How to Tell if Lawn Mower Crankshaft is Bent – Latest Tips

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You may have the experience of facing the bent crankshaft on your lawn mower, whether that is a push-mower or a driving-type one. The crankshaft of the lawnmower can bend because of various reasons. To identify and solve this problematic situation, you should locate the crankshaft and know how to tell if the lawn mower crankshaft is bent.

When you will locate the place and identify the problem, you can take the necessary steps to solve it. You can repair the bent crankshaft if the bents are small and easily repairable. But you may have to replace the lawnmower’s crankshaft if the bent in there is quite severe and doesn’t come off.

The Reasons Behind A Bent Crankshaft of Your Lawn Mower

There are many reasons which can cause the crankshaft bent of your riding or push mower. But before that, you will have to locate the place where the crankshaft is situated. The causes of a bent crankshaft are:

  • Collision of the blade with something solid and immovable objects like a rock, pipes, sprinkles can cause the crankshaft to bent.
  • At the time of the installation, the crankshaft can fall on the strong surface, and that is another reason for the crankshaft bent.
  • There can be bent on the crankshaft at the time of manufacturing, and that will remain on the body of the crankshaft.
  • When you will be cleaning the crankshaft, improper process and less carefulness can also leave bent on the crankshaft.

How to Tell if Lawn Mower Crankshaft is Bent – All the Methods and Processes

Having bent on the crankshaft is not an unusual thing to happen, and you may have to face this issue at some point. Then, you will either need to repair the crankshaft or have to replace it. To do so, you will need to know the process and methods of telling whether your lawnmower crankshaft is bent or not.

You can tell if the lawnmower crankshaft is bent or not with two effective methods, and those are:

  1. Judging Through the Symptoms
  2. Inspecting the Lawn Mower Physically

Judging Through the Symptoms

You must need to regularly maintain your lawnmower and always keep a close eye on the odd symptoms. If you find the signs earlier, the mower will be saved from broader damages. There will be some odd symptoms shown by it if there is any bent on your lawnmower’s crankshaft.

Judging through those symptoms, you can tell whether your lawnmower’s crankshaft is bent or not, and those symptoms are:

A) Excessive Vibration of the Lawn Mower and the Engine.

B) Having Issues in the Transmission Process.

A) Excessive Vibration of the Lawn Mower and the Engine

Keep your eyes and ears alert when you will be cutting grasses off your lawn with your lawnmower. The engine or the mower body may start producing a grinding sound all of a sudden during your mowing session. Both the mower and the mower-engine can also produce odd vibrations, and the vibration or grinding sound doesn’t have to occur continuously.

The vibration and odd grinding sound can suddenly appear and disappear right after some time. With these signs appearing, you can tell your lawnmower crankshaft is bent.

B) Having Issues in the Transmission Process

The lack of transmission will cause problems during the start of the lawnmower engine. You will face hiccup during the running times because of the transmission issues. This lack of transmission issues will occur when the lawnmower crankshaft is bent. The ignition process will also be hampered, along with the bent crankshaft hitting the flywheel.

Inspecting the Lawn Mower Physically

When you will run a physical inspection on your lawnmower to find the bent in the crankshaft, you can use two of the common and effective methods. The two methods are:

Method-1: Gap Measuring Method

Necessary tools for this process are:

  • A ruler and a pencil – You will need these tools for the marking purpose.

Step-1: Placing the Lawnmower and Spark Plug Disconnecting

At first, find an even surface area to stand the mower. Make sure the surface area is clean without any ups and downs. Then place the lawnmower in that place, and with the help of another person, turn the mower body upside down. Before you turn the mower body, carefully disconnect the spark plug wire.

Step-2: Marking

Then take a ruler and a pencil for the marking work. Mark the distance between the starting side of the cutting deck skirt and the edge where it will touch the crankshaft, and then measure the distance.

Step-3: Checking

After marking, turn the crankshaft and let it rotate for once. Then check the distance with the ruler again, and if the distance expands and expands consecutively, be sure that your lawnmower’s crankshaft is bent.

Method-2: Wobbling Bolts

Step-1: Disconnecting the Spark Plug

At first, you will have to detach the spark plug wire from the engine of the lawnmower. It will ensure your safety during the checking time. Then turn the mower body upside for the checking purpose with someone’s help. 

Step-2: Pull the Starting Cord and Check

Keep a person ready for this process as well, and tell him/her to pull the starting cord. At that time, you will have to keep your entire focus on the mounting bolts of the steel blade of your lawnmower. If you see the bolts wobbling, take it for granted that your lawnmower crankshaft is bent.

Taking the Necessary Steps

Considering the seriousness of the crankshaft bent, you will have to either repair the crankshaft, or you will have to replace it. When the bent will be simple, you can quickly fix the bent on the crankshaft by using some essential household tools. 

All these processes can be done at your garage or on the lawn as well. It won’t take a long time for the process to complete. 

Step-1: Prepare the Lawnmower

Disconnect the spark plug wire of the engine for safety purposes. Then, turn the mower body upside down over a strong concrete-surface. Detach the steel deck and the Sharp steel blade from the mower body.

Step-2: Access to the Shaft

Then, you will need to access the shaft by detaching it from the mower body by unmounting all the screws and the nuts-bolts.

Step-3: Repairing the Shaft

After accessing, find the place where the bent is and repair it using the necessary tools. Once the crankshaft bent will be cleared, put the crankshaft back in its place, and re-assemble the lawnmower’s parts.

You can also replace the crankshaft by accessing it first and then replace the faulty and bent crankshaft with a brand new one.


Can a lawnmower crankshaft bend?

Yes, of course, your lawnmower’s crankshaft can bend. It can bend while the blade will come in contact with solid and unremovable things like rocks, pipes, or sprinkles.

What should I do if my lawnmower crankshaft is bent?

If your lawnmower crankshaft is bent, you will need to check it first. Then, detach the crankshaft from the mower body, repair it, or replace it considering the seriousness of the situation and the damage.


Finding the problem and problematic place first and then going for the solving process is the wise decision under every circumstance. This method also applies when your lawnmower crankshaft is bent. You will have to understand by seeing the signs and symptoms that the crankshaft is bent, then try to solve this bent problem.

To acquire knowledge in this sector, I would recommend you to take advice from an experienced person. Telling if the lawnmower crankshaft is bent or not comes gradually with acquiring experiences.

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