Section 5 Fuel System and Governor 5.6 Troubleshooting – Carburetor Related Causes Condition Possible Cause/Probable Remedy 1. Engine starts hard, runs roughly or stalls at idle speed. 1a. Low idle fuel mixture/speed improperly adjusted. Adjust the low idle speed screw. b. Low idle fuel mixture circuit blocked/restricted. Clean carburetor as required. 2. Engine runs rich (indicated by black, sooty exhaust smoke, misfiring, loss of speed and power, governor hunting, or excessive throttle opening). 2a. Clogged air cleaner. Clean or replace. b. Choke partially closed during operation. Check the choke lever/ linkage to ensure choke is operating properly. c. Float level too high.
Separate fuel bowl from carburetor body. Free (if stuck), or replace float. d. Dirt under the fuel inlet needle. Remove needle; clean needle and seat and blow with compressed air. e. Bowl vent or air bleeds plugged. Clean vent, ports, and air bleeds. Blow out all passages with compressed air. f. Leaky, cracked, or damaged float. Submerge float to check for leaks. 3. Engine runs lean (indicated by misfiring, loss of speed and power, governor hunting, or excessive throttle opening). 3a. Float level too low. Separate fuel bowl from carburetor body. Free (if stuck), or replace float. b. Idle holes plugged; dirt in fuel delivery channels.
Clean main fuel jet and all passages; blow out with compressed air. 4. Fuel leaks from carburetor. 4a. Float stuck. See Remedy 2d. b. Dirt under fuel inlet needle. See Remedy 2e. c. Bowl vents plugged. Blow out with compressed air. d. Carburetor bowl gasket leaks. Replace gasket. Troubleshooting Checklist • Make sure the air cleaner base and carburetor are When the engine starts hard, runs roughly or stalls at securely fastened to the engine using gaskets in low idle speed, check the following areas before good condition. adjusting or disassembling the carburetor.
• Make sure the air cleaner element is clean and all • Make sure the fuel tank is filled with clean, fresh air cleaner components are fastened securely. gasoline. • Make sure the ignition system, governor system, • Make sure the fuel tank cap vent is not blocked exhaust system, and throttle and choke controls and that it is operating properly. are operating properly. • Make sure fuel is reaching the carburetor. This If the engine is hard-starting or runs roughly, or stalls includes checking the fuel shut-off valve, fuel at low idle speed, it may be necessary to service the tank filter screen, in-line fuel filter, fuel lines and carburetor.
fuel pump for restrictions or faulty components as necessary.