Your Honda push mower is always going to have a little vibration when the engine is running. However, the vibration may feel more intense when parts of the mower begin to wear or become damaged. Mowing in this condition can make you feel like a vibrating windup toy pushing a mower.
A Honda push mower may vibrate when the engine mounting bolts are worn; the engagement lever is loose; the blade adapter is broken; the mower blade is bent or unbalanced; the crankshaft is bent; the flywheel key is sheared, or hardware is missing or loose.
Take all safety precautions when working with your mower. This includes removing the spark plug to prevent the mower from starting and protecting your hands from the sharp edges on your blades.
Refer to your owner’s manual for all safety precautions to take for your mower model.
Reasons Your Honda Lawn Mower is Vibrating
Engine Mounting Bolts
If you experience a vibration when you engage your mower blade, check the mounting bolts under your engine.
These mounting bolts, also known as motor mounts, are installed to absorb vibration from the engine. Secure any loose bolts and replace broken or missing mounting bolts.
Engagement Lever
Your Honda push mower uses a lever to engage the blade. This lever needs to be checked for loose or worn components that can cause a vibration. Tighten the components and replace any parts showing signs of wearing.
Loose or Damaged Blade Adapter
The blade adapter can become damaged or fail when the blade has a significant impact to a stationary object or when it becomes weak following many smaller impacts.
It can also become worn when there is damage to the crankshaft, the wrong blade is used or the blade is unbalanced.
A broken blade adapter must be replaced along with a new Honda mower blade. Inspect the crankshaft for damage before installing the new adapter and blade.
Bent Mower Blade
A bent mower blade will cause vibration to be felt through the mower. This happens when the blade hits a solid object like a tree root or rock. To check for a bent blade, park your mower on a flat surface.
Measure from the ground to the blade tip. Rotate the blade 180 degrees and measure from the same spot on the ground to the blade tip. If there is more than a 1/8” variance between the two measurements, replace the mower blade.
Another way to determine whether you have a bent blade is by removing it and matching it to a new mower blade.
If they don’t fit together and there are gaps remaining between the old and new blades indicating the blade is bent, it must be replaced.
Never attempt to straighten a mower blade. The metal becomes compromised and can become weak. There is a possibility the blade will crack and fly out of your mower at very high speeds.
This can put people and objects in the area at risk of injury or damage.
Worn or Unbalanced Mower Blade
Wearing of the Honda mower blade is something that is unavoidable. Dirt that rotates under the mower deck can cause uneven wearing.
When the ends of the blade or blade sail (the high side of the blade) are thinner than the center of the blade, the blade needs to be replaced.
Not only can the blade become unbalanced from wearing unevenly, but it can also become unbalanced during the blade sharpening process. This happens when more metal is removed from one side of the blade than the other.
An unbalanced blade can make your blade wobble when it begins to rotate. At very high speeds, the wobbling can cause a significant vibration. Check the balance of your blade using a blade balancer.
If you don’t have one of these inexpensive tools, you can place a nail in the wall with the nail head about 1 inch away from the wall. Place the center hole of the blade onto the nail.
A balanced blade should sit level. If it doesn’t sit level, remove a little metal from the side of the blade that hangs lower until it sits level.
Bent Mower Crankshaft
A bent crankshaft will definitely cause your mower to shake. You can perform the following tests to determine whether the crankshaft is bent. Be careful and protect your hands from the sharp blade.
With your spark plug removed and a clamp holding the safety lever to the handle to disable the flywheel brake, carefully spin the blade and watch the center bolt. If the bolt is moving all over the place, your crankshaft is most likely bent.
If you are unsure about rotating the blade, remove the blade and blade adapter. Turn the crankshaft and measure to make sure the shaft is remaining in the center.
You can use a dial indicator or some form of a stationary object to gauge whether the crankshaft is moving off-center indicating it is bent.
If it does not remain centered and shifts to one side, the crankshaft is bent and it’s time to replace your lawn mower. Replacing the crankshaft is often more expensive than purchasing a new mower.
Some choose to try to bend the crankshaft back in place, but this poses a significant safety risk. I highly recommend purchasing a new lawn mower.
Sheared Flywheel Key
The key located between the flywheel and the crankshaft can become sheared and cause a vibration. Remove the nut off the top of the crankshaft to inspect the flywheel.
You will find a small key in the keyway. If it is damaged, it must be replaced.
Loose Hardware
Check for loose hardware and worn parts on your mower that can cause items on your mower to vibrate.
Common Honda Lawn Mower Problems & Solutions
There is a price that comes with homeownership including the upkeep of your lawn. You invested in a lawn mower to assist with your lawn care.
Lawn mowers, no matter what brand, are subject to breakdown and become troublesome as they age.
While regular routine maintenance of your mower can prolong major repairs, you will still encounter problems. To help you identify items that may be causing problems in your Honda mower, I have put together a hand reference guide: Common Honda Lawn Mower Problems & Solutions