Belt Keeps Coming Off Your Kubota Lawn Mower (Solved!)

It’s frustrating to have to stop mowing and reinstall your deck belt. It’s increasingly frustrating when it happens multiple times. Some Kubota model mowers require you to remove the mower deck each time which can make installing the belt more of a pain.

Finding the cause of your Kubota mower belt problem is necessary to stop this endless cycle of reinstalling your belt.

A Kubota mower belt may come off your mower when it becomes loose or worn; a bracket is worn or damaged; a bearing failed in a pulley or spindle, or debris is collecting on your mower deck preventing the components from functioning correctly.

I am sharing the items that can cause your belt to keep coming off your mower along with how to troubleshoot and resolve the problem. Take safety precautions to prevent your mower from starting or rolling. This can be done by removing the ignition key and spark plug wires.

Set your parking brake and use wheel chocks. Take extra safety precautions while working under your mower deck. Refer to your Kubota operator’s manual for additional safety tips.

9 Reasons Your Kubota Belt Keeps Coming Off Your Lawn Mower

Loose or Worn Kubota Belt

A Kubota belt doesn’t last forever. It eventually wears from normal use and must be replaced. Look for signs of a stretched or worn belt.

A belt that is installed correctly that doesn’t sit securely against your pulleys may be stretched. A worn belt is one where it is showing signs of cracking, or fraying or has a shiny glazed appearance.

A belt that is sitting deep in the grooves of your pulleys is another sign your Kubota belt is worn. When you find any of these conditions, replace your Kubota belt. I like using OEM (Original Equipment Manufacturer) belts purchased from my local Kubota dealership.

You can bring your belt to a local automotive dealership and have them try to match it up, but chances are you will not get an exact match.

From years in the industry repairing Kubota mowers, I have found these belts do not perform as well or last as long as OEM belts. Running an incompatible belt can pose safety risks.

Shredded Kubota Belt

When your mower belt is shredded along the edges, you must identify the cause of the shredding and fix it. Not doing so will be costly as you keep going through Kubota mower deck belts.

It’s not unusual to see a mower deck belt cost up to $200. A shredded belt is weakened and susceptible to breaking.

There are a couple of reasons your mower deck is shredded. One reason is the belt has been installed incorrectly. Make sure your belt is routed correctly by referring to your owner’s manual.

You can try looking at a parts diagram. Most of the time, a Kubota parts diagram is not helpful as it doesn’t show images of how your belt is to be installed. No worries if you can’t find your owner’s manual. Your local Kubota dealer should be willing to help.

Another reason for a belt shredding is when a belt is rubbed against a metal bracket. Locate the bracket causing the issue and attempt to bend it back into place. Replace the bracket if you are unable to bend it back into place.

If it happens to be a bracket with a bushing, you may have to replace the bushing or bracket assembly. Still unsure which piece your belt is rubbing against? Look for a shiny smooth spot that is created from the rubbing.

Kubota Idler Tensioner Bracket or Spring is Worn

Take a look at the idler tensioner bracket and spring. You will typically find a pulley mounted to one side of the bracket and a spring attached to the other side.

The spring can become weak or fall off causing your belt to keep coming off your Kubota. Replace a bad bracket or spring.

The hole in your bracket can wear and become larger. This can cause excessive vibration. Replace a worn tensioner bracket or spring.

Debris Interfering with Tension on Your Kubota Mower Belt

Keep your mower deck free of debris. When debris collects in your deck and under your tensioner, the tensioner may not be able to move freely to keep sufficient tension on the belt. When this happens, your belt is more likely to fall off the pulleys.

Keep your mower deck clean and free of debris. Not only will this help keep your deck components working well, it reduces the likelihood a small fire could start from the friction of the hot belt with dry debris on the deck.

Debris Collecting in the Grooves of Your Kubota Pulleys

Debris doesn’t only collect under your pulleys and cause problems, mud can pack in the grooves of your pulleys. Small objects like stones and acorns can also get stuck in the grooves.

When your mower is running around the pulleys packed with mud or debris, it must stretch to go around additional material. This can cause the Kubota belt to slip off the pulley or break. To avoid this, clean any debris you find lodged or packed in your pulley grooves.

Bad Bearing in Your Kubota Pulley

Now that you have checked your belts as the possible cause for having to continually reinstall your belt, you need to check your pulleys. A bearing in your pulley can go bad causing your pulley to not sit flat and parallel to your Kubota deck.

When the bearing is bad the pulley can shift causing the pulley to sit higher on one side than the other. This shift can cause your belt to slip off the pulley and come off your Kubota mower.

Check each pulley on your deck checking for extra movement when the pulley no longer sits securely on the deck. Spin each pulley by hand slowly. Feel for a restriction or bearing noise.

If you notice up-and-down movement, a restriction, or bearing noise, replace your pulley. This is an indication of a bad bearing.

You will be able to replace the bearings in some pulleys. A pulley and bearing assembly must be replaced in others because the pulley contains a sealed bearing.

Bad Bearing in Your Kubota Spindle Housing

A bad bearing in your spindle housing can cause movement in the blade making it wobble when it is turned. With your Kubota deck fully engaged, this wobble can become a serious vibration that can knock off your mower deck belt.

To check for a bad bearing in your spindle housing, start by putting on a good pair of work gloves to protect your hands. Gain access to the underside of your Kubota mower deck. Grab a hold of each side of a blade. Rock the blade up and down.

If your bearing is good, you shouldn’t feel any movement or hear a knocking sound. When you do hear a noise and feel movement, remove your spindle housings and check the bearing.

The bearing can be replaced in most Kubota spindle housings. There may be some models where you must replace the whole spindle housing assembly. Check out Kubota online parts diagram.

Have the model and serial number for your mower deck, not the mower, available so you get the right parts. Not feeling like looking up your own parts? Just call or visit your local Kubota dealer with this information for assistance.

Oil or Rust on Your Kubota Mower Belt

Your Kubota may develop an oil leak that can drip onto your deck and belt. Oil can cause your belt to slip off the pulleys. It can even cause your belt to swell when it remains on it for an extended period.

Find your oil leak and repair your oil leak. Clean oil off your deck and pulleys and replace your belt.

Rust can also affect your belt causing it to dry out prematurely. It will develop cracks and possibly break. When you find rust on the belt, clean your deck components to remove the rust. When the components are very rusty, it is best to replace them with new components.

Replace your mower deck belt with a new Kubota deck once your deck components no longer have rust on them.