Section 5 Fuel System and Governor Fuel Shut-Off Solenoid Most carburetors are equipped with a fuel shut-off solenoid. The solenoid has a spring loaded pin that retracts when 12 volts is applied to the lead. When power ceases, the spring loaded pin extends and blocks the main jet. 1 3 Below is a simple test made with the engine off that can determine if the solenoid is functioning properly. Use a separate, switched 12 volt power supply to test. 2 4 1. Shut off the fuel and remove the solenoid from the carburetor. When the solenoid is loosened and removed, gas will leak out of the carburetor. Have a container ready to catch the fuel. Figure 5-2. Valve Cover Torque Sequence. Carburetor 2.
Wipe the tip of the solenoid with a shop towel or blow it off with compressed air, to remove any remaining fuel. Take the solenoid to a location with good ventilation and no fuel vapors present. You will also need a 12 volt power source that can be switched on and off. General Engines in this series are equipped with emission compliant fixed main jet carburetors, manufactured by Keihin. All have self-relieving chokes for efficient operation. Depending on the specifications and application involved, most will also contain a fuel shut-off solenoid and an accelerator pump. An exploded view of the carburetor is shown in Figure 5-6, with the accelerator pump components shown in the inset. 3.
Be sure the power source is switched “off”. Connect the positive power source lead to the red lead of the solenoid. Connect the negative power source lead to the solenoid bracket. 4. Turn the power source “on” and observe the pin in the center of the solenoid. The pin should retract with the power “on” and return to its original position with the power off. Test several times to verify operation. Float Circuit: Fuel level in the bowl is maintained by the float and fuel inlet needle. The buoyant force of the float stops fuel flow when the engine is at rest.
When fuel is being consumed, the float will drop and fuel pressure will push the inlet needle away from the seat, allowing more fuel to enter the bowl. When demand ceases, the buoyant force of the float will again overcome the fuel pressure and stop the flow. Carburetor Adjustments General In compliance with government emission standards, the carburetor is calibrated to deliver the correct air- to-fuel mixture to the engine under all operating conditions. Both the low and the high speed mixture circuits are preestablished and cannot be adjusted. The low idle speed (RPM) is the only adjustment available.
High Altitude Operation When operating the engine at altitudes of 1500 m (5000 ft.) and above, the fuel mixture tends to get overrich. This can cause conditions such as black, sooty exhaust smoke, misfiring, loss of speed and power, poor fuel economy, and poor or slow governor response. NOTE: Low idle speed (RPM) adjustment should be made only after the engine has warmed up. To compensate for the effects of high altitude, a special high altitude main jet can be installed. High altitude jets are sold in kits which include the jet and necessary gaskets. Refer to the Parts Manual for the correct kit number. 5.4