The lawn mower blades won’t turn. With the engine running, there’s no action under the deck. Everything worked fine when you put the mower away after the last cut. But don’t worry as I’m going to share my guide to troubleshooting the causes of this issue to get you up and running again in no time.
Why Won’t My Lawn Mower Blade Turn (The Short Answer)
One of several mechanical faults has occurred. Like with any mechanical system, things are certainly going to go wrong. A belt that’s become jammed or a seized bearing can be a couple of the more common reasons why a lawn mower blade won’t turn.>
Check These 5 Things If Your Lawn Mower Blade Won’t Turn
Here are five potential causes you might come across when you discover that your lawn mower blade will not turn or the lawn mower blade is hard to turn by hand. I’ve encountered each of them at various points.
An Obstruction in the Deck
You will often find the lawn mower blade is hard to turn by hand because of an obstruction within the mower’s deck. This could be anything from a piece of rope to a big stick that got wedged in the last time you mowed. Take a look under the deck to rule out obstructions as a potential issue.
A Bent Blade
Unfortunately, blades sometimes become severely bent, preventing the blade from rotating properly. A bent lawn mower blade should be pretty obvious to see.
Incorrect Blade
Buying a new blade for your lawn mower can sometimes be confusing. Incorrect sizes and designs can get wedged in the deck and stop rotating. Inspect the underside of the lawn mower and check that the blade is, in fact, the correct one. It may be hitting the side of the deck and causing your problem.
Belt Trouble
Belts can cause several issues; some are easier to diagnose than others. A belt that has come off or was installed incorrectly can stop a blade from turning. Inspect the belt’s path to see if it is twisted, jammed, or snagged under a pulley.
Seized Bearing
Depending on your mower’s design, you may have several pulleys. These moving parts require regular maintenance. A seized bearing in a pulley will stop a blade dead in its tracks. Spinning the pulley when the belt is removed will determine its condition.
Fixing a Lawn Mower Blade That Won’t Turn
Now that you have diagnosed the cause of why your lawn mower blade won’t turn, let’s look at the solutions and tools you will need to get things working. Don’t worry; it doesn’t matter if your lawn mower is a Toro, a Craftsman, or any other brand, as the steps will be the same.
Checking for an Obstruction in the Deck
With your mower safely turned off, lift the deck and take a look. If you notice something, unplug the spark plug and tuck the connector out of the way first to avoid mishaps. Then reach under the deck and dislodge the intruder. If you need a little more force, I recommend propping up the deck so you can get both hands on the task. Just be careful that the mower isn’t going to fall.
If you have a ride-on mower or bigger, just lift the deck into its highest position and take a look. If you need to work under the deck, use a block to prevent the deck from falling. If you are one of the lucky ones with a mower jack, then just make sure you’re using it properly. A big Toro sure is heavy, and you can’t imagine the damage it would cause if it fell.
Tools required to clear an obstruction:
- Mower Deck Prop (Jack, Concrete Block, or Similar)
TIP: Double Check if the blade is loose or damaged.
Removing a Bent Blade
Just like you did when checking for obstructions, take a look under the deck. If you see the blade is bent against the deck structure, it will have to be removed.
Start by removing the spark plug, then secure the mower deck in a lifted position, ensuring it’s firm. Place a block of wood or blade locking device inside the deck to stop the blade from moving if it becomes loose. Remove the center bolt with your tool of choice, such as a socket, ratchet, or an electric version. Grab a new blade and reverse the process to get the new blade installed. I would recommend that you inspect the deck for any damage the bent blade may have caused. You might need to carry out a deck repair for any rust or holes.
Tools required to fix a bent blade:
- Mower Deck Prop (Jack, Concrete Block, or Similar).
- Wooden Block or Blade Locking Device.
- Socket & Ratchet or Electric Version.
- New Blade.
TIP: Lubricate the bolt before installing the blade for easy removal next time.
Checking for an Incorrect Blade
Here you can follow the same steps for removing a bent blade. The only difference this time is that you will need to install the correct type of blade and recycle the incorrect one.
TIP: Take your old blade with you when purchasing a new one.
Belt Trouble
If you’ve diagnosed you have belt trouble; you’ll have to approach it in two different ways depending on whether the belt is intact or has snapped/damaged. If it happens to be snapped or damaged, you’ll need a replacement in hand to be able to complete the repair. The first thing you must do before you start is to remove the spark plug, disengage any other starting mechanism, and secure the mower in the correct position for repair.
Begin by removing the belt guards if your particular lawn mower has them and gain access to the belt area. Once accessible, remove the belt entirely so that you can inspect it thoroughly. Double-check that there is no damage to the belt caused by it coming off; if there is, then, unfortunately, it will have to be replaced. If it’s snapped, you will replace it anyway.
Reroute your belt following the belt layout; this should be printed on the top side of the deck or in your owner’s manual. Position the last section of the belt beside the tensioner; this is the pulley with the spring attached.
Some tensioners have a socket attachment that allows you to use a ratchet, making it far easier to release the tension by pulling back the pulley. If you don’t have this option, I’ve found the best solution is to place a heavy nylon string around the end of the spring to release the tension. You can now set the belt over the pulley with the tension removed. Finish installing the belt by adding tension back.
Run your eye over the belt to make sure it’s seated correctly. While making any adjustments, you should be able to turn the blade and allow it to seat itself. Repeat the same steps on all the pulleys if you’re working on a large mower with multiple blades.
Tools required to fix intact or snapped/damaged belt:
- Screwdriver or socket for belt guard
- Long-handled socket or wrench for the tensioner
- New belt if required.
- Rope/nylon string
TIP: Apply a belt dressing to extend belt life & prevent slipping.
Replacing Seized Bearing
This is the biggest job of all! To replace a seized pulley, you’ll have to follow the same steps of removing and reinstalling a belt outlined above.
First, remove the belt and then remove the faulty pulley. Pulleys are usually bolted to the structure with 3 or 4 bolts. Remove the faulty pulley and install the new one using your wrench or ratchet set. If you find the old one is not easy to take off, follow these tips on how to remove a pulley that’s stuck. Next, check if the new pulley needs to be greased. You may find a grease nipple that allows you to add grease, which should already be full. Once you’re happy with the grease, you can complete the steps to install the belt.
Tools required to install a new pulley:
- Long-handled socket or wrench for the pulley bolts
- New pulley
- Grease
TIP: Add “greasing pulleys” to your maintenance tasks to prevent seizing in the future.
Leave a Reply