How to Fix a Self-Propelled Lawn Mower

If your self-propelled lawn mower has suddenly become a push mower, if it runs rough, or if it won’t even start, don’t panic. You might not need to take it in for service yet. Use these quick tips to narrow down the problem and fix it. Many of these solutions will work no matter if you have a gas, electric, or cordless model.

Here are the three most common dilemmas facing the owners of self-propelled lawn mowers.

1.    The mower doesn’t self-propel anymore, or it moves too slowly

 

This usually results from a problem with the cable that controls the speed. It’s probably the most common complaint about older self-propelled mowers.

Transmission cable

Time to complete: less than 10 minutes

Image courtesy of Toro.com

If the transmission or drive cable comes loose or breaks, your mower will stop moving forward on its own. Inspect the whole cable from the handlebar down to the transmission. Make sure it’s connected firmly at both ends and doesn’t need to be replaced because of wear or damage. (Rodents love to gnaw on wires, especially plastic-coated ones. If you have uninvited guests in your garage over the winter, you might have a few gaps in your cable.)

 

If you have a Personal Pace mower and it’s moving too slowly, check the wire cable that runs from the handle down to the transmission. With the engine turned off, squeeze the Personal Pace handle. It should move about an inch before you feel resistance. If it moves more than that, the cable may need tightening. This tends to stretch with wear just like a gear cable on an old ten-speed bike.

 

Loosen the bolt that clamps the cable onto the handle. Pull up the drive cable about an inch, tighten the bolt, and then squeeze the handle again. If there is less play, test the mower’s speed with the engine running.

Wheels and the drive wheel gears

Time to complete: less than 10 minutes if you don’t have to remove the wheels

Wheels and gears need cleaning and lubrication, and sometimes they just need to be replaced. Your mower will move much more slowly if the drive wheels and gears are jammed up with clippings and dirt. Clean them and spray them with WD-40 or graphite.

 

2.    The mower vibrates too much, makes noises, or cuts poorly

If you have a bent, damaged, or unbalanced blade, it will make the mower shake more than normal. It will also damage your lawn by tearing out grass or making ragged cuts. If you can’t see the ragged cuts now, you will soon enough, as the grass will turn brown at the tips.

Please remember to disconnect the spark plug cable before doing any of the maintenance described below.

Blade

Clear out grass clippings and dirt from the underside of the mower. If the blade is obviously bent or damaged, replace it. If it looks okay, but you’re still getting bad vibrations, remove it. Check the balance by using a balancer or hanging it with a nail through its center hole. If one side hangs lower, file that edge until the blade hangs level. Sharpen the blade about every two weeks for the best cut.

Motor shaft

Once you’ve removed the blade, you can see the rod, or shaft, connecting the blade to the motor. If you’ve run over large rocks or tree stumps, it may be bent. If it is damaged, we recommend that you take the mower to a mechanic.

3.    The mower runs rough, or won’t start

Just like in a car, a bad spark plug, drained battery, or stale fuel can stop a mower from starting. If your mower has a fuel shut-off valve and it’s closed, that could prevent your mower from starting, too. Make sure any safety features (like blade control) that keep the mower from operating are all disengaged. Then try starting the mower again. If that fails, try the steps below.

Fuel

If you’ve left gas in the tank all winter without using a stabilizer, the gas may have gone bad. Does it smell wrong? Remove all the fuel, change the filter, and then put fresh gasoline in the tank. (At least with self-propelled 4-cylinder engines you don’t have to mix the gas and oil together.)

Spark plug

Time to complete: less than 5 minutes

Disconnect the spark plug cable (but wait, you already did that, didn’t you? Safety first!), pull out the spark plug, and wipe it clean. If the porcelain is cracked or the electrode burned off, you’ll need a new one. Lawn mower spark plugs need to be replaced about once a year. After you put it back, or put in a new one, connect the cable. Does the mower start?

 

Battery

If your mower has electric starter that runs off a battery, see if the battery has drained. Recharge it, or replace it if it won’t hold a charge. Do the same for cordless mowers that run off batteries.

Cord

Electric mowers are dependent on extension cords, and those cords are prone to damage. Try a different cord and test the outlet to make sure it’s working.

Carburetor and Air Filter

Clean, or better yet, replace the air filter if it’s filthy. Cleaning a carburetor is a big job, but it’s not impossible. See if your mower’s manufacturer gives advice on how to do it, or else take your mower to a mechanic.

If all else fails…

If your mower is out of warranty and repairs are too expensive, consider getting a new self-propelled lawn mower. See the reviews of the latest and greatest models. Find out what features will make your mowing easier. Read more at lawntoolsguide.com.

 

 

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