The following are common faults and solutions:
I. Failure to start
Check the fuel system:
Ensure there is fuel in the tank, whether the fuel switch is turned on, and whether the oil circuit is blocked (you can remove the oil pipe and blow it through with your mouth).
Check if the carburetor is carbonized or blocked. Remove the float chamber to clean impurities, and replace the carburetor filter if necessary.
Check the ignition system:
Pull out the spark plug and observe if the electrode is wet (it may be flooded; remove the spark plug, pull it several times empty, dry it and reinstall it).
Test whether the spark plug sparks with a multimeter. If there is no spark, check if the high-voltage pack, ignition coil or circuit is damaged.
Check the cylinder pressure:
Measure the pressure with a cylinder pressure gauge. If the pressure is too low, it may be due to worn piston rings or a leaking cylinder gasket, which requires disassembly and maintenance.
II. Easy to stall after starting
Insufficient fuel supply:
Clean the fuel filter and check if the vent hole of the fuel tank cap is blocked (poor ventilation will cause negative pressure).
Adjust the carburetor idle screw (turn clockwise to increase idle speed, counterclockwise to decrease), to ensure stable idle speed.
Cooling system failure:
Check if the water pump is pumping water (there should be continuous water flow from the exhaust pipe after starting). If there is no water, check if the impeller is damaged or the filter screen is blocked.
Unstable ignition:
If the spark plug gap is too large or there is carbon deposit, readjust the gap (usually 0.8-1.0mm) or replace the spark plug.
III. Insufficient power
Abnormal air/fuel mixture ratio:
Clean the air filter. If the filter element is too dirty, replace it with a new one (paper filter elements cannot be washed with water; sponge filter elements can be cleaned with gasoline and then dried).
Adjust the carburetor main jet screw (turn clockwise to enrich the mixture, counterclockwise to lean it) until the engine runs smoothly.
Wear of mechanical parts:
Check if the gearbox oil is deteriorated or leaking. Worn gears will reduce power transmission efficiency, so the gear oil or gears need to be replaced.
If the propeller is deformed or entangled with debris, remove it for cleaning or replacement to ensure smooth rotation.
IV. Abnormal noise
Abnormal noise from the gearbox:
It may be due to insufficient gear oil or mixing with metal debris. Stop the machine immediately for inspection, replace the gear oil and check if the gears are damaged.
Abnormal noise inside the engine:A knocking sound may be caused by worn piston rings or detonation (check if the fuel label is too low); a cylinder scuffing sound may be caused by overheating due to insufficient engine oil, which requires disassembly and maintenance.
Belt slipping noise:
Check the belt tension. Too loose a belt will cause slipping; adjust the tension pulley or replace the belt.
V. Oil leakage/water leakage
Fuel leakage:
Check if the oil pipe interface is loose, replace aging oil pipes or clamps; if the carburetor float needle valve is not sealed tightly, the needle valve assembly needs to be replaced.
Oil leakage:
Check if the oil pan gasket is aging or if the oil drain screw is not tightened. Replace the seal and retighten.
Water leakage in the cooling system:
If the water pump seal ring is aging or the water pipe is broken, replace the seal ring or water pipe to ensure good sealing at the joints.
VI. Failure to restart after stalling
It may be hot engine flooding:
Fuel in four-stroke engines is easy to vaporize when hot, resulting in an over-rich mixture. You can remove the spark plug, pull the engine several times empty, and start it after the oil and gas in the cylinder are discharged.
