Lawn mower belt slipping. How Tight Should A Mower Deck Belt Be For Top Performance

How To Tighten Drive Belt On Cub Cadet?

A Cub Cadet drive belt needs to be tightened periodically so that it does not slip off the pulley. We have researched the proper DIY method for adjusting the drive belt tension, and here’s what we found.

Tighten the Cub Cadet drive belt by replacing the spring tensioner or trimming some segments of itt. The spring tensioner provides a certain amount of tension, allowing the belt to run smoothly. Over time, it can wear out and need replacing.

If a worn belt cuses loose tension you can adjust the brake link for a temporary fix. Replace the worn drive belt for a permanent fix.

Most people think that they need to replace the drive belt when they notice that the belt is slipping. This could be the case, but it’s just one side of the coin, and we’ll look into this. In addition, we’ll walk you through not only how to tighten the drive belt but when you should replace it. So keep reading below to learn more!

Why Is It Important To Check Drive Belt Tension In Cub Cadet?

When you mow your lawn, you’ll see the blades spin quickly to cut the grass. The drive belt, which connects the motor to the blades, spins around the pulleys and provides the necessary tension to rotate the blades.

However, in some cases, the belt tension is too loose. A loose drive belt can cause a lawnmower blade not to spin. If your Cub Cadet engine is running fine, but it is not moving forward, you could have a loose belt.

However, if it does run, yet skips and jumps when you try to cut grass, this is because the drive belt is not able to grip the pulley. To keep the belt in place, it’s crucial to know the proper tension. If you loosen the belt, you’ll reduce its effectiveness.

What Provides Tension To The Drive Belt?

There are two components of your Cub Cadet that provide tension to its drive belts: the spring tensioner and the drive belt itself.

The spring tensioner is a wearable part found in many Cub Cadet lawnmowers and is usually attached to one of the V-pulleys. The other component is the drive belt itself. A worn drive belt should be replaced if it shows signs of fraying.

How To Replace The Spring Tensioner To Tighten Cub Cadet?

If the spring tensioner of your lawnmower has lost its ability to hold the drive belt in place, it’s time to replace it. Below are the steps to follow when replacing your Cub Cadet spring tensioner:

Remove The Cutting Deck

You should see a small bracket that holds the deck belt in place in your front engine pulley. Determine the bolt size (usually 8 mm) and loosen it up using the right socket size power tool.

Once you have the bracket removed, slowly pull the deck pulley down. Check for bowtie clips within the deck frame and take them out. The deck frame should loosen up, and you should be able to move it away from the cutting deck.

You’ll see a bowtie clip and spring attached to the cutting deck. These two connect the deck to the blade engagement cable. Pry the spring and bowtie clip out so you can separate the deck from the cable.

The video below illustrates the process:

Turn Your Cub Cadet On The Side

Once you have the deck out, turn your cub cadet on the side, so you expose the underside and start working on replacing the spring tensioner.

Alternatively, you can also jack it up so you can get to the bottom of it. It’s much easier if you do it sideways though when replacing the drive belt.

Locate The Spring

You should be able to identify and locate the spring easily. Just look for the V-pulley with a spring.

Remove The Spring

The spring is attached to a bolt and a V-pulley. You can pry both ends of the spring loose using a cutter-type plier.

Attach The New Spring

Once you remove the old spring, you can put a new one in place. Be sure to use a replacement part that fits your model of Cub Cadet mower. A temporary fix would be to trim segments of the old spring and reuse the spring.

However, we don’t recommend this, as the spring has already been stretched out and has little remaining life in it. It’s just a matter of time before the spring loses tension again or worse, breaks because of corrosion.

Also, you might consider spraying anti-rust on the surface while working on replacing your spring tensioner or drive belt for an added layer of protection.

Follow The Steps In Reverse Order To Put The Parts Back

The last thing you want is to end up with a DIY project that turns out to be bigger and more complex than anticipated. It’s important to document everything you do when working on projects, especially when it is your first attempt.

You want to be able to refer back to your notes and photos to help you identify any missed steps.

Taking pictures and videos of the installation or replacement process helps you recall and visualize the exact steps you took to complete your project.

How To Replace The Drive Belt Of Your Cub Cadet?

One of the best ways to tell if a lawnmower’s drive belt needs replacing is by inspecting the condition of the drive belt itself. If you see any damage, rips, cracks, or cuts, then you know that it’s time to change it.

Pro tip: when replacing either the spring tensioner or drive belt, you might as well replace the two altogether to save you time in the future.

Here are the steps to replace your Cub Cadet drive belt:

Remove Cutting Deck

Follow steps 1 and 2 above.

Remove The Clutch

You will see a bolt that attaches the clutch of your Cub Cadet to the motor. Loosen the bolt and disconnect the connecter that connects the clutch to the motor. You should be able to remove the drive belt after doing this.

Put The New Drive Belt

Slip the belt into the transmission pulley and into the motor pulley first. Once you have it in there, start working your way until the belt is slipped into each of the pulleys.

The groovy side of the belt should go to the V-pulleys, and the flat side of the belt should go to the idle pulley. You should have a diagram somewhere on your Cub Cadet, so just refer to it for guidance.

Tighten the Blade Belt and Level the Deck Riding Mower Lawn Tractor Craftsman Murry

Put Everything Back Together

It’s very easy to get lost when putting the different parts of a machine like your Cub Cadet back again.

It’s important to keep track of the steps when replacing parts. You might find yourself confused about which parts go where, which is why it’s important to document the replacement process. This is a great way to be able to see if you did something wrong or not.

The video below should illustrate how the entire process is done:

Telltale Signs Of A Failing Drive Belt

A frayed Cub Cadet drive belt can make your mowing job much more difficult. A torn or frayed belt will be the cause of many problems that could cost you hundreds of dollars to repair. Here are the telltale signs to look out for of a failing Cub Cadet drive belt.

Losing Tension/Slippage

It’s important that the belt should be tight to avoid slipping. However, the belts can wear out ,and when they do, they lose some of their elasticity and become loose. As a result, the pulleys on the motor and the transmission become separated when the belt gets slack.

Engine Overheating

A worn lawnmower belt is a silent killer. Over time, an undetected worn belt may slip without warning. This means the belt may not be able to move the pulleys effectively and could cause your lawnmower to stutter and run intermittently while you’re mowing.

This will cause the engine to work harder than it should. It may even break down altogether, causing your lawnmower to grind to a halt. If you’re noticing excessive heat coming from the engine, this could indicate the belt is failing.

What Is The Purpose Of An Idler Pulley?

There’s an idler pulley in almost every machine. So what does an idler pulley exactly do, and why is it important?

An idler pulley is a part of the machinery where the belt passes through, providing a means of supporting the belt without slipping or getting damaged. It’s a crucial machine component that allows the motor to spin at a constant speed.

A pulley is a tool that allows one machine to work with another machine. In the case of an idler pulley, it’s a part of a belt system that allows a machine to move along with the rotation of the pulley.

In addition, it’s a device that is used to reduce friction and vibration between belts and pulleys. It is a mechanism that is used for providing tension and speed of the belt.

Should You Worry If The Idler Pulley Fails?

A common failure that occurs in a pulley mechanism is the idler pulley. These pulleys serve the purpose of taking the load of the machine and distributing it through various parts of the machine.

When the idler pulley fails, the load that it was meant to distribute will become concentrated on the remaining pulleys.

This can cause extensive damage to the drive belt and could lead to its destruction. As a result, you need to replace the idler pulley as soon as possible.

If your idler pulley fails, the drive belt may slip and no longer transmit the required power to the cutting blades. This can cause the blades to stop working, leaving you stuck in a very precarious situation.

In Closing

There are actually no settings that you can use to adjust the tension settings of your Cub Cadet drive belt. However, you must pay attention to the warning signs that your Cub Cadet needs a spring tensioner replacement. A loose drive belt is not something you should ignore.

How Tight Should A Mower Deck Belt Be For Top Performance?

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A mower deck belt is one of the most important parts of riding mowers. It is important to keep it tightened to ensure that it is performing at its best. The v belt helps to turn the cutting blades and is responsible for cutting the grass. If the belt is too tight, it can wear out too quickly, not transfer the grass cuttings to the bag, and also, the engine will have to work harder. This can lead to overheating.

If the belt is worn out, replace mower deck belt with a new drive belt.

How tight should a mower deck belt be on a riding lawn mower?

The deck belt on a mower should be tight enough to prevent slipping, but not so tight that the belt is being pulled too tightly. Your mower belt is responsible for transferring the power of the engine to the wheels of the mower. The belt is also responsible for propelling the blades of the mower to cut grass. It is important to keep the mower belt of your mower in good condition.

The mower belt usually breaks because of overheating. Overheating can be because of many things. In this article, we shall discuss the possible reasons and some tips on how to solve this problem. If the belt’s tension is not properly adjusted or if the belt is too tight or too loose, then the mower belt may break because of heat. This is because of two reasons.

One is that the loose belt will rub against pulleys and other components of the mower, and the heat from friction will cause it to break. The other reason is that the loose belt will vibrate too much and that will cause the belt to wear out faster or break. Super tight or too much tension on the belt is hard on the clutch pulley which could cause the bearings to wear out or overheat.

What can cause a lawn mower belt to slip?

A mower deck belt should be checked regularly to ensure it is operating properly. This can reduce the possibility of a broken belt which could lead to severe engine and transmission damage. Tensioning the mower deck belt to the correct level will improve its performance and longevity.

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Tensioning the belt yourself is a simple process that can be done in minutes.

Using the right tools

We recommend using a torque wrench and a belt tension gauge. You will need to know the measurement of the belt which can be found in the owner’s manual of your mower. If you can’t find it there, then you can determine it by measuring the distance from the center of the pulley to the tip of the blade.

What is the deck belt tension on my mower?

The deck belt tension on your riding lawnmower is a very important factor when it comes to the performance of your mower. When it comes to mowing, the deck belt tension on your mower is important. If it is too loose, the belt can slip. If it is too tight, the belt can break.

When it comes time to replace the old belt, I would recommend that you use a belt that is 1/8 inch smaller than the one you are replacing, instead of a larger belt. This is so that it will be a tight fit and not cause problems.

How to tighten a loose lawn mower belt on a riding lawn mower

The deck belt on my riding lawn mower was loose. It was flapping around and making a lot of noise. The belt was not just loose, it was about to fall off. I had to get it tightened.

One of the most common issues with riding lawn mowers is a loose belt. A loose belt can cause the mower to run slowly or not at all, and it can also damage the belt itself. The good news is that adjust belt tension is a relatively easy task that anyone can do.

First, locate the adjustment knob or lever. This is usually located near the pulleys. Next, turn the knob or lever to tighten the belt. Be careful not to over tighten the belt, as this can damage the belt or cause it to slip.

If the mower still won’t run after adjusting the belt, then the belt may need to be replaced. Replacing a lawn mower belt is a more involved task, but it is still relatively easy to do. Consult your owner’s manual for specific instructions on how to replace the belt.

  • Replacment deck belt for craftsman 42 144959 (a93) this belt is not oem belt. the oem number is jus
  • Blade drive belt 144959 (532144959) turns the pulley that spins the blades on the mower deck.
  • 1/2×95 odoutside dimension. you can find the inside circumference by subtracting 2 from the outsid
  • Note: there are many different belts for craftsman 42! please make sure this is the right one for y
  • This belt fits sears, poulan, Husqvarna, rally, ayp and many other brands of riders with 42 lift le
  • Replacement deck belt for craftsman oem 144959 Husqvarna 532144959. this belt is not oem belt. the o
  • 1/2 x 95 od (outside dimension.) 4l950-a93 you can find the inside circumference by subtracting 2
  • Note: there are many different belts for craftsman 42! please make sure this is the right one for yo
  • Drive belts fits models: ayp46 and 48 decks, 1998-2000 murray30 deck, 1992-1995; 38, 40, 42 an
  • Deck belts fits models: ayp24h4b3a with 46 deck craftsmanmost mowers with 38 and 42 deck husqvarn
  • Genuine oem deck belt for craftsman riding lawn mower / lawn tractor / lawn tractor
  • Oem fits newer model 917 style 42 craftsman rider. also fits many Husqvarna poulan 42 c
  • 1/2 x 101.4
  • Wrapped-molded / aramid cord construction / double cover / clutching
  • 1/2 x 101 outside dimension. you can find the inside circumference by subtracting 2 from the ou
  • Replacement mower deck belt for craftsman. 42 deck OEM part 42963, 197253
  • Replacement mower deck belt for john deere OEM part m84136, m87323
  • Note: there are many different belts for craftsman 42. please make sure this is the right one for you
  • This belt is not OEM belt. the OEM number is just for your help in looking for the belt you need
  • Replacement mower deck belt 405143 for craftsman, 532405143 Husqvarna Poulan. this belt is not an OEM belt
  • 1/2 x 106 outside dimension. you can find the inside circumference by subtracting 2 from the out
  • For craftsman (only 917. model # ) Poulan two (2) blade 46 decks
  • Note: there are many different belts for craftsman 46! please make sure this is the right one for y
  • Replacement numbers: the 144959 lawn mower drive belt can replace belt part number 144959, 532144959
  • Widely applied: this 144959 replacement deck belt is compatible with sears poulan ayp Husqvarna ct20
  • Product size: the 144959 drive deck belt is 1/2 inch/ 1.3 cm in width, 95.5 inch/ 242.6 cm in length
  • Easy to install: if the center distance between the two shafts is adjustable, first shorten the cent
  • Material structure: made of strong cushion rubber, strong tension and no elongation polyester rope,
  • Replace part number: mtd cub cadet 754-04060 954-04060 754-04060a 754-04060b 754-04060c 754-05056 95
  • Fits models: cub cadet lt1040 and lt1042, 42 decks; for 18 and 19 HP engines
  • Fits models: craftsman: most mowers with 42 decks
  • Fits models: j-d: stx38 ; sabre: 1438, 1538, 1542, 1642, 1646 and 1742
  • Fits models: mtd: deck assembly g with 42 deck, 2005
  • Deck belt is made of flexible rubber, and is used in conjunction with the pulley assemblies to trans
  • Compatible with 46 deck mowers including: Husqvarna: pb20h46lt, pb20h46yt, pb19546lt, yth21k46, yt
  • Also fit for: craftsman: 917287240, 917289240, 917288522, 917250830, 917253240, 917203830, 917203840
  • Easy to install. measures 1/2 x 105 3/4 to match 46 cut deck.
  • Replace oem part: ariens: 21546607 ayp: 405143, 584453101 craftsman: 7133156 Husqvarna: 53240514

As an affiliate, we earn from qualifying purchases. We get commissions for purchases made through links in this post.

Conclusion: Ensure the belt is tight enough

In conclusion, a mower’s deck belt can create problems if they do not work correctly or if they are too tight or it’s too loose. Replace the belt with a new one to avoid these issues and to make sure that your lawn mower may be at its peak performance.

To avoid these issues, it is best to replace your belt with a new one as needed.

I have been a DIYer for over thirty years and I love troubleshooting, building, fixing, and experimenting with new products. When not in the shop tinkering with some project or other, you can find me outside working on my yard.

You’ll often see me using power tools like pressure washers and lawnmowers to tinker around with different projects! Although I’ve been doing this for over 30 years, there are still plenty of ways that people can make things easier or more efficient- so stay tuned! report this ad

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How to Tighten a Belt on a Honda Lawn Mower

Self-propelled Honda lawn mowers use a belt and pulley to help drive the mower, making it easier to mow the lawn. Over time, the belt can stretch and start to slip. Fortunately there is a tension screw to put more tension on the belt and make it snug again, eliminating the need to replace the belt. Doing the job yourself saves you the time and money it would take to use a repair shop.

Step 1

Remove the grass clipping collector bag from the mower. Disconnect the spark plug wire from the spark plug and secure it away from the spark plug.

Step 2

Use the screwdriver to remove the belt housing on the mower deck. This housing is located near the rear wheels. Remove the screws and set the housing to the side.

  • Self-propelled Honda lawn mowers use a belt and pulley to help drive the mower, making it easier to mow the lawn.
  • Fortunately there is a tension screw to put more tension on the belt and make it snug again, eliminating the need to replace the belt.

Step 3

Locate the screw on the transmission pulley wheel. Insert the screwdriver into the screw and turn it clockwise to create more tension on the belt. The belt needs to be tight enough to stay on the pulley and not slip, while not so tight that the pulley no longer turns. Test the tension by carefully moving the belt through the pulley. Keep your fingers away from the pulley.

Step 4

Replace the housing onto the rear of the mower. Reattach the spark plug wire to the spark plug.

  • Locate the screw on the transmission pulley wheel.
  • Test the tension by carefully moving the belt through the pulley.

If the belt continues to slip and no more tension can be added, it may be time to replace the old belt, because it is probably too stretched.

Mower Deck Belt Replacement – Step by step

Replacing belts on your mower is like replacing tires on your car; there are only so many miles in them. Replacing a deck belt can be a challenge, especially if the mower throws the belt and you don’t know the routing, but we’ll get it figured out!

Getting the correct belt is the first important step. Some manufacturers place a label detailing the belt part number and belt routing. Try under the hood or under the footrest; if not, check out “Belt routing.”

Deck types vary. Some are easy to work on, some not so much. It’s important to check over the deck looking for any damaged or loose components, especially if your old belt was damaged and not just worn out. You don’t want to damage the new belt needlessly.

Most mowers won’t require deck removal to fit the belt; others will. So take some time and consider the routing, don’t put extra work on yourself. Take lots of photos; it saves time and head-scratching later.

What’s Involved?

Fitting the new belt means removing some plastic protective covers. And in most cases, it involves wrapping the belt around the pulleys and making sure the belt guide (guide not on all pulleys) is on the outside of the belt. The last pulley to fit is the crank pulley (engine pulley).

Tensioned or Not

A tension-ed belt is a deck drive belt that is always tight on the pulleys. Push-button blade engages type mowers usually run an always tension-ed belt. Replacing it will require manhandling the belt onto the side of the crank pulley, then turning the crank pulley clockwise by hand until the belt slips on.

If your mower has a lever, then you likely have a slack belt which is then tensioned by moving the blade to engage the lever. This type of belt is easier to replace and will take no time at all.

Tensioned – This type of belt is always tight on the pulleys.

Un-Tensioned – This type of belt setup is slack on the pulleys until you engage the blades.

What Deck Type?

Cutting deck setup types vary from side discharge; rear discharge; mulching decks; front decks; cutting, and sweeping.

They may have features such as single-blade; twin-blade; tri-blade; tensioned belt; manual tensioned belt; electromagnetic blade engagement; fan assisted deck; timed overlapping blades, and so on.

The one thing they all have in common – is the deck drive belt. It’s how engine power is transferred into cutting power.

Timed Deck

A timed deck means both your mower blades are set at a fixed angle in relation to each other. The toothed belt maintains the blade position; this allows the blades to overlap.

Some say the overlapping blades give a superior cut; I like the lawn finished with the overlapping twin cut, especially the smaller decks.

This deck type is also referred to as an interference deck. They call it Interference because if the blades go out of time, they’ll smack each other.

Resetting the timing of the blades or replacing the belt is a job that can be done without much difficulty, but it does require removing the deck, tension assembly, and various plastic guards. No special tools are needed.

Rear – Rear discharge is great at collecting grass but doesn’t like long grass so much.

Timed – Timed deck has a toothed belt that can break or slip out of time. Timing the blades allows them to overlap.

Mulching – Some decks will have a flap that closes off the chute when the operator wants to mulch.

Side Discharge – Side discharge is great for tall grass and rough terrain.

Measuring The Belt

A belt will be marked with a type code, length, and part number. Belts are usually measured by their inside length (Li) or outside length (La); if you can find this info on the side of your old belt, great! But usually, it’s worn away.

Some mowers like Husqvarna place a sticker inside the hood with a list of helpful part numbers like belts, filters, plugs, etc.

What Belt Width? – The width and depth of a belt are also very important. A new V belt should fit snugly into a v pulley; the belt should sit just proud of the pulley’s shoulder. A belt that sits further down into the pulley is worn out.

What Belt Length? – If your belt was shredded, then you’ll need your make and model number to order the correct belt. An easy way to measure an old belt – use a string to follow the outside of the belt; now measure the string.

This measurement will be marked on belts by the letters La (outside measurement); alternatively, run the string around the inside of the belt; this measurement is the Li measurement.

A faster way to measure an intact belt is to make a circle of the belt and measure inside to inside, then multiply by 3.14. The result is the Li belt size.

Sizing – Sometimes easier said than done!

Markings – Check under the hood of your mower; you may get lucky with a part number sticker, but be cautious with the Husqvarna labeling; they are often wrong belt part numbers.

Check your old belt for markings; if none, get the tape and some string. These belts are measured in mm.

Pulley – The new belt will be the full width of the pulley. Worn belts usually stretch in length and become narrow in width.

Check Belt Routing

Belt routing, needless to say, is important. On some mowers, it’s possible to put a belt on the backways, which makes the blades turn backward. Not much use for yard work.

If you can, make a diagram or take some pictures of the old belt in place. First, you’ll need to remove both plastic protection pulley covers, one on each side. Some mowers have a handy sticker showing the deck belt routing under the footrest.

That’s great advice, but what if your belt has snapped or derailed? Then you’ll need to check out the links below. Bear in mind, even if you don’t see your maker in the list, check the link out anyway because lots of make share the same decks.

Look at the pulley configuration to see if yours looks similar.

Belt Routing Links

The following link to Google belt routing pictures:

Sticker – Check under the footrest of your mower; some models have a belt routing sticker. This sticker is on a Husqvarna tractor.

Check out the Amazon link below for deck belts.

What Belt Type?

Belts are belts, right? Well, No. The correct belt is crucial. An ill-fitting or wrong-type belt will cause endless trouble. Throwing the belt, vibration, poor cutting, and collecting, and because the belt doesn’t fit correctly, it won’t last very long. I had one customer who fitted a belt that was so tight it broke the end of the crankshaft. Ouch!!

There are many different types of belts; however, when it comes to lawnmowers, they are usually fitted with a standard V-type belt. Other belts used are AA belts, timed belts, and poly V belts.

Sure, you can fit a basic quality belt with a polyester cord, but it’s going to wear out quickly; for durability, you’ll want Kevlar; they cost more but last a lot longer. Some models will only work well with OEM belts, like John Deere and MTD.

I recommend fitting only OEM (Original Equipment Manufacturer). Fitting a belt can be a challenge. Reassembling and discovering what doesn’t work right can be demoralizing.

V Belts

V belts are so-called because of their cross-section shape (wider at the top than the bottom). They are used almost exclusively to drive power from lawn tractor engines to their transmissions. They are also used to drive deck blades. The V belt drives power from one side of the belt only.

They come in different heights/widths and are marked type A, B, C, D. The most common V belts used on mowers are the A and B types, and obviously, they come in a long list of lengths.

Each belt is marked by type and belt length; it may also have a part number. Unfortunately, the markings usually wear off, making the ID process difficult.

AA Hex Belts

The AA belt is a double-sided hexagonal belt; it is mostly used on tractor mower decks to drive the blades. The belts are unique as they have the ability to drive from either side of the belt.

AA Hex Type – This is a double-faced belt; it gives greater flexibility to deck design, as it allows both sides of the belt to drive. It’s used on higher-end tractor decks.

Toothed (Timed) Belts

A mower-toothed or timed belt does two jobs, it transfers power and, at the same time, keeps the mower blades from hitting each other. The toothed belt is a very exact belt in that the teeth of the belt must match that of the mower cogs.

Timed Belt – This type of belt has become more popular in recent years. It’s fitted to mower decks with overlapping blades.

A Type

A Type.This is the most common type of lawn tractor belt; it’s used by many lawn tractor drive systems and most decks too.

B Type

The B-type belt is a heavy-duty A belt; it’s an older well-fed brother.

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Check Belt Wear

Belts have a difficult job and can be the cause of various issues. Regular inspection will tell you if your belt is at the end of its life. Things to look for are flat-spotting, glazing, cracking, fraying, and contamination.

As you know, a V belt should sit just proud of the pulley shoulder; if it’s a lot lower than the shoulder of the pulley, it’s worn out.

How Long Do They Last?

The life of a belt is hard to gauge, it really depends on how much grass you’re cutting and how heavy the workload is, but usually, we’re talking years. Typically a belt should be changed after 3-4 years, but we know this doesn’t happen.

lawn, mower, belt, slipping, tight

A worn or damaged pulley can shorten the life of your belt. An engine or transmission oil leak can destroy the belt, you can try cleaning it, but it causes slip. A derailing belt can get twisted and damaged, and a mower that throws belts regularly probably has a worn or damaged pulley.

But the real killer of belts – tall, heavy grass jams the blades, which causes flat spots on the belt. The flat spot will then cause a lot of vibration, which in turn can throw the belt.

Belt damage is usually caused on the first cut of the season when the grass is heavy. So if your grass is tall and heavy, just take a little off on the first pass and make a second pass with the deck a notch lower. Yes, it’s twice the mowing, but it’s better for your mower and your lawn.

Flat Spot – Flat spotting is usually caused when the blade jams, but the engine pulley keeps running. This has a grinding effect on the belt.

The flat spot will cause excessive vibration in the mowing deck. The fix is – Replace the belt.

Blistering – This can happen when a belt gets old, and the material starts to break down. Your mower won’t cut or collect very well. Better to take care of it now, before it breaks.

Glazing – This belt has a shiny hard surface that is not much good for traction. A belt like this will cause horrible vibration in the mowing deck.

Frayed – Wear and tear, this belt is at the end of its useful life.

Cracked – Natural wear and tear

Check Pulley Wear

A pulley’s job is to route the belt around the chassis of the mower or mowing deck and transfer power from the engine pulley to the driven pulleys. As a rough guide, pulleys usually wear out at the same time as a belt, so best to check them while you have the belt removed.

Tension and idler pulleys should move freely, be quiet when spun, and should feel smooth when turned. If they’re worn, now’s the time to take care of it; when a pulley bearing breaks, it will likely damage the belt.

Spin To Test

You don’t need to remove them to check. Spin them while the belt is off; they should be smooth and quiet. Changing them now is easy.


Most pulleys come with the new bearings pressed in place; the exceptions are driven pulleys (Mandrel, engine, or transmission pulleys).

Pulley Types

Pulleys come in all sizes, some metal and some plastic. Tensioners and idlers will have a bearing fitted, and when it wears out, the whole pulley is replaced. Pulleys are usually broken into two main types, flat or V.

A flat pulley is not a driven pulley; it runs on the back of the belt, which isn’t powered (unless it’s on a AA belt).

A V pulley can be driving, driven, tensioner, or idler. A V pulley is described as a driven pulley if it’s connected directly to the output, such as a transmission or a blade Mandrel.

The driving pulley is the engine pulley; it’s the pulley supplying the power. Both the driven and driving pulleys are fixed to shafts using a key and key-way.

A tensioner pulley is part of a moving arm, which, when operated, applies tension to a belt. A tensioner pulley can be a flat or V pulley.

A stationary pulley is usually known as an idler, and its job is to route the belt around the chassis of the mower or mower deck; they can be flat or V-type.

Pulleys – Metal or plastic, V type or flat, driven or idle. So many choices.

V Pulley – This is a V pulley; the driving side of the belt is making contact with the pulley.

Flat Pulley – A flat pulley on a V belt setup is never a driven pulley. Its job is to change the direction of the belt and guide it to the next pulley.

Fitting A Belt

Fitting a cutting blade deck belt that is just worn is the easiest, as you can see the routing of the old belt, and make a diagram or take pictures. Removing the old one also gives you an idea of how challenging fitting the new one will be.

As you know, there are a few variations of deck belt setups; most mowers will have one belt to drive the blades that are either a tension-ed or a un tension-ed belt. The belt can be fitted to both of these types of setups without removing the deck from the mower.

The timed belt setup is a little more involved but not complicated. It has two belts as do so some of the larger John Deere mowers. They can be a challenge as they have many pulleys, and you’ll need to remove the deck.

Pulley Covers

Likely you’ll have already removed the two plastic pulley protection covers, one on each side of the deck. Usually, 2 or 3 screws on each side. They’re not there to protect the pulley. They’re there to protect us from catching body parts in the pulleys.

The latest generation mowers are far more challenging to access as the nice people in the health and safety dept. have been working nights and weekends to find new ways to challenge us.

Removing Belt

Here’s a quick run-through of what we’ll be doing, but it’s all covered in the steps below with pictures. With the covers removed, start by removing the belt from the engine pulley. Often the engine pulley will have a belt guide; its job is to prevent the belt from derailing. Depending on the type of belt guide (if fitted), you may need to remove them first.

As you know, some belts will be tensioned all the time. By tension-ed, I mean the belt is tight around the engine pulley all the time.

The belt tensioner will allow for movement (it’s spring-loaded) so the easiest way to do this is by pulling the belt over the side of the engine pulley and then, with both hands, turning the engine pulley until the belt falls off (Removing the spark plug makes turning the pulley easy).

With the belt off the engine pulley, it’s easy to guide it off the other pulleys. Check your old belt against your new belt, just to be sure.

The un-tensioned belt is simple to fit, and by un-tensioned, I mean the belt is loose around the engine pulley until you engage the blades. The belt can usually be maneuvered around the guides without much trouble.

As with the tension-ed belt, remove the belt from the engine pulley first.

Fitting Belt

Reference your diagram or pictures of routing. Refitting the belt is identical except in reverse order, fitting the engine pulley last by pulling the belt onto the side of the pulley and turning the engine over.

Timed Belt

Most mowers have a simple deck belt setup, like the one covered in this guide is more complex. The demo mower used here has two deck belts driving the mowing deck.

The first one is the main input belt which is powered directly by the engine. This belt is easy to replace, and you don’t need to remove the deck, just some plastic covers.

The second belt is the output belt, and it turns both blades in time. This allows the cutting blades to overlap and catch that annoying tuft of grass you sometimes see in the middle of your cutting strip.

To replace the output belt also known as a toothed belt or timed belt, we need to remove the deck from the mower. It’s not difficult to do, and the whole job shouldn’t take more than an hour.

This guide covers a timed deck belt replacement procedure. Most timed decks will look something similar. It’s more complex than other deck belt setups but not difficult to work on. In this guide, I will: remove the deck; inspect belts; replace the belt; tension the belt; set the timing of the blades.


No special tools are needed on this mission, but an impact gun would make life a lot easier. When you try to open bolts attached to pulleys, they tend to spin, which is a real pain. Sure, you can wedge it or grab it with grips, but you risk damaging the face of the pulley, and that in turn can damage your new belt. Nooo!

The impact makes small work of pulley bolts, and the better brands have a torque setting built-in which makes reassembly a gift. It’s a super tool to have in the trunk of your car; it makes changing a wheel look NASCAR slick. So treat yourself or drop a few hints before fathers day.

Chute – On this model mower, the chute is fitted through the center of the mower. Not all mowers will have a chute like this. If your mower is side discharge, then you don’t have one.

Remove – As said earlier, you may not need to remove your deck to fit a belt. On this model mower, removing to fit the belt just makes life a little easier.

Pins – Locate the deck arms. Most mowers will have one at each of the four corners. The deck will be fixed to the deck arms with Cotter pins. (Some may have nuts and bolts) Remove the two front pins and the two rear pins.

Slide – The deck will be free to move forward, which allows you to remove the deck drive belt from the engine drive pulley. In some cases, you may have a cable to remove; this depends on the blade engage type.

Push – With all pins removed and belt off, just push the deck sideways and it will pop off the arm bushing mounts. Apply some grease when refitting. Hey, I make that sound easy!

Inspect – Go ahead and turn the deck over to inspect the blades and blade boss (blade attachment). It’s likely that the blades are damaged; if they are, replace them.

Bent – If your blades are bent or worn, now is the time to take care of them. Replacement blades are easy to fit when the deck is off.

Boss – When your blade hits something hard, the blade boss pins are designed to break; this saves damaging more expensive components.

Replace – Check washers and bolts for damage. Blade bolts and washers are specially designed, so only use the original kit.

Remove – Remove plastic protection covers.

lawn, mower, belt, slipping, tight

Pulley – Remove the drive belt tension assembly.

Key – Remove and store the key and the spacer ring safely.

Remove – Remove the timed belt protective cover.

Belt – Remove the broken belt, and check for damage.

Loosen – Loosen both pulley bolts; the bolts are positioned on the underside of the pulley.

Remove – Remove the two guide bolts. Remember to fit these after fitting the belt, but tighten them last.

Loosen – Loosen the two guide bolts.

Loosen – Loosen the lock-nut on the adjusting bolt, and thread it all the way out.

How to add tension to a mower deck belt

Push – Now push the tensioning assembly in all the way so it hits the adjusting bolt.

Set to 90° – Set the deck blades at 90° to each other.

Mark – Now mark the two main blade pulleys and the deck body as per the picture. Marking them with paint gives us a clear reference point when fitting the new belt.

Align – Keep your paint marks aligned and fit the belt to the tension assembly last.

Check – Check your paint marks again; it’s OK if you’re out by one or two teeth.

Routing – This is a typical timed belt routing.

Adjust – Adjust belt tension first, and tighten down the lock-nut. Do not tighten pulley bolts or guide bolts at this stage.

Check – Check belt tension as you adjust. Leave some play in the belt; it should deflect by about 1/2″ at its longest run.

Check 90° – Check that the blades are at 90 degrees. If all is OK, go ahead and fit the guide bolts, but don’t tighten them yet. Tighten the two pulley bolts, and now tighten the four guides.

Rebuild covers and fit the deck in reverse order; that wasn’t so bad!

Related Questions

Why does my deck belt keep breaking? Common reasons new belts keep breaking:

Why does my mower deck shake? Mower decks commonly shake because:

  • Engine not at the correct rpm
  • Engine not running correctly
  • Blades damaged
  • Deck belt damaged or worn
  • Spindle bearing damaged or broken

As you’re a MacGyver type, you’ll likely find the Riding mower troubleshooting and the Video repair library useful.

Hey, I’m John, and I’m a Red Seal Qualified Service Technician with over twenty-five years experience.

I’ve worked on all types of mechanical equipment, from cars to grass machinery, and this site is where I share fluff-free hacks, tips, and insider know-how.

And the best part. it’s free!

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