Lawn Mower Shakes Violently When Blades Engaged [Fixed]

Lawn Mower Shakes ViolentlyBy reading this troubleshooting guide, you will not only able to identify the causes, symptoms, and effects of why lawn mower shakes violently when blades engaged but also capable of fixing the shaking and vibrating issues of your lawnmower.

If your lawnmower makes you feel trembling, there can be several reasons behind it. But first of all, you need to bring your lawnmower on a smooth condition by stopping it.

The major causes behind this vibrating issue can be the blades or a crankshaft. Without getting panic or worry, you need to know that you can easily track, control, and fix them by simply reading the user manual. But in a critical situation, our guide will help you to fix and overcome the shaking issue in the future.

Why Lawn Mower Shakes Violently When Blades Engaged

First, we need to identify the exact causes and the reasons behind the vibration and the shaking of the lawnmower so that we can able to tackle the main cause and then head towards fixing.

Causes may include;

  • Unbalanced blades
  • Pollute blades
  • Unsharpened blades
  • Bent Crankshaft

Let’s have a deep look at each issue one by one to get the answer and to fix our main problem that why lawn mower shakes violently when blades engaged.

1. Unbalanced Blades – Why Lawn Mower Shakes Violently

Vibration or shaking is not a big deal when blades are moving with the speed of 200-240 mph and they are not sharped quite well, or it might be a possibility that after sharpening, they are not reinstalled properly. It causes the blades to get imbalanced which produces noise, vibration and makes the lawn mower shakes and rattles.

Balancing blades

Sometimes when blades strike with some hard material (stone, rock, or hard root) on the ground, it can also disbalance the blades or any other damage to them.

Balancing Blades

You need to;

  • Replace the damaged or unbalanced blades immediately.
  • Reinstall the blades properly.
  • Try to sharpen the blades on both sides to keep them evenly balanced by removing the extra metal from them.

Replacing the blades

  • You can easily replace or remove the blades by using the user manual.
  • Tilt the lawnmower to prevent fuel leakage and to keep the carburetor up.
  • Drain the excess fuel if needed, just to prevent fuel or oil from leaking through gaps.
  • Use a spanner for the safe and secure removal of blades.
  • Clean the blades thoroughly after removing them from the deck.
  • Use torque spanner of accurate size to install new blades and to harden them well.

2. Pollute blades

Sometimes, during mowing sessions, mud, clay, or clump of grass can stick on the blades of the lawnmower. It interrupts the movement of blades and extra weight makes it difficult for the blades to move properly. Due to this off-balance rotation, lawnmower starts shaking or vibrating.

polluted blades

How to fix pollute blades – Why Lawn Mower Shakes Violently

You can simply fix the pollute blades by;

  • Untie blades from the deck.
  • Make sure to clean them thoroughly by water, brush, and cloth if needed.
  • Reinstall them properly using a spanner and the user manual.

3. Unsharpened blades

After having long mowing sessions several times, blades need to sharpen properly and they need proper maintenance. By cutting a huge amount of grass, roots, and debris, blades become rough.

Unsharpened blades

How to fix unsharp blades – Why Lawn Mower Shakes Violently

  • You may need to check the balance of the blades while sharpening them.
  • For this purpose, you might need some devices to check and to keep them evenly balanced.
  • You can simply fasten the blade through the center hole on a peg or a nail in a wall.
  • The heavy side will drop lower than the other side.
  • Try continuous sharpening by removing extra metal, till the blades become stable and come at the equilibrium position.

4. Bent Crankshaft

Another major cause of excessive vibration and shaking during mowing is the bent crankshaft. Moreover, the blades, crankshaft also got bent by tapping or striking of a lawnmower with some hard and solid material.

Bent Crankshaft

Most of the time, the lawnmower vibration is the cause of this bent crankshaft. And sometimes the abrupt stopping of blades can cause the crankshaft to bend and vibrate.

How to Diagnose the damaged crankshaft

  • Remove the first possible cause of vibration, which is blades.
  • Run the mower without blades and be careful to notice the sound and the shaking after their removal.
  • If the lawnmower is again vibrating then it can cause by the damages crankshaft.
  • The next step is the removal of shaking causes.

How to fix it – Why Lawn Mower Shakes Violently

You can simply repair or fix the damaged crankshaft by following the mentioned steps;

  • After removing blades, it is necessary to check the crankshaft runout by using a dial indicator.
  • Eliminate the blades along with the blade mounting core and the spark plug from the lawnmower.
  • Attach the dial indicator to the deck and placed it on the crankshaft.
  • Carefully read the amount of runout on the indicator by gently twisting the engine.
  • Therefore, the value over .003″ verifies the crankshaft damage.
  • You can concern to the user manual for exact value according to your lawnmower.
  • You need to remove the complete engine step by step to replace the bent crankshaft.
  • Hire some professionals to service your engine and the lawnmower to avoid excess damage.

We hope this guide will help you out in identifying the symptoms and causes of excessive vibration in your lawnmower. And it may also help you to eliminate it, fix it, or repair it when your lawn mower shakes violently.

Ignoring the vibration will lead you and the lawnmower to the major mechanical or technical issues which sometimes are difficult to handle for an inexperienced person.

Follow this simple guide to diagnose the issue of excessive and violent vibration and try to fix it the way this guide teaches you. Otherwise, hire some professionals to tackle, handle, and fix the issue without making it severe.

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