How to Troubleshoot the Flywheel Key on a Lawnmower

Turn off the lawnmower and open the engine hood, if applicable, to access the engine. Wait several minutes for the mower's engine to cool before proceeding.

Locate the flywheel, which is an iron, circular "wheel" near the top of the back of the engine with an iron cover.

Take out the bolts that secure the cover to the flywheel with a socket wrench. Remove the cover.

Remove the exposed flywheel's center bolt with the wrench.

Place a flywheel pulley over the mower's exposed flywheel and lower the two pulley arms over the sides of the flywheel so they are secure.

Tighten the center bolt on the pulley with the wrench until the flywheel pops entirely free from the engine. You may need to tighten the pulley and leave it tightened for several minutes before the pressure causes the flywheel to pop free.

Locate the flywheel key, which is a small metal part that will be sitting vertically at the center of the flywheel assembly. Check the keyway along the middle of the key for any burrs and file them down if necessary. Additionally, file off any burrs on the fins of the actual flywheel itself.

Ensure that there is no debris within or under the flywheel around the flywheel key. Remove this as this can cause the flywheel key to sit incorrectly.

Verify that the flywheel key is seated upright and oriented vertically within the flywheel assembly. It must not be lying down.

Reassemble the flywheel, once the key is correctly in place, by reversing the steps for removal.