Lawn mower shaft bent. How to Remove the Lawnmower Crankshaft From an Engine

How to Remove the Lawnmower Crankshaft From an Engine

Lawnmower crankshafts can get bent from the blade hitting a solid object while mowing, such as a tree root or rock. A crooked crankshaft can occasionally be straightened by heating and bending in a vice, but a severely bent shaft might have to be replaced. The connecting rod pin on the crankshaft will eventually wear enough to require a replacement crank after years of use.

The shaft is cast as one piece of steel, and much of the engine must be disassembled to get it out. Lawnmower engines in the 3 to 6-HP range require very similar procedures for crankshaft removal.

Remove engine fluids

Place a drain pan next to the lawnmower. Tilt the mower enough to gain access to the oil drain plug, and unscrew it with a socket wrench. Drain the oil from the lawnmower engine.

Use a pair of pliers to compress the fuel hose clamp where it attaches to the fuel tank. Remove the fuel hose from the gas tank and drain all of the gas out. Remove the gas cap and turn the mower on its side for an alternate drain method.

Remove the air filter housing, fuel tank or fuel tank/carburetor assembly.

Remove engine attachments

Use a Phillips-head or flat-blade screwdriver to unhook the throttle cable and engine cut-off cables, if so equipped.

Remove the oil tube dipstick, if so equipped.

Remove the pull-start cowl; on electric start models, remove the metal shroud which is bolted on the top of the engine.

lawn, mower, shaft, bent, remove

Disconnect the spark plug wire. Remove the ignition module or magneto and remove the spark plug.

Remove flywheel

Tap the round starter clutch (if so equipped) moderately with a rubber hammer in a counterclockwise direction to unscrew it from the crankshaft. Take the clutch off.

Unbolt the flywheel. Use a cheater bar or piece of wood to stabilize the flywheel while loosening the bolt. Be careful to not break any of the cooling fins.

Pry under the flywheel with a large flat-blade screwdriver while tapping on the crankshaft end with a rubber hammer. Use a flywheel puller if it still won’t break free. Remove the flywheel. Take out the shear pin from the crankshaft slot.

Remove engine

Turn the lawnmower on its side.

Wear work gloves, and grasp the blade along an un-sharpened section. Hold the blade firmly while rotating the blade bolt with a large wrench to loosen. Remove the bolt and blade.

Turn the mower upright. Locate the engine mount bolts which hold the engine and deck together.

Remove the bolts and the engine from the mower. Place the engine on a workbench for a more comfortable work space.

Remove Valve Spring

Remove the two small screws holding the valve cover in place and take off the cover.

Clamp the valve spring compressor tool onto the top of the spring on one end and between the metal washer and the spring end on the other. Compress the spring.

Jiggle the metal washer until it slides off through the notch on its edge. Remove the washer and slowly release the spring. Do not remove the spring from the chamber. Repeat this process with the other spring.

lawn, mower, shaft, bent, remove

Remove Crankshaft

Remove the lower engine case on the blade side of the engine. Slide the cover off gently—oil may run out as you take off the cover.

Grasp the camshaft gear and pull it free. Remove it.

Bend the retaining tabs downward from around the connecting rod end cap bolts. Unscrew the bolts and take off the rod end cap.

Press the connecting rod upward so the piston slides to the top of the cylinder. Turn the crankshaft until the connecting rod pin points away from the cylinder.

lawn, mower, shaft, bent, remove

Slide the crankshaft toward you and remove it from the engine.

Wash the engine exterior with engine cleaner and a spray nozzle before beginning. Place a large piece of cardboard underneath and around the work area.

Wait until the engine is cool before attempting this procedure. Keep your head away from the flywheel when breaking it free—it may suddenly snap upward. Use work gloves when removing the camshaft—the gear is rather sharp.

Introduction: How to Straighten and Sharpen a Lawnmower Blade

Bending lawnmower blade is never fun and can be very frustrating. If you’re ever unfortunate enough to bend one I hope this helps you fix it. So here’s how I did it I took me about ten minutes to do this repair.

Remember if you do this, the blade can break,so be careful and you your best judgement. At some point you will need to replace the blade, for me this point was after the fourth time Istraightened it

Step 1: Tools

For this repair I used:Ratchet with long handle A socket the size of the bolt on my mower

A pair a Channel lock pliers (any large pair on pliers will work)

And an anvil of you have one

Step 2:

Flip the mower up on one side it’s better to flip the mower so that the air filter is up so that gas or oil does not drain in to the air filter. Take the socket and wrench and remove the blade you will need something to brace the blade against, I usually do this with my foot. If you don’t want to use just your foot for this get a large price of scrap wood and put that between your foot and the lawn mower blade. Once the blade is removed flip it back over so that it sits on the ground like it should.

Step 3: Bend It

The best method I have found for doing this is to place the none bent end under the anvil and use a pair of channel locks to bend the blade back to fairly straight.If you don’t have access to a anvil it would work just as well to put the none bent end in a vise or even clamp it to the work surface with a very strong clamp.

Step 4: Hammer It

Take the ball peen hammer to flatten out the last of the bend I use the avil for this but if you don’t have access to one a sledgehammer will do the anvils job.

Step 5: Sharpen It

Grab the file and hold the straightened blade against your work table, use the file to sharpen the cutting edge of the blade, if you are having trouble finding this the cutting edge of the blade is usually the cleanest part of the blade. Put the file up to the blade and apply slight pressure and drag the file away from it. Make sure that all the strokes go away from the edge. It you happen to have the dremmel and lawnmower sharpening atackment or a bench grinder just use that.

Step 6: Reattach the Blade

Take the straightened blade, wrench and socket, flip the lawnmower up on its side and reattach the lawnmower blade. when you think the lawnmower blade is on tighten it some more. its better to be safe then sorry when dealing with this kind of thing.if you enjoyed this or found it in anyway helpful please remember to vote for it.

please remember it be careful and use your best judgement.

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Комментарии и мнения владельцев

I have a couple of problems with my Honda petrol strimmer and each time I have dropped off the item, It was repaired very quickly at a reasonable cost.

I also bought a new Honda self propelled petrol mower and they did a price match with major online retailers.Plus they assembled the mower for free!!Overall I am a very satisfied customer.

  • Very cool. If I was shopping for a new mower I woulddefinitely try something like this. I used to have a Black and Decker electric one, but the cord was a pain. Then we got a self-propelled gas mower (I loatheit). The one divorce issue that’s weighed the most on my mind is not wanting tomow the lawn, so I am selling all of that type of equipment and paying a guy tomow every other week 😉

I would like to politely and constructively suggest that anyone who flips their gas lawnmower over and turns the nut holding the blade without first disconnecting the spark plug wire is pretty much begging to be relieved of a finger or two. On many machines just turning the blade 1/4 turn will START THE FREAKING MOWER. Too bad Sk8ty forgot to mention that.

thank you for mentioning that, i did not realize how easly you could start the mower

I don’t know what kind of blades you people have but the ones on both my push mower and my riding mower are much too hard to bend with a pair of vicegrips. I tried using a 36 pipe wrench and still could not get them to bend back into shape, also beating with a 4# sledge hamer against the anval didn’t work eitherl.

im sorry that this method did not work for you, you could try heating the blade up before you try to straighten it.

if the blade is that tough how did it become bent?

Straightening a bend such as this on a mower blade is extremely dangerous. There is a substantial possibility of creating an undetectable fatigue crack in the metal allowing the blade to fly apart due to centrifugal force. Magnafluxing is the only way to detect such a flaw and it is not practical for such a low value part.

Your grass is like Chuck Norris. I don’t think I’ve ever bent a blade!

no unfortunately my grass is not Chuck Norris, I bet the blade on a 2 piece of steal pipe that got from a fence repair

Having done this more than a few times as a groundskeeper, a real quick way to do this is to clamp the blade in a vice, hammer the edge back into shape, then sharpen using an angle grinder.

I did this pretty much every day for 4 months straight, never had a blade fail! Also, keep in mind that a blade should generally be sharpened every 8 hours of use.

thanks for the writing complement

I would have used a vice if I had one, and the same thing with a grinder, I found that by bending the blade mostly straight before hammering it, that I did not damage the end as much.

Nice write-up. I’ve bent a few blades before. One thing to note. if you tilt the lawn mower the wrong way. sometimes fuel or even oil gets on the spark plug and makes it hard to start. If that happens, pull the plug and use a wire brush to clean the electrode.

thanks for the suggesting where the spark plug is on my mower I have not had a problem with that.

Ok thanks for the suggestions I have not hade a problem with the blade being out of balance but I have had problems with getting the tilt right and having it toss the cut grass into the bag

An extra step you might include is checking the balance of the blade. Put a round screwdriver in the center hole and see if it balances. If one side keeps going down you should file it down a little until it will sit evenly. If the blade gets to far out of balance it will vibrate like crazy and destroy the crankshaft bearing. Sometimes when it hits something like a rock it will chip off a little bit of metal and that is why you should check it.

I have had trouble getting some of the mulching blades to straighten correctly. They have a twisted blade to start with and getting it back that way is a problem.

A piece of railroad rail makes a great anvil. A foot long section is about right. It weighs a lot and you can pound on it all day and not bother it.

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

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.

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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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.

EASILY Fix A Bent Crankshaft On An Engine

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.

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.

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.

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.

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?

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.

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.


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.

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!

How to Tell If Lawn Mower Crankshaft is Bent?

Trusted Source Lawn mower. Wikipedia A lawn mower (also known as mower, grass cutter or lawnmower) is a machine utilizing one or more revolving blades to cut a grass surface to an even height.

? You might have recently hit a bump or a rock, and it caused damage to the machine. That might have led to a bent crankshaft, which is a common issue with lawnmowers. The problem is that you have no idea how to fix it.

Before you resort to repairing the unit, it’s important to determine the issue. But how to tell if the lawnmower crankshaft is bent? That’s what we are trying to discover in this article.

You might suspect something is wrong because your machine doesn’t act the same as before. For example, it might be vibrating while starting or during an operation, or you hear loud noises. The problem is that a bent crankshaft can lead to a variety of issues that could destroy your machine but also cause injuries. Here is what you should know about this damage and how to repair it quickly!

Can you find any signs of deformation?

Is there a way to positively identify that a bent crankshaft is causing problems with your machine? You have two approaches to determining the issue. The first one is to look for potential symptoms, and the alternative is to check the crankshaft yourself. Here is a detailed explanation of the lawnmower bent crankshaft symptoms.

Typical symptoms

The problems you can notice come down to the following:

  • Unusual sounds and vibrations – it’s normal for lawnmowers to emit some vibration and sounds. The problem is when the sounds are unusual and not the same ones as before. For example, the machine might produce harsh sounds once turned on, but only for a couple of seconds. It might vibrate excessively when you are trying to move it. Anything that seems out of the ordinary can be an indicator of a bent crankshaft.
  • Transmission problems – these occur when you try to ignite the lawnmower. It’s similar to starting a car – you might have trouble turning it on, and it could require several tries to succeed. It’s a common symptom of a bent crankshaft.

Physical inspection

The next is a physical inspection, which means checking the crankshaft by yourself. Now, there are multiple ways to do this, and we’ll explain them below.

While you are assessing the unit, you might encounter other issues, too. If you have a problem with your blades, find a replacement among the best lawn mower blades to ensure the maximum longevity of the new component.

How does it work?

If you want to determine a bent crankshaft, it’s best to ask a neighbor or family member to help with assessing the damage. For starters, take off the spark plug from the machine. Now, ask the other person to initiate the cord to start the machine. While they do that, you FOCUS on the blade and the bolt that holds it. If you notice any shakes or wobbles, it’s an indicator something is wrong.

Now, there is another method on how to perform a physical inspection yourself. Here are the steps to follow:

How to Tell if if Your Lawnmower Blade or Engine Crankshaft is Bent / How to Properly Tip the Mower

  • Remove the spark plug and turn your machine over.
  • Identify the cutting deck skirt on one end. Use a ruler and clamp it from the deck’s edge to the place where the shaft touches it.
  • Use your hands to turn the shaft. Check out the gap and see what happens during a single rotation. Did it expand and contract after that? If that’s the case, there’s a deformity in your crankshaft.

To avoid these issues in the future, you can also get an electric model, such as the Greenworks G-MAX 25322. It can mow 400m2 on a single charge and is suitable for various grass types.

What causes a bent crankshaft?

Your mower’s blade operates at over 200mph when in action. Those are huge speeds, which is why the machine uses plenty of kinetic energy. Once the unit encounters an obstacle, such as a blade, it dissipates energy through the shaft and the blade. It’s that energy that causes the bending.

Here are some causes of a bent crankshaft:

  • You hit a rock, sprinkler, pipe, or another immovable object that’s not too light.
  • You tried to do something with the machine and dropped the shaft accidentally.
  • Something went wrong during the manufacturing, installation, or maintenance process.

It’s always Smart to pick reliable and high-quality mowers to reduce the risk of any issues. The selection of the best corded electric lawn mowers can help to identify the right machine in that category.

How can I repair a bent crankshaft?

The first thing is to secure the right tools.

Here is what you’ll require:

lawn, mower, shaft, bent, remove
  • Wrench
  • Screwdriver
  • Nut drivers (depends on the machine)
  • Socket set
  • Heavy pipe
  • Valve spring compressor tool
  • Rubber hammers
  • Vise grips

The first step is assessing the shaft. Here are the steps for doing that:

  • Make sure your lawnmower is cool and turned off. Make sure to drain the oil by removing the oil plug. Now, drain the fuel by disconnecting the hose and opening the gas cap.
  • Remove the air filter and then take off the engine. You want to remove the oil tubes and throttle cables, too.
  • Now, take off the clutch, but use a wooden piece to place between the housing and the flywheel.
  • Pry loose the flywheel bolt and remove the shear pin from the shaft. Remove the bolt from the blade, too, and take off the bolts that hold the engine and the deck.
  • Place the motor in a safe position and use a screwdriver for the screws that keep the valve spring cover. Use the compressor tool to push down the spring. Allow it to compress and then slowly let go. Now, do the same with the other valve.
  • Check out the blade and find the camshaft gear. Remove it and unscrew the bolts to access and disconnect the rod end cap.
  • Slowly turn the crankshaft and take it off the engine.

Now, let’s do the straightening process. Position the shaft on a solid surface and place a heavy pipe on top of the bent. Use a hammer over the pipe several times. Now, see if the shaft is straight by using a level. If necessary, do some more straightening with the pipe and the hammer.

Once everything is straight again, assemble the machine back. You can follow the same steps above but in reverse. If you did everything right, the machine should work correctly again.

Trusted Source Buying a lawnmower: a guide | Family finances | The Guardian Whatever the size of your green sward, it’s time to consider how you are going to keep it under control.

? Check the CRAFTSMAN M105 lawnmower, an affordable battery-powered unit that’s an excellent choice for residential landscapes. The maneuvering process is easy with the bigger rear wheels, and you can pick from five different cutting heights.

Extra tips

Here are some other crucial things to note when dealing with a damaged crankshaft:

  • Check the warranty – is your product still under warranty? If the answer is yes, you’ll need to find a licensed technician. If you try to repair the issue yourself, it will void the warranty. If it happens that you fail during the repair, you will have to pay someone to fix the unit.
  • Is the repair worth it? – although fixing a bent crankshaft doesn’t have to be expensive, replacing this part is. If the replacement is necessary, make sure that’s the right move. Perhaps it’s better to check out the best lawn mowers under 400 and invest in a new unit.
  • Pay attention while mowing – the reason why the crankshaft gets bent is that it hits an obstacle. It’s impossible to notice every rock, but paying attention while mowing might decrease the risk of bending it.


Q: What’s the price of replacing a bent crankshaft?

A: The total price shouldn’t go over 100. If you decide to pay a professional to handle the repair, that could increase the cost to 150.

Q: Is it possible to continue using the lawnmower when the crankshaft is bent?

A: While it might theoretically be possible to use the machine, the experts advise stopping immediately. If you notice any issue with the crankshaft, it’s imperative to stop it from damaging the engine and destroying the unit. It’s easier and more affordable to fix a bent crankshaft than a damaged engine.

Q: Is it Smart to fix a bent crankshaft by yourself?

A: You should only do this if you know what you’re doing. If you are unsure about any step of the process, call a professional. It helps if they are a licensed agent for that mower brand. Another thing to consider is the warranty – if it’s active, you shouldn’t handle the repair yourself.

Final thoughts

A lawnmower is an incredibly useful machine. It makes maintaining residential and commercial landscapes easy. While using these devices isn’t challenging, it’s vital to recognize any problem as soon as it appears. A bent crankshaft is a common issue with mowers, so pay attention and make sure to recognize the signs.

We hope our guide helped with how to tell if the lawnmower crankshaft is bent. You should rely on your eyes and ears when determining the issue. Once you establish the bending of the crankshaft, you have the option to repair it yourself. However, make sure that you know what you are doing during each step. You don’t want to risk causing even bigger damage. If you feel like you could use help, don’t hesitate to contact a professional.


A lawn mower (also known as mower, grass cutter or lawnmower) is a machine utilizing one or more revolving blades to cut a grass surface to an even height.

Whatever the size of your green sward, it’s time to consider how you are going to keep it under control.

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