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How to Adjust Belt Tension on a Riding Lawnmower, step by step

Have you ever experienced your riding lawnmower not properly mowing? Or leaving untrimmed lawn patches? The problem may be a loose drive belt. Luckily, the solution is pretty simple, and just a socket wrench is all you’ll need for the modification. If you’ve never undertaken this type of lawnmower maintenance before, don’t worry. We explain this information in a step-by-step procedure for you.

How to adjust belt tension on a riding lawnmower, step-by-step:

  • Step 1: Test your current lawnmower drive belt’s tension.
  • Step 2: Examine the components such as the pulleys, belt, spring, and swingarm on the mower and search for any damage.
  • Step 3: Remove and pull back the clamp holding the cable to stretch the spring connected to it. 
  • Step 4: Start the engine and pull the blade engagement lever to monitor the belt operation after adjustment.

The drive belts connect the engine’s driveshaft to the transaxle pulley and transmit the torque and power to the cutting blades. In the case of riding lawnmowers, it lies underneath the mower deck. After prolonged use, the belt quality usually degrades. They have been known to become loose with time due to the elongation in their tensile cords. The solution is usually a replacement. However, you can always adjust the belt’s tension when the elongation is not very substantial, and we look at that in this article.

The article deals with all necessary steps to tighten the drive belt for a riding lawnmower. A quick explanation of some common questions asked about drive belts and lawnmowers is also provided. Stay tuned. 

Adjusting the Belt Tension on a Riding Lawnmower, step-by-step:

The steps below can help you in adjusting the tightness of a riding lawn mower drive belt.

● Step 1: Access the current belt:

Before we dig into it, we first have to see if the current drive belt is worth tightening. Most riding lawn mower models have a blade engagement lever beside the steering wheel. The lever pushes the blades in contact with the grass once the cutting deck is lowered on the ground.

To see whether your current drive belt has the right tension, start your engine and raise the throttle lever to the maximum. Next, press the lever up to engage the cutting blades. If you observe the blades cutting immediately after the lever is pushed, it means that the drive belt is tight enough. On the other hand, if a whirring sound is observed right after you push the lever, it means that the drive belt is slipping and needs to be adjusted.

● Step 2: Inspection of the mower deck: 

We now know that the drive belt is slipping. To troubleshoot our problem, let us first begin inspecting the mower deck and its components. Pull the blade engagement lever and lower the mower deck as much as it can be.  The following components must be assessed:

Belt: Ensure your drive belt is intact and that chunks and cracks are not to be seen. Please change it immediately when it appears damaged.

Swingarm: On the swingarm, pulleys and springs are mounted. At one end, the arm is pin connected, and at the other end, it is free to rotate.  Ensure the arm rotates freely. If it doesn’t, drop some oil at its pivot and clean any debris that might be preventing it from rotating freely.

After the above components are operating correctly, press the lever again to unlock the blades.

Spring: The cable that arrives from the lever is attached to a spring. Touch the spring and see if it’s perfectly stretched or loose. Touch your belt and notice if it feels loose at the same time. If so, we can proceed to the next stage and adjust the tension of the belt.

Step 3: Tighten the belt with a cable adjustment:

After you saw a loosening belt, lock the blade lever again. You must have noted the wire coming from the blade lever connected to the springs is attached to a bracket on the deck.

On the bracket, loosen the bolts and pull the wire back towards you. Tighten the bolts and see if the string is stretched as well.

● Stage 4: Testing the tension in the new belt:

Start your lawnmower engine at full throttle after the bracket has been pulled back. Press the blade control lever up and notice the cutting activity of the blades immediately. When the blades start to cut almost instantaneously, the tension of the belt is optimal. However, if the belt remains loose enough, this technique did not add the requisite tension, and you should consider replacing the belt.

Related Questions:

1. How to replace the drive belt on a riding lawnmower?

In situations where tightening the drive belt does not make any difference, replacement is the imminent solution. The steps that should be followed for replacing the drive belt on a lawnmower are given below:

Step 1: Disengage the spark plug wire

To start, turn the ignition switch off and remove the key. Afterward, lift the hood of your lawnmower and detach the spark plug wire. This step should be followed as a safety precaution.

Step 2: Disassemble the mower deck

This step involves removing the mower deck from the main body.

– Step 2.1: Pull the mower deck down:

Push the blade engagement lever to lock the blades and lower the mower deck down to the ground.

– Step 2.2: Take the belt off

Take the drive belt off from the engine pulley that is connected to the drive shaft. Also, release the belt holders.

– Step 2.3: Disconnect the deck from the main body.

The mower deck needs to be detached. To do this, remove the supports connecting the deck to the mower body from both sides of the deck. This step includes removing all the retaining pins and washer supports from the suspension arms, lift links, and rear end brackets. Note that this detachment needs to be done from both sides of the deck once everything is removed. The deck comes off.

Step 3: Detach the old belt

– Step 3.1: Take a snapshot

Note the layout of the belt passing through the pulleys and its positioning on the deck. Document the routing by taking a photograph on your phone.

– Step 3.2: Take the old belt off

Take the belt off from the three pulleys. There are two mandrel pulleys and one idler pulley that wrap the belt around them.

Step 4: Connect the new belt

Install the new drive belt by passing it around the mandrel pulleys and the idler pulley. Make sure you also pass it through the belt keeper. Now, push the mower deck under the lawnmower to make the connections again.

Step 5: Reattach the mower deck

To reattach the mower deck, connect all the supports, including lift links, rear-end brackets, and suspension arms on both sides of the deck. Secure the linkages using washers and retaining pins. Connect the belt to the engine pulley. 

With everything fixed, raise the mower hood again to connect the spark plug. Insert the key in the ignition switch. Start your lawnmower.

2. How long is the drive belt on a riding lawnmower?

Drive belts are responsible for transmitting power from the engine shaft to movable parts in the mower, such as the blades. Most riding lawn mower models comprise primary and secondary drive belts. Both belts have a length varying from 42-55 inches based on the individual model.

3. Why does the belt keep falling off the lawnmower?

The drive belt of your lawnmower can fall off for different reasons. The exact causes depend on your machine’s model. However, some general causes result in this issue, and they are given below:

– Defective components:

If they’re not working, the driving belts and idler pulleys can affect the belt’s working. Besides, the swingarm must rotate around its pivot easily. You have to examine the adjustment of the mower deck. The front of the deck is usually lower 1/8 to 1/4 inch for normal conditions than the back. The belt begins to slip away at a pitch more significant than this.

– Buildup of debris:

The accumulation of dirt between the pulley and the bracket can also decrease the friction of the belt. Make sure the driving belt is not covered with dirt, grass, or stick.  This condition is imminent under harsh operating conditions and low maintenance.

4. What are the two basic drive belt shapes used?

The drive belts can be of V-type or synchronous design. V-belts have a cross-section in wedge-shaped form. The only force that holds the belt together is friction. On the other hand, synchronous belts have a notched profile identical to the gears along their inner circumference. They are generally attached to gears and are typically used in timing operations.

Final comments:

Maintenance of the lawnmower belt would be one of the most common cases, mainly if it were not adequately maintained in the past. We recommend that you clean your lawnmower from time to time and check the deck components thoroughly to see if they are operating correctly. Besides, when making the belt replacement, you should always check the manual of the manufacturer. It is better to take precautions when making these changes so that your lawnmower does not start accidentally.