Husqvarna mower belt loose. 9 Fixes For When Your Lawn Mower Won’t Start

And how to replace ​lawn mower belts​

Lawn mower blades on a zero turn lawn mower aren’t driven directly by a PTO (power take off) shaft or by an engine crankshaft. Instead, they’re turned by a system of pul​leys which are driven by a belt that’s powered by the electric clutch and the engine. Too m​uch technical information? That’s ok, you don’t necessarily need to know all of that, but what you do need to know is that lawn mower belts wear, and if neglected, eventually break.

When to replace lawn mow​​​er belt?

Obviously, a broken zero turn lawn mower belt or broken lawn tractor belt results in the automatic need for a belt replacement, but how can you catch it before it fails while mowing and inconveniencing your weekend schedule? There’s no definite amount of time that a mower belt is supposed to last, but increased mower use shortens the interval in which a belt needs replacement. Simply put, more use equals more wear.

Additionally, faulty belts or mechanical failures like a seized pulley can make lawn mower belts break prematurely. If you’re wearing through belts more frequently than what seems normal, you may be sourcing inferior belts, or are experiencing a mechanical failure in the form of a seized pulley, a burr (sharp metallic rough spot) on the pulley, or some other interference along the path of the belt routing.

How to tell if a mower belt ne​​eds replacement

Visual inspection is all it takes to know if a mower belt is beyond its life, and it doesn’t take a rocket scientist or experienced mechanic to see the signs of wear that appear before an impending break. The average homeowner will be able to spot a wearing belt as long as they know what to look for.

These signs show when a mower belt could experience failure and needs replacement as soon as possible:

The belt has s​​​ide wall damage.

Mower belt edges should be smooth and even throughout the entire length of the belt. If even a small portion of the belt is worn, it’s at risk of breaking and should be replaced.

The belt has a glazed or bu​rned sidewall.

Look at the belt edge that contacts the pulleys. If it appears shiny, glazed or burned, it will need to be replaced.

The belt is​​ cracked.

If the belt appears brittle and is deteriorating to the point that it has cracks, even shallow cracks, it is at high risk of breaking and needs to be replaced.

How to replace a lawn mowe​​r belt

Replacing a mower belt is easy and doesn’t take too much time, even for those who don’t have much, if any, mechanical experience. All it takes are a few wrenches, and about 1.5 hours on a Saturday morning. Alternatively, if it’s a process you’re uncomfortable doing yourself, your local Ariens dealer will be glad to complete the service work for you.

Watch the step-by-step process on how to change a lawn mower belt on an Ariens IKON X or IKON XL of any deck size. As always, before you start service, park the unit on a flat, level surface, stop the engine, remove the key and wait for all moving parts to stop and for hot parts to cool. Additionally, reread all the safety information in the operator’s manual for your unit.

Set the cutti​​​ng height of the mower to its lowest position.​​

Remove the belt covers from the left and right sides of the mower deck.

Pull belt out of the left spindle pulley to release belt tension on the mower belt idler spring.

Identify the mower belt idler arm and remove the hardware above the belt finger / guide the so the idler spring hook can be accessed.

With safety goggles and an adequate spring pulling tool, remove the spring from the idler arm assembly.​

Raise the mower deck to it’s highest cutting position.​

Loosen the hardware retaining the idler assembly to the mower deck and remove the idler assembly. To remove the nut from the bolt, the bolt head under the deck will need to be held in place with another tool. Use caution when reaching under the mower deck.

Return the mower deck to its lowest cutting position.

Remove hardware retaining the belt finger from rearmost idler pulley and remove the belt finger.

Remove the​​ belt from the clu​tch pulley located under the engine.

Remove​​ the​​ be​​lt.​​

Install the new mower belt around the spindle pulleys and the idlers on the mower deck. It’s difficult to tell how the mower belt is routed in the picture below​, so reference the diagram in the operator’s manual for your unit to see exactly how the belt should be routed.​

​Additionally, it’s crucial the belt is installed in the correct orientation. Looking closely at the belt, you can see that the belt has a V shape, which gives one side of the belt less surface area than the other side of the belt. It’s very important to install the belt so the side with less surface area is positioned against the spindle p​​ulleys.​

Ensure the belt is against the rearmost idler pulley and reinstall the belt finger for that pulley with its original flange nut.​

Install the mower belt around the clutch pulley at the rear of the unit.

Return the idler assembly to its original position. Ensure the large flat steel washer is positioned between the idler and the deck, and ensure the small flat steel washer is positioned on top of the idler.​

Raise the mower deck to it’s higest position and reinstall the idler assembly hardware, but finger tighten only. DO NOT completely tighten the hardware. Then, move the belt under the idler pulley so it’s in the orientation shown in the image below.

Safely reach under the deck to access the idler arm assembly bolt head. Hold the bolt head in place and tighten the nut to secure the idler arm assembly.

Adjust Mower Deck Belt

Lower the mower deck to its lowest cutting height.

Reinstall the belt finger into the idler arm. Then, while wearing safety goggles, reinstall the idler spring hook around the idler assembly.

Ensure the belt has tension and is correctly aligned in all pulleys.

Reinstall the spacer onto the idler assembly and secure with the original flange nut.

husqvarna, mower, belt, loose

​22. Reinstall the left and right belt covers with the original hardware.​

Where to order lawn ​​mower belts

If your belts are worn and want to try this procedure on your own, visit your nearest Ariens dealer for replacement parts, or source belts from the Ariens online parts store at But again, if you aren’t comfortable completing this procedure on your own, visit your Ariens servicing dealer for help.

To learn which belts you need for your mower, click here to watch our 47-second video that shows how to identify replacement part numbers on your unit and how to find them online.​

There are a number of reasons, mechanical and otherwise, why a mower won’t run. The good news is that fixing most all of the issues is easy enough for a DIYer to handle.

By Tony Carrick and Manasa Reddigari | Updated Aug 8, 2022 4:03 PM

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Lawn care can be tedious, but once the grass starts growing in the spring, mowing becomes a fact of life in most neighborhoods. When you finally muster the strength to tackle that first cut of the season, there are few sounds as disheartening as that of a lawn mower engine that turns over but doesn’t start.

Before you drag the mower in for repairs or invest in costly replacement parts, first make sure that a clogged air filter, soiled spark plug, damaged safety cable, clogged mowing deck, or contaminated gas isn’t to blame. Work through the following steps, and you may be able to get your puttering grass guzzler up and running again in no time.

A lawn mower repair professional can help. Get free, no-commitment repair estimates from pros near you.

Change the lawn mower carburetor filter.

Your lawn mower’s air filter guards the carburetor and engine from debris like grass clippings and dirt. When the air filter becomes clogged or too dirty, it can prevent the engine from starting. To keep this from happening, replace paper filters—or clean or replace foam filters—after every 25 hours of engine use.

The process for removing the filter depends on whether you are operating a riding or walk-behind lawn mower. For a riding mower, turn off the engine and engage the parking brake; for a walk-behind mower, pull the spark plug wire from the plug. Then, lift the filter from its housing.

The only choice for paper filters is replacement. If you’re cleaning a foam filter, wash it in a solution of hot water and detergent to loosen grime. Allow it to dry completely, and then wipe fresh motor oil over the filter, replace it in its housing, and power up the mower—this time to the pleasant whirring of an engine in tip-top condition.

Check the spark plug.

Is your lawn mower still being stubborn? The culprit may be the spark plug, which is responsible for creating the spark that ignites the fuel in the engine. If it’s loosened, disconnected, or coated in water or carbon residue, the spark plug may be the cause of your machine’s malfunction.

Locate the spark plug, often found on the front of the mower, and disconnect the spark plug wire, revealing the plug beneath. Use a socket wrench to unscrew the spark plug and remove it.

Check the electrode and insulator. If you see buildup, spray brake cleaner onto the plug, and let it soak for several minutes before wiping it with a clean cloth. Reinstall the spark plug, first by hand, and then with a socket wrench for a final tightening. If the problem persists, consider changing the spark plug.

Clear the mower deck of debris.

The mower’s deck prevents grass clippings from showering into the air like confetti, but it also creates a place for them to collect. Grass clippings can clog the mower deck, especially while mowing a wet lawn, preventing the blade from turning.

If the starter rope seems stuck or is difficult to pull, then it’s probably due to a clogged deck. With the mower safely turned off, tip it over onto its side and examine the underbelly. If there are large clumps of cut grass caught between the blade and deck, use a trowel to scrape these clippings free. When the deck is clean again, set the mower back on its feet and start it up.

Clear the vent in the lawn mower fuel cap.

The mower started just fine, you’ve made the first few passes, then all of a sudden the mower quits. You pull the cord a few times, but the engine just sputters and dies. What’s happening? It could have something to do with the fuel cap. Most mowers have a vented fuel cap. This vent is intended to release pressure, allowing fuel to flow from the tank to the carburetor. Without the vent, the gas fumes inside the tank begin to build up, creating a vacuum that eventually becomes so strong that it stops the flow of fuel.

To find out if this is the problem, remove the gas cap to break the vacuum, then reattach it. The mower should start right up. But if the lawn mower won’t stay running and cuts off again after 10 minutes or so, you’ll need to get a new gas cap.

Clean and refill the lawn mower fuel tank.

An obvious—and often overlooked—reason your mower may not be starting is that the tank is empty or contains gas that is either old or contaminated with excess moisture and dirt. If your gas is more than a month old, use an oil siphon pump to drain it from the tank.

(It’s important to be careful as spilled oil can cause smoking, but there are other reasons this might happen. Read more about what to do when your lawn mower is smoking.)

Add fuel stabilizer to the tank.

Fill the tank with fresh fuel and a fuel stabilizer to extend the life of the gas and prevent future buildup. A clogged fuel filter is another possible reason for a lawn mower not to start. When the filter is clogged, the engine can’t access the gas that makes the system go. If your mower has a fuel filter (not all do), check to make sure it’s functioning properly.

First, remove the fuel line at the carburetor. Gas should flow out. If it doesn’t, confirm that the fuel shutoff valve isn’t accidentally closed. Then remove the fuel line that’s ahead of the fuel filter inlet. If gas runs out freely, there’s a problem with the fuel filter. Consult your owner’s manual for instructions on replacing the filter and reassembling the mower.

Inspect the safety release mechanism cable.

Your lawn mower’s reluctance to start may have nothing to do with the engine at all but rather with one of the mower’s safety features: the dead man’s control. This colorfully named safety bar must be held in place by the operator for the engine to start or run. When the bar is released, the engine stops. While this mechanism cuts down on the likelihood of horrific lawn mower accidents, it also can be the reason the mower won’t start.

The safety bar of a dead man’s control is attached to a metal cable that connects to the engine’s ignition coil, which is responsible for sending current to the spark plug. If your lawn mower’s engine won’t start, check to see if that cable is damaged or broken. If it is, you’ll need to replace it before the mower will start.

Fortunately, replacing a broken control cable is an easy job. You may, however, have to wait a few days to get the part. Jot down the serial number of your lawn mower, then head to the manufacturer’s website to order a new cable.

Check to see if the flywheel brake is fully engaged.

The flywheel helps to make the engine work smoothly through inertia. When it isn’t working properly, it will prevent the mower’s engine from working.

If it is fully engaged, it can make a mower’s pull cord hard to pull. Check the brake pad to see if it makes full contact with the flywheel and that there isn’t anything jamming the blade so the control lever can move freely.

If the flywheel brake’s key sheared, the mower may have run over something that got tangled in the blade. It is possible to replace a flywheel key, but it does require taking apart the mower.

Look out for signs that the mower needs professional repairs.

While repairing lawn mowers can be a DIY job, there are times when it can be best to ask a professional to help repair a lawn mower. If you’ve done all of the proper mower maintenance that is recommended by the manufacturer, and gone through all of the possible ways to fix the mower from the steps above, then it may be best to call a pro. Here are a few signs that indicate when a pro’s help is a good idea.

  • You see black smoke. The engine will benefit from a technician’s evaluation, as it could be cracked or something else might be worn out.
  • Excessive oil or gas usage. If you’ve changed the spark plugs, and done all of the other maintenance tasks, and the mower is consuming more than its usual amount of oil or gas, consult a professional for an evaluation.
  • The lawn mower is making a knocking sound. When a lawn mower starts making a knocking sound, something could be bent or out of alignment. It may be tough to figure this out on your own, so a pro could help.
  • A vibrating or shaking lawn mower can be a sign of a problem beyond a DIY fix. Usually something is loose or not aligning properly.

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.

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

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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!

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Husqvarna Mower Drive Belt Problems | Get the Easy Solution in 10 min

If you have a big lawn then you should buy a Husqvarna mower to mow the lawn smoothly. It is a fabulous invention to cut the grass on a large area. Cutting the grass on your lawn is an easy task when you know the proper use of the lawnmower. You must know the function of every part of the Husqvarna mower if you want a perfect execution.

One of the common problems is the Husqvarna Mower Drive Belt Problem that you have to know how to fix. What do you know about the drive belt? The drive belt is a very crucial part of the mower. The drive belt has an important role in mowing. It determines whether the wheel will move or not.

The drive belt is also known as the blade belt. If something goes wrong with this then your mower will not run. If the belt is damaged your mower will move slowly because the belt slides on the pulley. Sometimes the belt can be loose. Here I will discuss how to adjust the belt tension.

If you understand the Husqvarna drive belt diagram then Husqvarna mower drive belt adjustment will be easy for you. Don’t panic about it. This blog will help you a lot.

Step 1: Park your mower on a plane surface

As always you must put the mower on a smooth, even, and level surface. Make sure the easy access to the underneath of the mower. Stop the mower properly. Use a parking brake to prevent moving. Carefully tilt the side of the mower otherwise the oil can run out from the reservoir. It would be best if you use the lift to raise the mower.

Before starting this process you should run the mower in a well-ventilated zone for a few minutes. If the belt and pulley work for a while then you will be able to move the pulley easily. This easy step will make the Husqvarna drive belt installation easier.

Step 2: Detach the Spark Plug

You may think why should I disconnect the plug? Right? You should disconnect the safety plug for your safety. While working with the belt the engine can start unintentionally. If you remove the spark plug then the engine can not start automatically. On one side of the combustion chamber, the spark plug is found. You must unplug it.

Some people remove the cutting deck while repairing the drive belt. But it has both advantages and disadvantages of removing the cutting deck. But I think lowering the deck will provide you enough scope.

Step 3: Turn the Log Lever.

Log lever is important for engaging and disengaging the Husqvarna mower blades. It can be seen nearby the steering wheel and from the top of the control panel. It arises out of the control panel and continues to the right and so it turns at a 90-degree angle. Grasping the paddle handle twists the log lever.

Step 4: Investigation of Blade Belt.

Then find out the Husqvarna blade belt. I hope you know about the belt and pulley system. You can find it underneath the seat. To investigate this part you must put the mower on a raised floor.

Look at the belt and try to find any crack on it. If there is any crack or chunks you should repair it as soon as possible.

You must inspect the spring arm whether it works properly or not. Does your spring arm go back and forward smoothly? Inspect this thing.

There is a spring in the spring arm. Make sure that the spring is easily expanded by hand. That means the spring should be loose. Also, you need to check the distortion of the belt. Distortion must be adjusted so that the belt can pass over the pulley perfectly. You can loosen the belt whenever you feel that the belt is too tight.

over, you will find a wire that arises from the blade engagement level. It can be enlarged over time, so the belt gets obscure. You should fix this issue as well.

Step 5: Adjustment of Mower or Blade Belt.

All done. Now you may go for the adjustment process. You can find a small bracket. It helps to adjust the cable. You know the blades and deck are disentangled so everything under the deck is in a loose position. You need to tighten the screw over the spring arm.

Now unbolt the washer and screw with the help of an adjustable wrench. Then shift the bracket away. Tighten the bolts and put them in their position back. Make sure there is a proper interval between the bracket and spring. Use a 10 mm wrench for the bracket bolting and unbolting in case of Husqvarna.

When all these things are done put the log lever away and try to engage the blades and mower deck. It would be better if you use grease in the belt before running the mower. over, you should lubricate the pulley also.

Step 6: Double-check the Blades.

Check whether the belt and pulley system is operating well or not. Wearing safety gloves wrap the blades. Make sure that the belt runs over the pulley without slackening or drooping. So easy. All done! Now attach the spark plug and try to begin the Husqvarna engine.

Frequently Asked Question:

1.When should I repair my mower belt?

If Your Push Mower Won’t Start, Do This! A step by step guide to getting your push mower running.

Nobody can ensure the exact lifetime of your mower belt. There is no fixed amount of time. When the belt needs adjustment you can fix it any time. But it is the best decision to replace the belt every two seasons. After a heavy mowing season, you need to replace the belts to protect the mower from any other serious issue.

2.Does a lawn mower drive belt extent?

Yes, a drive belt can extend. You may hear about the wear and tear effect. Due to this effect, the mower belt will stretch. Unlike the car’s belt, the mower belt is less strong. The belt and blades revolve very fast. Repeated heating and cooling is the main cause of the stretch of the mower belt.

3.Why does my drive belt keep coming off?

When a drive belt becomes loose or damaged the melt may get out. A worn belt can cut while you run the engine. It can be very risky for you. So replace the belt when you notice any crack or damage on the belt.

Bottom Lines

A bad drive belt is a potential cause for your Husqvarna mower to run slow suddenly. You must know the belt adjustment process. I think this article is enough to teach you this process. Follow our guidelines and try this at your home. You don’t need any expert to do this.

Read Our Latest Article:

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.

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.

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.

husqvarna, mower, belt, loose

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.

husqvarna, mower, belt, loose

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.

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.

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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