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Why Does My Lawn Mower Vibrate So Much? Find Out Here!

Written by William
Last Updated on February 25, 2021

Lawnmower Is Excessively Shaking - Our Troubleshooting Guide

Lawnmowers are by no means quiet, especially if your mowing over uneven bumpy ground, some shaking noise is to be expected from the engine as it is working hard to cut your lawn.

However, excessive vibration can be a sign of a problem with your mower. Your lawnmower might be vibrating too much because of the blades, valves, engine or crankshaft.

We have gone into further detail below about what could be causing this vibration in your mower and how to fix it so as you can be mowing your lawn in peace.

Common Problems That Cause Vibration In Lawnmowers

From unbalanced blades to a bent crankshaft, there can be many different problems occurring in a mower that could be causing excessive vibration.

You should always stop the engine of your mower immediately when it starts to vibrate as this could even cause the blade to fly off and become a safety hazard.

We have listed out the typical parts in your mower which could be causing these problems below so as you can troubleshoot your mower and get to the root of the problem.

Damage/Debris On The Cutting Blade

If you mow in an area with a lot of trees and stones then it could be damaged from the sheer impact of hitting a hard object, causing the mower to vibrate.

Debris such as clay or mud can additionally get stuck on to the blade, causing the extra weight to make vibration on one side of the mower as the blades to spin around.

This is due to the uneven balance which will cause the mower to shake and vibrate when in use.

Solution

Always check for sharp objects and debris that can damage or attach themselves to your mower before you start cutting your lawn.

If you find that your blade is damaged then you need to replace it straight away otherwise it may affect how other parts of your mower operates.

Debris, on the other hand, can be easily cleaned off with a hose or stick, this should stop the uneven weight which is causing the vibration while mowing.

The Blade Is Unbalanced

Hitting rocks or sharp objects while mowing can also chip or unbalance your blade, causing vibration while in use. Bad sharpening of the blade may also mean one side of the blade is balanced and the other is not.

An unbalanced blade is similar to a washing machine and will make a lot of noise if it is unstable, causing vibration.

Solution

Try balancing your blade and see if this fixes the issue, and also tighten it, because if the blade is loose this could be causing the machine to make noise.

You should also sharpen your blade evenly on each side.

You Need To Tune Your Engine

If your mower is not vibrating due to a damaged or unbalanced blade then it could be due to the engine needing tuning.

When the engine on your mower needs tuning it will likely run rough and vibrate.

Solution

Keep good maintenance on your mower and tune it often so you can avoid this issue. This will also stop it from getting worn down too quickly.

There Is a Damaged Crankshaft

If your mower has run into something hard or heavy then the crankshaft could be bent or damaged, causing the blade to spin unevenly.

A loose crankshaft or mount can also make your mower run with vibration, especially if they are not tight against the frame of your machine.

Avoid using your mower while your crankshaft is bent or unbalanced as it can cause further damage to your mower and become an even bigger issue.

Solution

If your blade is damaged by an external force then the crankshaft most likely is too, repairing the crankshaft of a mower is not easy and may need to be done by a professional.

Always replace the blade before replacing the crankshaft and make sure to check if other parts on your mower are okay too such as the spark plugs and valves.

Your Flywheel Is Damaged

As we already know, when your mower hits something unusual such as a stone or rock it can damage numerous parts of your mower and cause a vibration.

This includes the flywheel key on your mower. Your flywheel key acts as a shock absorber on your mower and helps keeps the crankshaft and the flywheel in one position your machine, when this is damaged it can cause vibration while you use your mower.

You should be able to see if your flywheel has suffered damage just by looking at it.

Solution

Don't use your mower while there is an issue with your flywheel and replace the part as soon as you can before trying to start your mower again.

Try Adjusting Your Valves

If you have checked everything above and the blades on your lawnmower are fine and not damaged then you might need to adjust the valves on your machine.

So if you have a flathead mower you may need a professional to adjust these for you. Valves in the wrong position can cause an annoying vibration.

Solution

For a regular mower, not a flathead mower, you can readjust the valves into the right position, if you have a flathead then you need a professional to help you do this so as you can stop your mower from vibrating excessively.

How To Stop Vibrations In Your Lawnmower

Now we have listed out the most common culprits which could be causing your mower to vibrate, we have listed out a summary about how to check these issues on a push mower and fix them.

  • Step one - Wait for your mower to cool down and see if the engine housing on your machine is loose. Tighten the nuts and bolts to make sure everything is secure.
  • Step two - Remove the spark plug from your mower and tip it over to prevent leaks, look for any debris which has attached itself to your lawnmower.
  • Step three - If your blade is bent, you can push it against a piece of a wooden block to straighten it up. Then remove the nut holding down the blade and lubricate it, take off the blade underneath the nut that we straightened.
  • Step four - Take off any debris and grass stuck to the frame then install a new blade on your mower by retightening the nut you lubricated and turning the mower back over.
  • Step five - Reattach the spark plug on your lawnmower and see if the mower has stopped vibrating.

Frequently Asked Questions About Lawnmowers Vibrating Too Much

What is a crankshaft?

A crankshaft is a bridge between the pistons and flywheel of your motor, the role of it is to crank the flywheel of your mower in a circular motion.

How often should I replace the blade on my mower?

You should replace your mower at least once every year or season depending on how much you use it, if you damage your blade then you might have to replace it before this point.

What signs should I look for when I need to sharpen my mowers blades?

Signs that your mowers blades may need sharpening are vibration obviously, torn not cut grass and missed patches of cutting when using your mower.

How do you tip a lawnmower?

You should tip your lawnmower with the carburettor and spark plug pointing up so as fuel cannot leak from this side.

When should I tune my mowers engine?

You should tune your mowers engine after every 50 hours of use or at least once a season to keep it in the best shape possible.

Final Words

Overall, if your lawnmower is vibrating too much then you should always check your blade and crankshaft first before looking at anything else.

These parts of your mower take the brunt of any sharp or hard objects from your lawn such as rocks, and when bent or unbalanced can cause your mower to shake.

Simply replace or re-straighten these parts on your mower and it should be working as good as new after!

About the author
Written by William
I have always had a passion for gardening and that with a background in selling lawn mowers for the past 10 years, I have become very knowledgeable in all types of gardening tools. The site TheBestMowers.co.uk was created as a hub where I can review and write about all of the tips around gardening.
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