Craftsman Riding Mower Belt Keeps Coming Off

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The reason your Craftsman riding mower belt keeps coming off might be as a result of a defective belt keeper, loose mower belt, debris interference or loose pulleys.

Fortunately, these problems can be easily identified and solved by following the right guidelines.

In this article, I reveal common reasons why your Craftsman riding lawn mower belt may continue to come off and troubleshooting tips to help solve the problem. 

Reasons Your Craftsman Riding Mower Belt Keeps Coming Off

Some of the reasons why your Craftsman riding mower belt might continue to come off include:

  • Defective belt keeper
  • Loose or Worn deck belt
  • Defective bearings in the pulleys or spindle housings
  • Oil and rust on the belt
  • Worn idler tensioner bracket

Tools You Need For This Job

Some tools you may need to diagnose and fix your mower belt include:

  • Vice grips
  • Hammer
  • Safety/work gloves
  • Screwdrivers
  • An adjustable wrench
  • New belt
  • A set of pliers
  • Woodblocks

Craftsman Riding Mower Belt Keeps Coming Off: Possible Causes and Fixes

1. Loose or Worn Belt

The belt of your Craftsman riding mower can be worn because it is loose. In this case, it becomes worn or stretched from normal use.

Diagnosis

When the belt becomes stretched or worn from normal use, it indicates that it is loose and requires replacement

Fix

Replace the worn or loose belt with a new one. 

2. Shredded Belt

A shredded belt can become weak and may break, causing the belt to come off the deck of your lawn mower. Furthermore, an improper belt installation can also cause it to shred. 

Diagnosis

  • Inspect the edges of your belt for signs of shredding and check if your deck belt is properly routed around your pulleys.
  • If the belt is correctly routed, check if the part of the belt guide makes contact with your belt.
  • A shiny or smooth spot on the metal can also indicate that the belt is shredded.

Fix

  • After getting the area that is causing the belt to shred, adjust the bracket or keeper properly to prevent the belt from rubbing.
  • Replace the shredded belt after putting the keepers and brackets in their proper positions. 

3. Defective Belt Keeper

The function of your belt keepers is to guide the belt to keep it in place. They can become bent or move out of place if the belt snaps or there is a lot of slack in it. 

When the belt is slack it can hit and bend your keepers, causing the mower belt to come off your pulley.

Diagnosis

  • If you notice that the belt keeper is not in place or it is bent, it means that it is defective.

Fix

  • Use a vice grip or hammer to adjust the mower’s belt keepers so that they can sit 1/8-1/4 inches away from the mower’s pulley. 

4. Defective Bearings in The MTD Pulleys or Spindle Housings

Defective bearings in the pulleys or spindle housings may be one of the reasons why your deck belt keeps coming off. 

Ensure that you check each one of your pulleys and see if they are running parallel and flat to the mower deck.

The pulleys shouldn’t be sitting higher off the deck on one side than the other. 

If they are not running flat, the deck belt can slip off the pulley. This means that there is a defective bearing in the pulley.

The problem may also arise from the spindle housing assembly. An issue with the spindle housing can cause your Craftsman mower to vibrate and knock the deck belt off the pulley.

Diagnosis

  • Check the idler pulley for any bad bearing. The mower’s idler pulleys come with a sealed bearing and this requires the entire pulley to be replaced.
  • To get a failed bearing in the housing, grab a hold of each side of the blade and make sure that you wear a pair of work gloves to shield your hands from the sharp mower blades.
  • Grip both ends of your mower blade and rock the blade in an upward and downward position to check for noise or movement. 

Fix

  • Replace the entire pulley to fix the issue of defective bearings in the pulleys.
  • Take the spindle housing apart and inspect for a defective bearing. Some spindle housings are sealed and require the entire assembly to be replaced while others can be rebuilt. 

5. Using The Wrong Craftsman Mower Belt

This is also one of the reasons why your deck belt can come off. Failure to use the ideal belt for your mower can pose problems and safety concerns.

Diagnosis

  • Inspect the belt if it is the right one for your Craftsman mower model

Fix

  • Ensure that you confirm the part number for the replacement you purchased matches the one listed in the “replacement parts” section of your MTD mower manual.

6. Idler Tensioner Bracket or Spring is Worn

The bracket can hold idler pulleys in line. If the spring is weak, it may cause your deck belt to come off.

Furthermore, the bracket’s bushing may become worn if it is not well greased. The pulley will run at an angle instead of running flat. This can cause your Craftsman riding mower to vibrate.

Diagnosis

  • Locate the pulley on one side of the bracket and the spring on the other side.
  • Check the bracket’s bushing if it is worn or not well greased. 
  • If the spring appears weak or the tensioner bracket (where the spring attaches) is worn, it needs replacement.

Fix

  • Grease the idler bushing.
  • Replace the spring.
  • Replace damaged or worn parts of the tensioner bracket

7. Rust or Oil on Your Craftsman Riding Mower Belt

An oil leak may cause oil to get on the belt and can result in belt slippage on the pulleys.

Old brackets and pulleys may develop rust that can get on the deck belt. This causes the belt to break, dry out or crack.

Diagnosis

  • Check for signs of rust pulleys.
  • Check for signs of cracks and wear on the belt. 
  • A low oil level may indicate that you have an oil leak.

Fix

  • Replace rusty pulleys and inspect the oil level before carrying out mowing operations.
  • Replace the mower belt if you notice signs of wear and cracking.

8. Debris in the Grooves of Your Craftsman riding Pulleys

The grooves in the pulleys collect mud or debris that can cause the belt to come off your lawn mower.

The pulley’s material may also cause the belt to stretch and this will allow it to snap or roll off the pulley.

Diagnosis

  • Take a look at the grooves in the pulley and check for items (such as debris and mud) that are stuck in the area.

Fix

  • Examine the grooves in the pulley and take off any items that may be stuck in this area.

9. Debris Interfering with Proper Tension on The Craftsman Riding Mower Belt

Your mower belt can become loose and come off the engine as a result of debris build-up. The accumulation of debris on your deck can cause the tension pulley not to move.

This means that there won’t be proper tension on the belt, causing the deck belt to come off. 

Diagnosis

  • Check the mower deck for debris.

Fix

  • Ensure that the deck is clean. 

10. Craftsman Deck Belt Breaks or Gets Heated Up

This is one of the problems why your Craftsman deck belt may come off. If the belt breaks, it will come off the mower deck.

Diagnosis

  • If you detect unsatisfactory cuts, turn off the engine of your Craftsman riding mower and check the mower deck carefully for any sign of belt breakage.

Fix

  • To fix a broken belt, you need to clean your mower deck, adjust the pulleys and replace the belt.

11. Extreme Weather And Temperature Can Cause The Belt To Come Off

Your Craftsman riding mower belt may keep coming off in extreme temperature changes. This issue is very common in very cold climes.

The reason is that the belt loses its shape in cold weather. If you continue to operate the mowing machine with this problem, It will produce cracks on the belt and break it.

Diagnosis

  • Check for cracks on the belt to know if the belt is damaged. 

Fix

  • Do not operate the mower in extreme temperatures and weather. 
  • Replace the cracked belt with a new one.

12. Loose Pulleys

The belt connects a series of pulleys in the mower deck, which enables the mower blades to engage and spin.

If the pulleys are loose, the entire system would be compromised if the pulleys become loose in their positions.

Diagnosis

  • Check the pulleys if they are not loose in their positions
  • Examine other parts of the pulley-belt system. If the parts are damaged or lost over time, it means that the pulleys are loose and the mower belt won’t stay in place.

Fix

  • It is advisable to seek the help of a trusted mechanic that can check the Craftsman riding mower for defective or missing rear hanger clip pins and draft rods.

How to Put a Drive Belt on a Craftsman Riding Lawn Mower

Here are some tips on how to put a belt on your Craftsman riding mower:

Step One: Get the Required Tools

When you want to replace the belt on your Craftsman riding mower, you need to get the required tools for the work.

These tools include screwdrivers, woodblocks, an adjustable wrench, a set of pliers and safety gloves. 

Do not forget to get the ideal belt for your mower and also examine the condition of your crankshaft and pulleys. 

Step Two: Place Your Mowing Machine On a Smooth Surface

Position your mower on a level and level surface before you begin the belt replacement process. Apply your parking brakes while keeping the transmission in gear.

Using the parking brakes will prevent the mower from rolling. It is also important to disconnect spark plug wires before putting in a new belt. 

This is to prevent the mower’s unintentional starting while working on it. Ensure that you also put on work gloves to protect your hands and put off the ignition switch.

If you want to take off the mower deck during this process, it is important to set the cutting deck to its possible lowest position.

Step Three: Take Off the Cutting Deck

To set your deck to its lowest point, you may need to place the deck on the height adjuster. 

You should locate a bolt on the rear section of the deck (near the mower’s tire) and the bow clips that are above the bolt.

Take the bow clips. Furthermore, push the deck lever towards you to help disengage your mower blades. The drive lever is located at the side of your steering wheel.

Roll the engine’s blade belt off to release the drive belt from the belt keepers. 

Take off the pin and suspension arms on both sides. Detach the washer and left suspension arm retaining clip and unfasten it.

After that, remove the left rear deck bracket clip to pull the bracket from the mower deck. You can also repeat the same procedure to remove the right rear bracket and right suspension arm.

After you have taken off the left and right suspensions, rear brackets and arms, you can pull out the mower deck and check the cable of the blade that is secured to your mower deck.

Step Four: Take Off the Old Drive Belt

Release the mower’s locking tabs and pull out the deck bracket’s cable. Disconnect the blade cable spring and move this cable aside. Make sure that the old wire is free of connections.

Do not use the lever until you have reinstalled your Craftsman riding mower deck. Loose the pulley around the old belt and remove the belt from the pulley with your hands. 

To take off the drive belt, you need to shake the pulley and guide. Similarly, detach the Craftsman drive belt from the second pulley

Step Five: Insert A New Craftsman Drive Belt

Take your replacement belt and slide it up and around the engine pulley. 

To slip a replacement belt between the guide and pulley, you need to mount it on a mandrel pulley with a big belt keeper. Carefully work it down onto the pulley with your hands.

Make sure that the new drive belt fits the pulley grooves properly and that it does not lag. In the same way, ensure that you wrap the belt around your mower’s idler pulley.

Make use of the hands to move the pulleys and ensure that they move without restriction.

Step Six: Reinstalling

You can now reinstall your deck after putting on the new Craftsman riding mower drive belt. 

Connect the blade clutch cable spring to the idler arm by pushing the cutting deck toward the frame. Push the blade clutch retainer into the deck bracket to engage the locking tabs.

The front link support should be reconnected in the same way you detached it. This will be a reverse form of the above procedure. Reconnect the deck brackets and left and right suspension arms carefully.

Ensure that you take the blade belt through the belt guides and roll it onto the pulley of the engine. 

This pulley will be the third one. Ensure that you inspect the lubrication and connections of the mower’s blade belt.

If it requires adjustment, make the necessary adjustments to ensure that the blade belt is properly routed through all of the pulleys and belt keepers. Make sure that you reconnect the spark plug cable and also lower the hood of your Craftsman riding mower.

Engage your mower blades by pushing the drive lever. Turn on the mower and inspect if the blades are moving freely and if the sound of the engine is okay.

How to Extend the Lifespan of Your Craftsman Riding Mower Belt

Here are some tips to follow to elongate the life of your Craftsman riding lawn mower belt:

  • Replace damaged belt keepers or brackets.
  • Always clean your Craftsman riding cutting deck after mowing to get rid of debris.
  • Inspect the spindle housings and pulleys for bearing failure at periodical intervals.
  • Keep rust and oil from forming on your belt.

Conclusion

Your Craftsman riding mower belt may continue to come off because of worn or loose belts, loose pulleys, oil and rust on the belt or defective belt keepers.

Read the recommended troubleshooting tips to get your riding mower working efficiently again. If you have tried the tips shared here and the problems persist, it is best to seek the help of an expert to solve the issue.