Will a Damaged Flywheel on a Lawn Mower Affect How Fast the Blades Turn?
- The flywheel can receive damage from hitting many different hard objects. The most common is hitting a rock while the mower is running at moderate to full speed. Other objects such as a curb or a stump can also cause flywheel damage. However, it takes a substantial hit to knock the flywheel off or to damage it in any way. Since the flywheel sits on the crankshaft, it will force the other moving parts out of alignment.
- Made of heavy metals, the flywheel should not damage easily. However, engine conditions may cause weaknesses in the metal. If a stressor is added, such as a rock, the already weakened metal may bend. If the engine operates regularly above normal temperatures, as it can if it has a dirty air filter or bad gas, the increase in temperature may weaken the flywheel metal over many years. Weakness can also occur if any object accidentally makes it into the interior part of the engine and rubs against the flywheel.
- The thin metal key that mates the flywheel onto the crankshaft stub can also sustain damage. Called a sheared flywheel key, the metal stub, or key, joining the two parts will bend nearly in half. This can happen if the flywheel takes a jarring hit from the blades hitting metal or a rock. If you have a sheared key, you'll need to remove the flywheel and install a replacement key onto the crankshaft to get the blades running at full speed again. This is less expensive than buying a new flywheel.
- Damage directly to the flywheel or its fins also usually requires flywheel replacement. To replace the flywheel, you'll need a special tool to remove it. Often called a flywheel puller, it attaches around the rim of the flywheel and slowly lifts it off the crankshaft stub after you remove the bolt. Don't use a metal hammer to pound the flywheel loose from the crankshaft, as you may damage the flywheel or the crankshaft. Replace any bent or damaged keys and check the flywheel thoroughly on both sides for cracks and dents.