Riding lawn mower pulley. Riding Mower Belt Keeps Coming Off: Reasons and Fixes

John Deere Belt Coming Off? Easily Fix It! L120, LA130, LA140 Riding Mowers

Riding Mower Belt Keeps Coming Off: Reasons and Fixes

If your riding mower belt keeps coming off every time you take it out for grass cutting, it might be indicative of a more serious problem. This is included in the list of most common problems with lawn tractor-type riding mowers.

Instead of wasting time putting the deck belt back each time, you need to uncover what is causing this frequent slippage to occur. This complete guide will discuss why a belt repeatedly keeps coming off and how to fix each cause.

  • Why Does Your Riding Mower Belt Keep Coming Off?
  • – The Belt is Damaged
  • – Belt is Full of Dirt
  • – A Shredded Belt Comes off Easily
  • – The Wrong Belt Has Been Installed
  • – An Oil Leak Might Cause It To Slip
  • – The Mower’s Pulleys Are Damaged
  • – The Bearings Are Damaged
  • – The Bracket Below the Pulleys Is Damaged
  • – The Belt Is Misaligned
  • – The Belt Is Stretched
  • – Replace a Damaged Belt
  • – Keep the Deck in Perfect Condition
  • – Get the Wrong Belt Replaced
  • – Replace Faulty Bearings
  • – Fix the Pulleys if They Are Damaged
  • – Weld a Split Belt Bracket
riding, lawn, mower, pulley

Why Does Your Riding Mower Belt Keep Coming Off?

Your riding mower belt keeps coming off because of several possible causes such as a damaged, dirty, or incorrectly installed belt. This problem can also be due to an oil leak, damaged mower pulleys, damaged bearings, or a misaligned or stretched out belt.

As you can see, there are several potential reasons why the mower belt keeps coming off every time you use a riding mower. Here are some other potential reasons to check out. It is important to diagnose the root problem first before planning on a solution.

– The Belt is Damaged

You can take only so much work from the belt of a riding lawn mower before it gives up. We appreciate it if you lend your precious mowers, like the cub cadet mower, to neighbors and friends.

However, the mower is more likely to be used improperly and its parts damaged. Once the belt is damaged, it struggles to stay on the belt keeper and tends to come off at the slightest inconvenience.

– Belt is Full of Dirt

Dirt will inevitably accumulate over the belt of the riding mower or under the pulleys as time passes. The belt and its pulleys are close to the ground and on the receiving end of debris as you ride the lawn mower across the lawn.

When the belt accumulates dust, grass clipping, wood chips, and stones, the pulley has a harder time moving across the mower deck. The result is that the belt keeps coming off repeatedly every time the mower is used.

That is why cleaning the mower and removing potentially hazardous solid objects from the ground before use is very important. It might surprise you, but something as trivial as dirt on the mower belt might damage it.

– A Shredded Belt Comes off Easily

Shredding is common among belt problems, especially if the mower is too old. This happens when the belt regularly rubs against the belt keeper or bracket. When the mower hits a particularly rough spot, the belts get a bit displaced, after which it keeps rubbing against the belt keeper more forcefully.

The segment of the belt that is shredding will appear shinier than the rest of the belt. There will also be shiny spots on the belt keeper and the bracket. See whether aligning the belt back in place helps with this problem. You might have to adjust the parts against which the belt keeps rubbing into.

The shredding mostly happens because of an out-of-place belt bracket. The bracket can be salvaged if its brushings are still intact. However, if the brushings have been damaged, the bracket will have to be replaced.

– The Wrong Belt Has Been Installed

You could have bought an incorrect belt when replacing your last mower belt with the current one. It is common to get the wrong belt type, which then fits poorly and keeps coming off. We see this problem happening more when people order their belts off the internet.

There could be many reasons you have ended up with the wrong belt for the mower. You may have been trying to save money and bought a cheap alternative for your branded John Deere, or the one you ordered may need to be bigger for your mower’s engine.

– An Oil Leak Might Cause It To Slip

If an oil leak occurs in your lawn mower, most spilled oil will fall over the rotating mower belt. The belt will naturally slip over the belt keeper or the pulleys repeatedly until the oil is cleaned and the leak stops.

Oil leakage from the fuel tank occurs either because it has been overfilled or improperly sealed. Sometimes the spill might occur because of damage to internal parts and will need a professional mechanic to fix it.

– The Mower’s Pulleys Are Damaged

When the pulleys need to be fixed, the belt will keep slipping off repeatedly. Two pulleys keep the belt of a riding mower running between them. These pulleys always need to be on the same level so that the belt stays in place.

Unfortunately, it is very common for one or both pulleys to become damaged over time. This creates an imbalanced surface for the belt from which it keeps sliding. To confirm that the pulleys are damaged, you must remove the belt first. Only then will you get a better look at the condition of the pulleys, along with what needs to be done to correct them.

– The Bearings Are Damaged

For most rider belts, such as the cub cadet mower, faulty bearings within its pulley apparatus might cause the belt to slip. Even if a single one of the bearings are damaged, this will cause the pulleys to become loose or uneven on either side of the belt.

Again, you will have to turn the mower off, disengage the spark plug and remove the deck to inspect the bearing; if you are not that experienced in the technical know-how, then it is best to refer to someone who is.

– The Bracket Below the Pulleys Is Damaged

Once you have checked the belt and the pulleys and found no problem, a less common culprit might be the idle tensioner bracket or the plates below the pulleys. To observe them, you must fully expose the deck by removing the belt.

Carefully inspect the bracket and the plates to see if they are bent, cracked, or have incurred any other damage. Remember that these are very sensitive parts, so when they get damaged, the balance of the pulleys becomes off and the belt gets removed every time.

– The Belt Is Misaligned

This is the easiest problem to fix when a mower deck belt keeps getting loose for no apparent reason. When you get your mower checked or do something to it by yourself, the belt might get accidentally misaligned.

Even if it is slightly out of place, it immediately comes off during use. This problem will immediately be fixed by getting a professional to align the belt on the pulleys. Make sure you do not attempt to disassemble or take apart your lawn mower unless you know exactly what you’re doing. Making a mistake can lead you to more costly repairs down the line.

riding, lawn, mower, pulley

– The Belt Is Stretched

Sometimes the belt stretches too much when used for a long time. We are talking about good-quality lawnmowers that have been used for several years. Again, you can only find this out once you have gained access to the deck and inspected both the belt and the pulleys extensively.

A stretched belt will be too large to stay in place with the required belt tension and will frequently become loose. A stretched belt cannot be prevented, and you will have to replace it with a new one.

What To Do if Your Riding Mower Belt Keeps Coming Off?

If your riding mower belt keeps coming off repeatedly, you first need to find out the cause and then fix that problem. Replace the belt and its bearings if they are damaged and make sure to repair the other parts that have been affected.

Other methods you can try include keeping the deck in perfect condition, fixing the pulleys if they have been damaged, and doing some welding if the belt bracket has been split.

– Replace a Damaged Belt

If the belt has been damaged from overuse or improper use, it will simply have to be replaced. Unfortunately, there is no process or way to repair or fix a damaged belt. Replacement belts are easily available in the market at various price ranges.

Our advice would be to steer clear of cheap ones because they only last so long. Instead, increase your budget and go for the slightly pricier OEM belt that will last longer. Cheap belts will usually break down much faster than those that are made with higher quality materials. Purchasing cheap belts might be more affordable for now, but it will cost you more in the long run.

– Keep the Deck in Perfect Condition

If the belts keep coming off and you notice dirt and dust accumulated on the mower deck, then this is your cue to clean it right then and there. For thorough cleaning, it is best to remove the blade first. This way, you will have unrestricted access to the entirety of the deck for cleaning.

Whether you make your cleaning solution using soap and water or buy one from the market is totally up to you. First, use a metal putty knife or a wire brush to scrape off the dirt that seems strongly stuck to the surfaces. Then use a hose with the cleaning solution to clean the deck. You can also keep the blade on while cleaning the deck and use a long-handled brush to reach the corners.

It might seem like a hassle, but you must clean the lawn mower’s deck after every use. This can be accomplished within five minutes and will prevent dust from sticking stubbornly on the belt.

– Get the Wrong Belt Replaced

It isn’t very pleasant to buy a mower deck twice if you made an honest mistake the first time. See if you can exchange the wrong one with the new one to save a few bucks. This time, make sure only to buy the right size and best-quality belt from an authentic seller. It helps if you have a trusted mechanic or hardware store owner who can give you professional advice in this case.

– Replace Faulty Bearings

Once it has been established that the fault lies in damaged bearings within the pulley apparatus, you will have to replace it. If your mower has an idler type of sealed pulley, the whole pulley will have to be replaced due to a faulty bearing. In case of an unsealed pulley, you can replace the bearing and keep the pulley.

– Fix the Pulleys if They Are Damaged

Before you get to fix the pulleys, you have to remove the belt first. Start by removing both the right and the left side covers of the belt. The spring connecting the pulleys to the PTO needs to be removed next. After this, you can easily remove the mower belt and inspect the pulleys.

In a lot of cases, what happens is that the pulleys get bent after bumping into hard objects on the ground. Try to bend them back into shape and see that both pulleys are on the same level.

Sometimes, the pulleys are so damaged that nothing can fix them; in that case, replacing them is going to be the only option. This time, go for idler pulleys because they are better at keeping the belt in place.

– Weld a Split Belt Bracket

It is common to see the belt’s bracket split into two parts upon inspection. In most cases, this happens when the mower hits a particularly hard spot on the ground or a stone accidentally enters the deck.

Don’t worry because a split bracket can easily be welded back together. Because most of us do not keep a welding torch at home, a mechanic nearby can help you do this job better.


In the upcoming section, let us conclude this extensive guide on the reasons behind a loose lawn mower belt. Make sure that your safety is always the first priority — wear protective clothing such as safety goggles and long sleeved shirts when working on machinery like this.

  • It is only natural that the belt will become loose over time from prolonged mower use and will have to be replaced by a new one.
  • See if the pulleys are misaligned or have faulty bearings, which also cause belt slippage. While faulty pulleys can be fixed easily, faulty bearings will most definitely have to be replaced.
  • Sometimes the belt keeps coming off because of oil slippage or a misaligned belt, which have to be fixed as soon as possible.
  • Other times, even accumulation of dirt on the deck or the belt causes the belt to split repeatedly.
  • Make sure to keep the lawn mower’s deck in perfect condition to prevent dust from sticking to the belt.

As someone who is seriously invested in lawn care, you will eventually have to deal with a slipping mower belt sooner or later. Our extensive guide discusses all the reasons why this might happen and helps you fix the problem immediately.

The Best Zero-Turn Mowers of 2023

These achieve the rare feat of making lawn mowing fun.

By Roy Berendsohn Published: Mar 1, 2023

When it comes to yard work, zero turn mowers do the impossible. They make lawn mowing fun. They accomplish this by putting unprecedented speed, control and maneuverability at the disposal of the person mowing the lawn. The so-called “zero turn” feature of these mowers converts a grass cutting machine into something akin to an amusement park ride. You steer the machine with two levers—the left lever controls the left wheel, the right lever the right wheel. With that steering setup, you can zoom over the landscape cutting straight lines, curves, or pivot the mower into and out of a corner. What’s not to like?

Deck belt keeps coming off. 2 common reasons on John Deere 100 series riding mowers.

Read on to understand how these agile grass cutters work, how we go about testing them, and see some candidates that we’ve recently tested as well as some that we haven’t but that we think look particularly promising.

How Zero-Turn Mowers Work

A zero-turn riding mower consists of an operator platform, a frame and wheels, an engine (or battery bank), transmissions (or motors), and a pair of control levers commonly known as lap bars. In gas mowers, the engine powers a pulley system. One group of pulleys drives the blades, another group powers a pair of transmissions–one at each rear wheel. When you move the lap bar forward or back, you are directing the transmission to go faster, slower, or even turn the opposite way. When one drive wheel turns clockwise and the other counter clockwise, the mower pivots. When the wheels rotate at different rates, the mower turns in an arc-shaped path. When the lap bars are in the neutral position, the mower stops. Aside from a parking brake, there’s no other braking mechanism. Battery-powered zero-turn mowers work the same way, but have separate motors to drive the rear wheels and one for each blade inside the mower deck.

When it comes to transmission, most mowers have a Hydrogear EZT—a well-known and cost-effective residential-grade transaxle with a reputation for durability.

Some mowers use a deck stamped from one piece of steel, others use a deck fabricated from multiple pieces and welded together. A fabricated deck can be built from thicker steel at a lower cost than it would be able to be built otherwise. Once you’re talking about stamping metal as thick as 10 gauge (about 1⁄8 inch thick), the cost of stamping such a deck would push up the mower’s price beyond what most people are willing to pay. The decks in the mowers below range from 42 to 52 inches, a typical size in this class of product. When powered by these engines and the Hydrogear, these mowers will deliver a decent cut quality at their rated top speed of 7 mph. Note, however, that cut quality declines steeply if you maintain that speed in very thick grass or on uneven terrain.

As to the electric mowers, they represent the leading edge of the technology in this category. These are remarkable and expensive mowers powered by large-voltage lithium-ion batteries. If you’re interested in reducing mowing noise and simplifying your maintenance routine by eliminating gas and oil, they’re worth a look.

Selecting a Zero-Turn Mower

Everyone would like to select the biggest possible zero-turn mower with the hope of whittling a big grass cutting job down to size as quickly as possible. Reality usually intercedes because these machines are expensive and the wide range of options available today quickly drive up the cost. Roughly speaking, you start somewhere in the range of a mower with a 42-inch deck costing in the vicinity of 3200 to 3500 and move up in increments of 1000 to 1500 until you reach entry-level commercial-grade equipment that costs 7000 to 8000.

Again, speaking in terms of approximation, a mower with a 42-inch deck will cut a two-acre lot (that takes into account that the house, driveway, outbuildings and various landscape features are taking up some of that space). Use a mower with a larger deck to cut anything over two acres. But here’s the caveat. That entry-level ZTR mower (3200, say) with a 42-inch deck will wear out faster and need more maintenance than a mower with a 50-inch deck, a heavier frame, larger engine and higher quality transmissions, and thicker deck with more robust blade spindles, costing 4500.

In the simplest possible terms, you can cut a smaller area with a larger mower and expect more longevity out of the machine (not to mention a nicer mowing experience) or you can cut a larger area with a smaller machine and encounter more maintenance and a mowing experience that will be, we might say, a bit more rugged.

But there are still other factors to consider, in selecting a mower other than deck size and your budget. Larger mowers take more space in a garage or outbuilding. And a mower with a 50-inch or even 60-inch deck, as useful as it might be in getting the job done more quickly, may not fit through a fence’s gate, and it might be more difficult to maneuver in tight spots without creating scalp marks on the lawn from a lot of close-quarter pivoting.

riding, lawn, mower, pulley

Carefully consider all these factors when shopping for a mower: your budget, maintenance and whether you will perform that work yourself, mowing speed and time, maneuverability and trimming in tight areas, the importance that you place on your comfort while mowing, cut quality, longevity, storage, and access to the landscape.

How We Select and Test

There’s only one way to test a mower, and that’s to cut grass with it. But we also do more than mow.

We raise and lower the deck and adjust the seat. We look at service point access (the air filter, the spark plug, and the oil filter) and how easy it is to remove the deck. We mow approximately an acre with each mower, considering cut and mulching quality while running uphill, downhill, across washboard, and along sidehills. (On sidehills, we’ll mow surfaces pitched up to approximately 20 degrees; manufacturers generally recommend not going steeper than 10 degrees, but we like to be thorough.) We evaluate power and speed relative to cut quality—we investigate whether the mower delivers a decent cut mowing at full speed. When mowing in damp conditions, we look at whether the mower’s tires accumulate grass and how effectively it discharges moist clippings. Finally, we test maneuverability (these machines are, generally, very nimble) and how readily they come to a stop when you back off the lap bar control levers.