Yamaha F4BMHS Troubleshooting
| Engine Model: Yamaha F4BMHS |
| Engine Type: 4-stroke 1-cylinder OHV short shaft gasoline outboard engine |
| Total Displacement: 8.5 cu.in (139 cc) |
| Rated Engine Power: 4 Hp (2.9 kW) at 5000 rpm |
| Fuel System: Carburetor |
____________________________________________________________________________________
| Engine won't start or starts hard |
Empty fuel tank - Add fuel.
Low-quality gasoline - Use quality gasoline.
Air in fuel system - Bleed fuel system.
Spark plug wiring connection is damaged - Inspect spark plug wiring connection, change or repair.
Faulty spark plug - Change spark plug.
Fuel filter is clogged - Replace or clean fuel filter.
Carburetor is not adjusted - Check carburetor float adjustment.
Clogged fuel lines - Fuel lines need to be cleaned.
Closed or clogged fuel tank air vent - Open or clean air vent.
Defective fuel pump - Install new fuel pump or rebuild it.
Incorrectly adjusted or damaged throttle cable - Change cable or adjust properly.
Valve clearance is improper - Adjust valve clearance according to specifications.
Valve timing is wrong - Adjust valve timing correctly.
| Engine starts but immediately stops |
Damaged spark plug - Install new spark plug.
Defective or dirty carburetor - Service or replace carburetor.
Faulty ignition coil - Change ignition coil as required.
Closed or clogged fuel tank air vent - Fuel tank air vent need to be opened or cleaned.
Fuel pump malfunction - Install new fuel pump or rebuild it.
Choke system malfunction - Check and repair choke system.
Valve clearance is wrong - Adjust valve clearance according to specifications.
Valve timing is wrong - Set the valve timing properly.
Damaged or weak valve springs - Valve springs need to be changed.
Stuck valves - Valves must be cleaned.
Ignition system is defective - Check ignition and replace faulty components.
Fuel pump is defective or dirty - Clean or change fuel pump.
Carburetor is not working properly - Inspect and adjust.
Clogged fuel lines - Fuel lines need to be cleaned.
Fuel tank air vent restricted or closed - Fuel tank air vent need to be opened or cleaned.
Fuel filter is plugged - Install new filter.
Gaskets are worn - Replace gaskets.
Clogged water intake - Need to clean or wash.
Choke system is damaged - Inspect and replace choke system components.
Engine is overloaded - Reduce engine load.
Carburetor is running lean - Adjust carburetor correctly.
Ignition timing is wrong - Set the ignition timing properly.
Defective thermostat - Install new thermostat.
Defective water pump - Replace water pump.
Propeller selection improperly - Check the propeller size.
Damaged or bent propeller - Replace propeller.
Outboard motor is mounted too high or too low - Mount the motor as required.
Engine oil level low - Check and refill engine oil.
Damaged oil pump - Change oil pump.
Clogged water intake - Clean and wash as required.
Wrong valve setting - Adjust valves correctly.
| Engine knocking sound or abnormal noise |
Low octane gasoline - Use correct gasoline.
Engine is overloaded - Reduce load.
Incorrectly adjusted low idle speed - Correct idle settings.
Fuel pump is defective or dirty - Check fuel pump and replace if necessary.
Crankshaft or main bearings wear - Have bearings or crankshaft replaced.
Cylinder bore or piston rings are worn - Change faulty parts.
Carburetor is clogged or incorrectly adjusted - Clean or properly adjust carburetor.
Fuel pump is faulty or clogged - Test fuel pump and change if necessary.
Defective ignition - Check ignition and replace faulty components.
Cylinder head gasket is blown - Install new cylinder head gasket.
Damaged powerhead components - Replace defective parts as required.
Burned or stuck valves - Service or change valves.
Incorrect propeller selection - Check the propeller size.
Damaged or bent propeller - Replace propeller.
Motor mounted at incorrect height on transom - Check the outboard engine mounting height.
Incorrect trim angle - Adjust trim angle correctly.
| Engine uses too much fuel |
Incorrect carburetor main jet adjustment - Adjust it correctly.
Spark plug is faulty or loose - Replace or tighten spark plug.
Rings, sleeve, or piston are damaged - Replace defective parts as required.
| Excessive motor vibration |
Propeller bent or damaged - Replace propeller.
Propeller shaft malfunction - Have propeller shaft replaced.
Weeds clogs the propeller - Remove weeds from propeller.
Motor mounting bolt is loose - Tighten the bolt as required.
Damaged or loose steering pivot Tighten correctly or replace.
____________________________________________________________________________________
| Outboard Engines Technical Specifications |
| Small Engines Technical Specifications |
| Car Engines Technical Specifications |
| Industrial Engines Technical Specifications |
