Carburetor Service; Aisan Carburetor - Models 290700, 303700, 350700 (After 950930Xx) - Vanguard OHV V-Twin User Manual

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Fig. 20

Carburetor Service

Aisan Carburetor

Models 290700, 303700, 350700

(After 950930xx)

Check Throttle, Choke Shaft and Body For Wear

NOTE: The measurement in Step 1 is taken with the

carburetor off of the intake manifold.

1. Lay carburetor on flat surface and check throttle

and choke shaft clearance (1) as shown, Fig. 21.

Fig. 21

Throttle shaft and choke shaft clearance must not

exceed 0.010" (0.25 mm).

NOTE: The inspection in Step 2 is performed after

the carburetor has been disassembled.

2. Inspect throttle shaft and choke shaft for wear

(2), Fig. 22.

Fig. 22

Replace either shaft if worn.

Replace the carburetor if the body is worn or if either

shaft clearance exceeds 0.010" (0.25 mm) when a

new shaft is used.

Disassemble

1. Remove anti-afterfire solenoid (1) or bowl screw

(5) and washer (4), Fig. 23.

2. Remove float bowl (3). Discard bowl gasket (2).

Fig. 23

3. Remove float hinge pin (6), float and inlet

needle, Fig. 24.

CAUTION: Float hinge pin is a press fit.

Use care when removing.

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Troubleshooting

Need help?

Do you have a question about the OHV V-Twin and is the answer not in the manual?

Questions and answers

Kerry Ahlstrom

March 2, 2025

vanguard 18 HP Twin is running too rich and manual poorly illustrated and described

1 comments:

Mr. Anderson

March 2, 2025

To troubleshoot a Vanguard OHV V-Twin 18 HP engine running too rich, follow these steps:

1. Check Air Filter – A clogged air filter restricts airflow, causing a rich mixture. Clean or replace the air filter if necessary.
2. Inspect Carburetor – Ensure the carburetor is clean and free of debris. If needed, disassemble and clean it, replacing old gaskets and seals.
3. Examine Fuel Solenoid – The fuel shut-off solenoid controls fuel flow. Ensure it is functioning correctly and not stuck open.
4. Check Main Jets – Remove and inspect the main jets for blockages or excessive wear that could alter fuel flow.
5. Verify Choke Operation – Ensure the choke control is properly adjusted and not stuck in a closed or partially closed position.
6. Monitor Oil Type – Using the correct oil viscosity helps maintain proper engine operation. Avoid multi-viscosity oils in high temperatures if they increase oil consumption.
7. Inspect Cooling System – Overheating can affect air-fuel mixture. Clean the cooling system to prevent airflow restrictions.

If the issue persists, further carburetor adjustments or professional servicing may be required.