adjust the throttle switch adjusting screw.