How to Adjust Belt Tension on Riding Lawn Mower

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Riding mower belts play a critical role in keeping your mower operating smoothly. 

That’s why it’s so important to ensure proper tension in your unit’s belt at all times.

Let’s face it: insufficient belt tension can have a drastic domino effect that could do damage to other pivotal parts, for example, the tension idler pulley.

In truth, you don’t want to have too little or too much tension as both can cause a variety of problems including eventual belt damage.

The idea is, therefore, to find a sweet spot between the two extremes and adjust the belt tension appropriately.

Learn how to adjust belt tension on riding lawn mower to keep your lawn mower operating flawlessly, summer after summer below.

How to adjust belt tension on riding lawn mower

Obviously,   the exact steps may vary depending on your riding mower’s make and specific model so check your owner’s manual before you begin the procedure. 

However, the steps we outline below are generally to be followed when adjusting belt tension on most riding lawn mowers: 

How to adjust belt tension on riding lawn mower- step by step guide

Preliminary steps

  • Drive your riding lawnmower to a surface that is flat and level. Your driveway or the garage floor could be the perfect working surface. Drive there and park.
  • Since you don’t want it to roll or shift while you tighten the belt, place concrete or wooden block in front as well as behind its rear wheels.
  • Next, engage your riding mower tractor’s parking brake.
  • Now remove the ignition key from its ignition switch.
  • Lastly, disconnect the spark plug- simply pull the wire off of the spark plug. 

Safety Tip: Allow the tractor’s exhaust system to properly cool down before you attempt to detach the spark plug wire. A hot engine can, of course, burn you.

With these precautionary measures in place, you can proceed to work while safe in the knowledge that your mower won’t start or move accidentally. 

Now follow these steps:

1: Access the drive belt

Start by locating the mower’s main frame tube. Then unbolt the clamp bolts here with a wrench.

An alternative tool that you can use to loosen the bolts is your pair of pliers.

Depending on the specific model you’re working on, you may need to remove the drive belt cover- simply slide it off of the mower’s deck to access the belt.

Quick Tip: The only way to gain access to the belt in some makes of riding lawnmowers is by removing the deck- the instructions on how to remove the cutting deck should be found in the Operator’s Manual (check the “Service” section).

2: Tighten the belt

As mentioned, the proper way of tightening the belt will vary from one model to the next.

For example, for MTD riding mowers, the recommended way to tension the belt correctly is by working on the idler pulley as the tension spring that maintains proper stress on the belt is located here.

Likewise, belt drive tension problems in Troy Bilt riding mowers are usually resolved by adjusting the deck level. 

Nevertheless, the following steps will apply for most models: 

Loosen the cap screw – it is usually found at the center of the pulley- and adjust it appropriately. This is how the length of the belt in some riding lawnmowers is adjusted.

To tighten the belt, change the location of your unit’s main frame (inside the clamps) to a position that makes it tighter.

In some models, you improve the tension by manipulating and adjusting the length of the belt from the transaxle pulley.

Still, there are riding mowers in which the only way to tighten it is by pulling the front frame assembly more forward by hand until you attain sufficient tension.

3: Replace the removed parts

Replace the drive belt cover and the clamp bolts.

Next, reconnect the spark plug and start the mower to test if the belt is now stiff enough for proper operation. 

Repeat the above steps to re-adjust the tension if necessary until you’re satisfied.

A word on Craftsman riding lawn mowers

Craftsman lawn mowers do not come with manual adjusters for drive belts.

For this reason, your only remedy when the belt becomes loose and starts to slip is installing a new deck belt.

The procedure for installing blade drive belts may vary to some degree for each Craftsman riding mower model, so again refer to your particular Craftsman mower’s owner’s manual.

Useful tips

How to identify the belt

It is easy to recognize a drive belt in riding lawnmowers- it is typically a rubber-made strong band/strip (black in color) and it’s usually between 3/8 and 5/8 inches wide.

Signs that the belt is loose

If the mower’s drive belt has become loose, it will often slip when:

  1. The tractor is going up a hill/an incline.
  2. The mower is towing a heavy load around the yard.

The other telltale sign of a loose belt is the unit refusing to drive forward or slowing down when you’re driving uphill.

Take it to a service center

If the issue persists, it is important to have the mower inspected and repaired by an authorized service center. 

Most manufacturers maintain a directory of authorized service centers for their equipment – visit it and check if there is a local repair service that is listed.

Final words

Even after learning how to adjust belt tension on riding lawn mower, it is important to remember that all belt issues are not as a result of inadequate tension- your belts may be worn or seriously damaged and in need of replacement. 

Replacement belts are typically available from your local riding mower brand dealer and are straightforward to install- you often need a screwdriver and a little elbow grease.

One last thing: After adjusting the drive belt to proper tension, check around and see if anything else might need attention- a bearing may be obstructed, the pulley may be wearing, etc.

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