Important: When working on a pruner, remember that gasoline/gasoline is flammable. Remove all sources of ignition, such as flames, stoves, sparks, cigarettes, or other hot objects in the vicinity when working in the tank or fuel lines. In addition, proper ventilation will prevent buildup of steam. Do not leave wet rags with gas either because they may ignite.
- Remove the spark plug or unplug the cord. Before working on the underside of an engine, make sure the controls are off, the spark plug wire is disconnected and the motor has cooled down (if it was previously ripped off). If you are starting to turn the blade, remove the motor cap for absolute safety. In theory, it is possible, even if the plug cable is disconnected and the cylinder of a hot engine is flooded with gas, that the resulting vapor could explode when compressed by the piston, as in a diesel engine, as the blade is rotated during removal or While cleaning the bottom of the platform. Although the engine will not work, it may give a "kick" when turning the blade. This would be enough to cut your fingers or even a whole hand! Maybe it's a remote possibility, but removing the cap will vent the cylinder and prevent this from happening.
- Keep the carburetor side of the engine up to prevent oil spillage if the mower is side-mounted. The engine oil can also dirty the carburetor and air filter, making it difficult to start. The sump (the tank at the bottom of the engine that contains the oil) is vented to the atmosphere through a deflector/tab valve layout called a vent. Ventilation is necessary so that the air can come in and out of the sump as the piston moves in and out of the cylinder. The baffle prevents the oil droplets from escaping from the vent. In addition, some unburned gases can pass through the piston and into the crankcase. This would eventually cause an increase in pressure without the inclusion of a vent. The vent is sometimes connected to the carburetor through a tube, so any drop of oil that passes through the valve and the unburned gases are sucked into the engine and burned. (A defective vent valve may cause excess oil consumption.) The oil can come out through the vent if the motor rotates sideways with the vent down and the blade turned.
- Do not forget to drain the fuel tank if the mower is side-mounted. Otherwise, if the fuel level is higher than the vent on the tank cap, it may begin to drip. You can collect the gas in a jug or other suitable container (do not use one made of polystyrene that dissolves in gas). Alternatively, use a siphon pump designed for this purpose. If there is only a small amount of gas in the tank, then you do not need to do this.