How to tell if lawn mower crankshaft is bent? Common symptoms with solutions

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While using the lawnmower, you will face some problems with this machine. In the previous article, we mentioned fixing plastic gas tanks in the lawn mower

Today, we will talk about a new issue that is lawn mower crankshaft. If you’ve used a mower, you may have had this problem. And many users don’t know how to fix it.

The crankshaft can cause terrible accidents for you, so you have to learn about it. But how to tell if lawn mower crankshaft is bent? Keep in mind in the article below and we will tell you all about it. 

Where does a bent crankshaft come from?

As you know, the blade of your lawnmower always rotates at very high rpm. Some mowers have an rpm of around, but it can reach 3000rpm/around or more. With that speed, when the crankshaft hits an immovable obstacle, it can be bent.

How to tell if lawn mower crankshaft is bent?  

An immovable obstacle can be a fence, a rock, a sprinkler, or something more. When your lawnmower hits one of them while the engine is still running, 100% it will be bent.

During maintenance and repair, the crankshaft was installed incorrectly as another reason for the bent crankshaft. You can complain to the repair facility or the place where you guarantee the product. I’m sure they will repair it for you or completely replace the crankshaft.

Please pay a little attention to the machine during operation to find out what causes the bent crankshaft. It can help you avoid many bad problems after.

How to tell if the lawn mower crankshaft is bent?

Typical symptoms of a bent lawnmower crankshaft

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1. Excessive vibrations

The first symptom is excessive vibrations. During operation, the machine produces abnormal vibrations continuously and especially makes loud noises. Those are obvious signs of a bent or broken elbow. These symptoms only occur when the crankshaft part of the machine has been bent or broken.

Related Post: Why my riding lawn mower vibrates When blades engaged?

2. The transmission

The second symptom is related to the transmission. This is quite an important issue. For a machine to work properly, all the parts of the machine need to work well and smoothly. The damaged crankshaft of the machine will cause collisions with other parts, making the transmission system inoperable. If this happens, you will meet a lot of difficulty in starting and operating the machine.

Physically inspect for a bent crankshaft

A physical inspection of the lawnmower is very important. We need to know the situation of the machine when the symptoms begin to appear before they become too serious.

1. The GAP between the Crankshaft and the Deck

The first thing that comes to mind when doing a physical inspection of a lawnmower is a broken crankshaft. That is to check the clearance between the crankshaft and the deck. If the clearance changes as you rotate continuously, your crankshaft is bent and needs repair. When performing this method, always remember to disconnect the spark plug first.

2. Look for Bolt Wobble

With this method, we will first disconnect the spark plug. Then have someone pull the cord to start the lawn mower. Meanwhile, watch the bolt that holds the blade to the crankshaft if any movement or wobbling means the crankshaft is bent and in need of repair.

3. Use a Dial Indicator

The dial indicator is an instrument with a dial that measures or detects minimal changes in distance and amplification that can be observed by anyone. At the same time, we can also use it to check if the elbow is bent or not. We just need to place the dial indicator at a specific point on the elbow and we will get what we want.

4. Look for blade wobble

Just like the swinging bolt of the crankshaft is bent, so the swinging saw blade is also a harbinger of the bent of the crankshaft. To see the blade, let the machine start on flat terrain. Watch it carefully if it is shaken it could be due to a broken blade but do not rule out the possibility that the crankshaft of the machine is bent.

Watch this video to learn more about “How to know if the lawn mower crankshaft is bent?”:

How to fix a bent crankshaft?

bent crankshaft

Damage to the crankshaft is one of the serious problems that must be overcome if the machine is to function normally again. Here are some solutions to fix this problem.

1. Using the Shaft Straighteners

In this method, we will use a straightener to straighten the bent shaft. We will use mechanical force to act on the shaft in a required position. Can be applied in both hot and cold shafts. This is an extremely effective method to return the shaft to its original state to keep the machine working properly.

2. Sledgehammers

This method is more basic and easier than using shaft straighteners but the efficiency is not as high. The only difference between these two methods is that when using a hammer we will apply a direct force on the crankshaft and when using a shaft straightener we will apply a direct force on the shaft.

3. Replacing a Bent Shaft

In cases where the elbow is too bent to be repaired as it was, this is the last resort. Do not try too hard to repair this part of the machine as it can easily lead to damage to other parts of the machine. When replacing a new shaft make sure the shaft is suitable for your lawnmower motor.

Check How to fix a bent crankshaft on Youtube:

Final thoughts

The bent crankshaft can cause terrible accidents for users. The most common disasters are foot abrasions, scratches, and worse, the loss of toes, half a foot,… To avoid these cases, please pay attention to your mower even if it’s just a small change. The visible signs are unusual noises from the machine.

Although there are some problems during use, the lawnmower usually is an incredibly useful machine. It can help make your landscapes more beautiful. Using these devices is not hard. But it’s vital to recognize any sign as soon as possible. 

Please use the mower carefully for the best results. Hope today’s article helps you know: How to tell if lawn mower crankshaft is bent?. Have a nice day!

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