Why Your Toro Mower Belt Keeps Coming Off or Breaking


If you own a Toro lawn mower, chances are you have had a belt come off your mower and wondered why. If you have a belt that won’t stay on your lawn mower or mower deck you need to check over your lawn mower to make sure your belts are in good condition and there isn’t damage to other parts of your lawn mower.

Toro drive belts and mower deck belts are a necessary function to your mower. If the one of the belts falls off your lawn mower, your mower will fail to move or fail to cut. It’s important to keep your belts, pulleys and brackets in good shape. Read more about the different types of belts.

Keep your Toro lawn mower belt from breaking or coming off by adjusting belt guides and brackets; removing debris from pulleys and tensioners; and replacing damaged brackets, bearings and bushings. Replace loose, oil covered or cracked belts.

Before you begin working on your Toro mower, make sure to remove the spark plug for safety reasons. Let us explain why your belt may come off your mower.

Find Toro mower belts at your local Toro dealer or online at Amazon.

Lawn mower belt snapped

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8 Reasons Why Your Toro Mower Belt Keeps Coming Off or Breaking

1. Toro Belt Guide Damage

The belt guides, or sometimes called belt keepers, are small rod-shaped posts that go around the pulleys. On some lawn mowers belt guides travel alongside the belts depending on how long the belt must travel.

Belt guides can move out of place or become bent when a belt snaps or the belt has a lot of slack in it. The extra slack can cause the belt to hit the guide and bend the belt guide back toward the pulleys sometimes causing the belt to jump off the pulley.

Keep in mind, belt guides should never touch the belt. Instead, they should be very close to the belt remaining 1/8″ to 1/4″ away from the pulley. Brackets can be adjusted by hitting them with a small hammer or using a vice grip to move the brackets back into place.

2. Loose Toro Belt

Inspect your belt to check if it seems loose. This can be a sign it is time to replace it. I like to replace my mower belts at the same time because if one is pretty worn or stretched from normal use; the other is probably due to be changed.

3. Shredded Toro Belt

If you find your Toro deck belt or drive belt is shredded, most likely the belt is rubbing on a bracket or a belt guide. It also may not be tracking correctly. Look at the components that are near the belt to see what the belt has been rubbing against.

A shiny spot on a bracket or belt guide is an indication that the belt is rubbing against this area.

Once you isolate the items causing the shredded belt, adjust the bracket or belt guide back in place so it no longer rubs against the belt. Check bushings in the brackets on your Toro to make sure they are not bad. Some brackets have replaceable bushings while others do not result in the whole bracket needing replacement.

4. Damaged Bearings in Pulleys or Cutter Housings

Next, look at the pulleys that the belt rides on. If any of them are not running flat and straight, a bearing in the pulley can be bad. Most of the time, you will find the bearing that fails is located in an idler pulley.

The idler pulley has a sealed bearing in it so you will have to replace the whole pulley if you find a bad bearing. Not every pulley will have a sealed bearing. You may find the drive pulleys or spindle housings will have replaceable bearings so you are able to complete repairs with fewer parts.

You can find bearing failures in spindle housings by grabbing a hold of the blades and rocking back and forth. If you feel movement, the bearings in the cutter housings or a complete cutter housing needs to be replaced. Toro spindles that are making noise and excessively vibrate can cause your belt to come off from the mower deck.

5. Debris in Grooves of Pulleys on Your Toro Mower

Look at the grooves in the pulley and check for rocks, wood chips and other debris that may get caught in the pulleys. There have been times where we have found debris and even dried mud caked in the grooves of the pulley.

A Toro mower belt can break because debris caught in the deck and under the pulleys. The belt is unable to stretch around the additional debris. The stress of being stretched can cause the belt to break Belts don’t always break because they are old. Many times, new belts snap because a foreign material is caught in the pulleys.

6. Idler Tensioner Bracket or Spring is Worn

The brackets that hold the idler pulleys in line usually have a spring on one side and a pulley on the other. If the hole where the spring attaches is worn or the spring is worn, a constant vibration is created.

The bushing on the idler bracket can also become worn out if it isn’t greased. This can result in the pulley running on an angle. The pulley can cut into the deck or the bottom side of the mower if it is a transmission belt. This vibration along with the pulley running on an angle can throw the belt off the mower.

7. Debris Interfering with Proper Tension on Belt

The deck needs to be kept clean of debris. Dry grass and debris can collect under the lawn mower or on the deck which can cause the tension pulley not to move properly. The tension pulley on a Toro mower is no longer able to keep proper tension on the belt. If the tensioner can’t move, then the belt can’t stay tight.

This is one of the reasons it is very important to keep your lawn mower clean under the belt covers and under the mower body. Also, the cleaner you keep your lawn mower, the easier it is to find parts that may be failing before they fail.

Check out our articles, “How to Clean Your Lawn Mower for Best Performance” and ” How to Find & Prevent Substantial Lawn Mower Deck Problems ” to learn more on how to keep your mower clean and in good condition to extend your mower’s lifespan.

8. Oil or Rust on the Belt

An oil leak on your Toro lawn mower may collect on the belt. This is another problem that can cause the belt to come off. The pulleys need to be clean of oil and rust to keep your belts in good shape. Oil is a petroleum product that will make the belt swell if the belt remains in oil for a long time.

An oil covered belt will also begin to ship on the pulleys and cause the belt to not be able to grab and just build heat.

Rust will cause the belt to dry out and crack. If your belts have any types of cracks in them the belts need to be replaced as soon as possible.

Related Items

How Long Do Toro Mower Belts Last

Lawn mower belts can be pretty pricey depending on the manufacturer and type of mower you are running. Drive belts and deck belts are two of the most common lawn mower belts. Belts can cost anywhere from $20 to $200.

I recommend purchasing an OEM belt from the manufacturer of your lawn mower. You can probably find a cheaper belt online or have a local auto parts store try to match the belt for you, but they rarely last as long or perform as well as an OEM belt.

I go into more depth with my article, “This is How Long a Mower Drive Belt Should Last“.

You can also find out more information on belts in “V-Belts: What Are They?”

My top items to keep on hand to service & troubleshoot your lawn mower

Socket & Allen Wrench SetOpens in a new tab. – Tool set needed to service & troubleshoot your mower problemsCarburetor CleanerOpens in a new tab. – Clean clogs & buildup in fuel system
MultimeterOpens in a new tab. – To check voltage, continuity & current to identify electrical problemsFuel StabilizerOpens in a new tab. – Stabilize & clean your fuel to minimize fuel system buildup
12-Volt Battery ChargerOpens in a new tab. – Battery/trickle charger to start your mower & slowly charge your batteryFilter WrenchOpens in a new tab. – Helps loosen your filter
Oil Drain PanOpens in a new tab. – To collect oil with spout to place in containers for disposalBattery Powered InflatorOpens in a new tab. – Keep your lawn mower tires inflated to prevent uneven cutting or steering issues

Powered Equipment Team

We're just a guy and a girl obsessed with outdoor power equipment! We are excited to share the knowledge and tips we have learned over our combined 55 years in the power equipment industry. We have both ran equipment dealerships and took pleasure in helping our customers everyday providing equipment repair, parts, purchasing, and business tips to our residential and commercial clients. We hope our blog will help you with your next purchase, repair, or project.

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