Ways to Fix a Lawn Mower that Vibrates Excessively
The reason why your lawn mower vibrates excessively is due to a faulty engine. If the engine is working correctly and your lawn mower still vibrates excessively, it could be a faulty, crankshaft or blade. The guide below should work with all top-selling brands, including Honda, RYOBI, Toro, Milwaukee, Troy-Bilt, DeWALT, and more.
Check the lawn mower engine
Some lawn mower blades vibrate after hitting an obstacle in the yard. It could be caused by the engine running rough or not starting. If the engine is not tuned up, it could cause the blades to vibrate excessively. If you want to increase the efficiency of your lawn mower, make sure that it is regularly tuned up. Doing this will allow it to run more efficiently and prevent it from getting damaged.
How to repair a lawn mower crankshaft?
Although the manufacturer of the vehicle’s engine may have a standard for the acceptable amount of damage to the crank, anything over.003 indicates the issue is severe.
Although it’s not recommended for a novice to fix a bent crankshaft, it can be done by yourself.
Through this way you can save a lot of money. However, to remove and replace the entire engine, you will need to tear it down. If you’re not ok with the idea of doing this on your own, you might want to consider asking a professional to perform a repair on your riding lawn mower. However, doing so will likely be more expensive than replacing the entire engine.
How to repair a lawn mower blade?
If you have a damaged or out-of-balance blade, it could cause severe vibration in your riding lawn equipment. At speeds of over 220 MPH, throwing the blade out of balance doesn’t take much damage, causing severe vibration.
There are several ways that a blade can get out of balance. If the blade gets struck by something solid, such as a tree root, metal post, pipe, or rock, it could cause it to break. This can lead to a chip or break-away part of the blade. If this happens, it should be inspected immediately.
A crack can also lead to a portion of the blade flying away from the machine. If the blade gets cracked or broken, it should be replaced immediately. Also, improper sharpening can cause the blade to become out of balance. When sharpening a blade, it’s important to remove the same amount of metal from both sides of the blade.
Doing so will cause it to become unbalanced. You will also need to test the balance of a blade when it’s being sharpened.
- You can do this by hanging it on a wall using a tool known as a hanging nail.
- The heavy side of the blade will eventually drop below the other.
- To maintain its balance, start sharpening the heavy side of the blade at a time until it evenly balances on the nail.
- Getting rid of and replacing a blade is easy, as long as it’s done properly.
- Before you can do this, you’ll need to tip the machine so that the carburetor is up.
- Depending on the version of the machine, you might need to remove some of the fuel from the tank before tipping the blade.
- You can remove the blade from its side using a pair of wrenches.
- If the screws are too tight, you might need to create a gap between the blade and the deck to prevent it from rotating.
- After removing the blade, you’ll need to clean the mounts and the washer.
- You’ll need to tighten the screws by hand to install the new blade.
- You can also use a torque wrench to finish the job.
There are a number of reasons, mechanical and otherwise, why a mower won’t run. The good news is that fixing most all of the issues is easy enough for a DIYer to handle.
By Tony Carrick and Manasa Reddigari | Updated Aug 8, 2022 4:03 PM
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Lawn care can be tedious, but once the grass starts growing in the spring, mowing becomes a fact of life in most neighborhoods. When you finally muster the strength to tackle that first cut of the season, there are few sounds as disheartening as that of a lawn mower engine that turns over but doesn’t start.
Before you drag the mower in for repairs or invest in costly replacement parts, first make sure that a clogged air filter, soiled spark plug, damaged safety cable, clogged mowing deck, or contaminated gas isn’t to blame. Work through the following steps, and you may be able to get your puttering grass guzzler up and running again in no time.
A lawn mower repair professional can help. Get free, no-commitment repair estimates from pros near you.
Change the lawn mower carburetor filter.
Your lawn mower’s air filter guards the carburetor and engine from debris like grass clippings and dirt. When the air filter becomes clogged or too dirty, it can prevent the engine from starting. To keep this from happening, replace paper filters—or clean or replace foam filters—after every 25 hours of engine use.
The process for removing the filter depends on whether you are operating a riding or walk-behind lawn mower. For a riding mower, turn off the engine and engage the parking brake; for a walk-behind mower, pull the spark plug wire from the plug. Then, lift the filter from its housing.
The only choice for paper filters is replacement. If you’re cleaning a foam filter, wash it in a solution of hot water and detergent to loosen grime. Allow it to dry completely, and then wipe fresh motor oil over the filter, replace it in its housing, and power up the mower—this time to the pleasant whirring of an engine in tip-top condition.
Check the spark plug.
Is your lawn mower still being stubborn? The culprit may be the spark plug, which is responsible for creating the spark that ignites the fuel in the engine. If it’s loosened, disconnected, or coated in water or carbon residue, the spark plug may be the cause of your machine’s malfunction.
Locate the spark plug, often found on the front of the mower, and disconnect the spark plug wire, revealing the plug beneath. Use a socket wrench to unscrew the spark plug and remove it.
Check the electrode and insulator. If you see buildup, spray brake cleaner onto the plug, and let it soak for several minutes before wiping it with a clean cloth. Reinstall the spark plug, first by hand, and then with a socket wrench for a final tightening. If the problem persists, consider changing the spark plug.
Clear the mower deck of debris.
The mower’s deck prevents grass clippings from showering into the air like confetti, but it also creates a place for them to collect. Grass clippings can clog the mower deck, especially while mowing a wet lawn, preventing the blade from turning.
If the starter rope seems stuck or is difficult to pull, then it’s probably due to a clogged deck. With the mower safely turned off, tip it over onto its side and examine the underbelly. If there are large clumps of cut grass caught between the blade and deck, use a trowel to scrape these clippings free. When the deck is clean again, set the mower back on its feet and start it up.
Clear the vent in the lawn mower fuel cap.
The mower started just fine, you’ve made the first few passes, then all of a sudden the mower quits. You pull the cord a few times, but the engine just sputters and dies. What’s happening? It could have something to do with the fuel cap. Most mowers have a vented fuel cap. This vent is intended to release pressure, allowing fuel to flow from the tank to the carburetor. Without the vent, the gas fumes inside the tank begin to build up, creating a vacuum that eventually becomes so strong that it stops the flow of fuel.
To find out if this is the problem, remove the gas cap to break the vacuum, then reattach it. The mower should start right up. But if the lawn mower won’t stay running and cuts off again after 10 minutes or so, you’ll need to get a new gas cap.
Clean and refill the lawn mower fuel tank.
An obvious—and often overlooked—reason your mower may not be starting is that the tank is empty or contains gas that is either old or contaminated with excess moisture and dirt. If your gas is more than a month old, use an oil siphon pump to drain it from the tank.
(It’s important to be careful as spilled oil can cause smoking, but there are other reasons this might happen. Read more about what to do when your lawn mower is smoking.)
Add fuel stabilizer to the tank.
Fill the tank with fresh fuel and a fuel stabilizer to extend the life of the gas and prevent future buildup. A clogged fuel filter is another possible reason for a lawn mower not to start. When the filter is clogged, the engine can’t access the gas that makes the system go. If your mower has a fuel filter (not all do), check to make sure it’s functioning properly.
First, remove the fuel line at the carburetor. Gas should flow out. If it doesn’t, confirm that the fuel shutoff valve isn’t accidentally closed. Then remove the fuel line that’s ahead of the fuel filter inlet. If gas runs out freely, there’s a problem with the fuel filter. Consult your owner’s manual for instructions on replacing the filter and reassembling the mower.
Inspect the safety release mechanism cable.
Your lawn mower’s reluctance to start may have nothing to do with the engine at all but rather with one of the mower’s safety features: the dead man’s control. This colorfully named safety bar must be held in place by the operator for the engine to start or run. When the bar is released, the engine stops. While this mechanism cuts down on the likelihood of horrific lawn mower accidents, it also can be the reason the mower won’t start.
The safety bar of a dead man’s control is attached to a metal cable that connects to the engine’s ignition coil, which is responsible for sending current to the spark plug. If your lawn mower’s engine won’t start, check to see if that cable is damaged or broken. If it is, you’ll need to replace it before the mower will start.
Fortunately, replacing a broken control cable is an easy job. You may, however, have to wait a few days to get the part. Jot down the serial number of your lawn mower, then head to the manufacturer’s website to order a new cable.
Check to see if the flywheel brake is fully engaged.
The flywheel helps to make the engine work smoothly through inertia. When it isn’t working properly, it will prevent the mower’s engine from working.
If it is fully engaged, it can make a mower’s pull cord hard to pull. Check the brake pad to see if it makes full contact with the flywheel and that there isn’t anything jamming the blade so the control lever can move freely.
If the flywheel brake’s key sheared, the mower may have run over something that got tangled in the blade. It is possible to replace a flywheel key, but it does require taking apart the mower.
Look out for signs that the mower needs professional repairs.
While repairing lawn mowers can be a DIY job, there are times when it can be best to ask a professional to help repair a lawn mower. If you’ve done all of the proper mower maintenance that is recommended by the manufacturer, and gone through all of the possible ways to fix the mower from the steps above, then it may be best to call a pro. Here are a few signs that indicate when a pro’s help is a good idea.
- You see black smoke. The engine will benefit from a technician’s evaluation, as it could be cracked or something else might be worn out.
- Excessive oil or gas usage. If you’ve changed the spark plugs, and done all of the other maintenance tasks, and the mower is consuming more than its usual amount of oil or gas, consult a professional for an evaluation.
- The lawn mower is making a knocking sound. When a lawn mower starts making a knocking sound, something could be bent or out of alignment. It may be tough to figure this out on your own, so a pro could help.
- A vibrating or shaking lawn mower can be a sign of a problem beyond a DIY fix. Usually something is loose or not aligning properly.
How to reduce vibrations in a push lawnmower
his article describes modifications to a walk-behind lawnmower to reduce vibration transmitted to the user’s hands. With a little mechanical modification, it’s possible to reduce the vibration to undetectable levels.
Vibration from hand-operated tools is a serious hazard. In the early stages it causes numbness and tingling in the hands that lasts for several hours. Over time it can become hand-arm vibration syndrome, which is an irreversible loss of sensation in the fingers, cold sensitivity, blanching, and hand tremor, sometimes known as secondary Raynaud’s syndrome. You can’t power through it. It’s essential to take precautions.
The injury is a function of (1) the amount of vibration, measured in units of acceleration, i.e. meters per second squared; (2) length of continuous time of exposure; (3) number of exposures; and (4) the amount of muscle contraction during use, which increases the efficiency of energy transfer to the hand. Even though a portable electric drill exposes you to 3–4 m/s 2. it’s less dangerous because few people will use a drill for two hours continuously. An electric pencil sharpener vibrates at 5 m/s 2. but even fewer people will sharpen a pencil for two hours straight while grasping an electric pencil sharpener. Those who need to do so are advised not to attempt the procedure below.
The frequency of vibration (and hence the amplitude) might also be a factor. Internal combustion engines vibrate at lower frequencies, though I know of no scientific studies comparing the effects of different frequencies.
Materials needed
| 2 | McMaster | 1555t121 |
| 1 pg | McMaster | 99620a585 |
| 1 | McMaster | 6527k414 |
| 1 | Lowe’s | |
| 1 | McMaster | 1370n18 |
| 1 pg | Hoe Depot | 0650889 |
| 1 Bx | Any | |
| 1 | Lowe’s | 1001 503 013 |
| 1 | ?? | |
| 1 | Any |
Hinge construction (view from top). Hinge is attached to the lower half of the handle (the mower side)
Construction
Before starting, try replacing the blade and spark plug on the lawnmower and check the drive shaft to make sure it’s not bent. Clean any dirt off the blade, as an unbalanced blade will cause vibration. Or try buying a newer model. If that’s not an option, the next option is to re-engineer the lawnmower as is done here.
How To Fix a Shaking Lawn Mower & Sharpen or Replace Blades
We will be replacing the screws that hold together the upper and lower halves of the handle with a rotating hinge. This will block any energy in the vertical direction. The hinge will also allow the upper half of the handle to move freely left and right, blocking most of the energy in the horizontal direction. So, we get rid of at least two thirds of the vibration.
I found in testing that a hinge is a better solution than trying to absorb it with rubber. In my initial tests, any rubber soft enough to absorb the vibration falls apart from the vibration after a few hours. I now have tiny bits of neoprene rubber all over my back yard. And, somewhere, a couple of ¼-20 hex nuts and a spring.
Procedure
Disassemble the handle at its midpoint. Cut two pieces of square tubing into U shapes and attach one to the outside of the lower handle on each side of the mower. Cut four sections of steel angle into L-shapes and attach them to the upper and lower sections of the handle as shown. These pieces limit the movement of the handle so you can still push it down to turn the lawnmower left and right. There is no steering mechanism on these babies.
Top: Floor mat. Middle: Throttle lever dampening. Bottom: Looks awful but it works
Bend the upper half of the handle to widen it so it rests inside the U, slap a couple of weak springs on the hardened steel rod, slap it together and secure the rod with retaining rings. Attach bits of the rubber mat where needed. Slap on some lithium grease and verify that the lawnmower still works.
The handle grip and throttle
Some vibration also comes up through the throttle lever, so remove it and mount it on L-shaped pieces of neoprene as shown in the picture. Make sure the throttle still opens to the normal position and closes when the handle is released.
Finally, use cable ties to attach pieces of the rubber mat to all the surfaces on the handle that your hands will contact, including the throttle handle and the clutch (if your mower has powered wheels). The mat should only go on those parts your hands will touch, not completely around the levers.
Results
Here are the results on a Sears 4-wheel drive push lawnmower. The modifications reduced the vibration by about 7 times as measured by a vibration meter. Even so, some vibrations were still detectable and I had to wear Ergodyne 9015F(x) vibration-reducing gloves to eliminate the vibration entirely.
At one point I tried attaching springs between the upper and lower sections to keep upper section suspended. It turned out not to be necessary, as the user automatically keeps the sections apart when pushing the mower. Springs also transmitted more vibration to the handle because they drew the two sections closer together, increasing friction on the shaft.
Vibrations measured at various points of a lawnmower. v=vertical, h=horizontal, f/b=forward and back.
I also tried adding weights to the upper half of the handle, thinking the added momentum would dampen the vibrations. It didn’t work: the weights increased the friction, making the vibration much worse. Keeping that friction as low as possible seems to be the critical thing.
In my part of the country, I have to cut the grass every week. It takes 1½ to 2 hours. Previously my hands would be tingling and numb for hours. Ominously, each time the tingling would get worse. After making these modifications, that no longer happens.
Now to do something about that pencil sharpener.
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