Repeated tugs on the pull-start line for your lawnmower cause an annoying sputtering in the engine. Or maybe the engine roars to life, shows promise and then conks out again. Your lawnmower thwarts your grand plans to mow your lawn for the first time this season. This lack of cooperation often points to a filthy carburettor. Carburettors mix air and gasoline in the correct amounts to create a combustible mixture. They also create a perfect combination of air and fuel to fire the engine and control engine speed. Cleaning you lawnmower's carburettor will have you mowing before you know it and should be part of your mower's regular maintenance.
Roll the mower to a flat surface and turn off the fuel line. Locate the nut below the bottom of the carburettor and twist to remove. Place it in a safe spot for later reassembly. Removal of the bottom of the carburettor may result in some draining of gasoline so place newspapers underneath to absorb the old fuel.
Spray carburettor cleaner inside the bottom cup of the carburettor, including praying the plastic float valve. Wipe it completely free of all gunk and debris. If you left gasoline in the mower over the winter, it breaks down to varnish, gumming up the inside of the carburettor. Removing all broken down gas, debris and dirt helps the engine fire more readily.
Spray carburettor cleaner into the remaining parts of the carburettor. Wipe it clean, removing every bit of varnish and gunk. Check every hole for clearance and use wire to clean clogged jets made of brass. Some individuals find using compressed air makes this job easier.
Reassemble the carburettor, making sure to replace every part correctly and tighten bolts. Finish the reassembly by securing the bolt on the bottom of the carburettor cup.
Turn the fuel line back on and prime the engine and give the pull start a good tug. Your lawnmower should fire right up. If it doesn't, you might have a clogged fuel line or an incorrect air/gas mixture.
Locate the carburettor's air adjustment valve. Turn the valve all the way to the right, then turn it left for two turns. This valve helps control the air/gas mixture. Try another pull start to see if the engine fires. Turn the air adjustment valve a little to the left for a smooth-running engine.