Zero Turn Mower Weak On One Side

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Zero-turn mowers are extremely maneuverable and have a very small turning radius. This means you can use a zero-turn lawn mower to cut grass close to barriers more easily and quickly. 

One of the most common problems with these mowers is that one side becomes weak. A riding mower that is continuously tugging to one side can be quite exhausting. 

In this article, I talk about common reasons why your zero-turn mower is weak on one side, outline steps you can take to diagnose the problem, and simple fixes to get your zero-turn mower performing at an optimal level again.

Why Is My Zero Turn Mower Weak On One Side?

The reasons your zero-turn mower is weak on one side may include:

  • Insufficient tire compression on one side
  • Airlock in the hydrostatic motor
  • Displaced freewheeling rod
  • Lack of traction on one side
  • Alignment and motor tracking out of sync
  • Dragging drum brakes
  • Inadequate weight balance
  • Clogged hydro oil filter 

Tools You Need For This Job

Some tools you need to have nearby when troubleshooting include:

  • Work gloves
  • Screwdriver
  • Pliers
  • Socket wrench set
  • Jack
  • Tire pressure gauge
  • Tire pump
  • Penetrating fluid
  • Clean rag

Zero Turn Mower Weak On One Side: Causes, Diagnosis, and Fixes

1. Insufficient tire compression on one side

A deflated tire on one side of your zero-turn mower can cause it to get weak on that side. The mower may pull toward one side if one of its tires has less air in it than the others. 

This is also true for the front tires on some riding lawn mowers. If one is uneven as a result of not being properly filled, it may cause the mower to lean to one side.

Diagnosis:

Check the recommended minimum tire pressure(PSI) for your mower. Then, use a tire pressure gauge to check the PSI for each tire. 

If the PSI produced by any of the tires is less than the recommended value, the tire lacks compression.

Fix:

Inflate the tires to the recommended PSI. You can do this at home using a tire pump or at a gas station with a free air compressor.

Most gas stations have manual air pumps installed so you can check and keep an eye on the PSI of your tire while also adding air to it. This will stop you from exceeding the recommended PSI.

2. Airlock In The Hydrostatic Motor

Zero-turn mowers use two independent hydrostatic pumps to power each side. An air lock or cavitation can occur in one of these pumps, leading to a weak drive/control on that side.

The pump’s pressure and the movement of the oil are what power hydrostatic drives. Air has little force and diminishes traction. If air enters the hydrostatic motor, it will begin to lose power on one side.

Air could enter the hydrostatic motor via a leak or a loose connection. Oil cavitation can also cause air bubbles to form in the hydrostatic system during high temperatures, resulting in an airlock.

Diagnosis:

You will notice that your hydraulic system has been contaminated with air if it is shifting slowly from one speed to another for no reason.

Fix:

Purge the hydrostatic system to get rid of trapped air in the pump.

3. Displaced Freewheeling Rod

The freewheeling rod helps to control the movement of the motor on each side.

A freewheeling rod that is displaced or stuck may cause movement difficulties on one side of your zero-turn mower.

Diagnosis:

Check the freewheeling rod. If it is displaced or stuck, it may be the cause of the problem.

Fix:

Reinstall the rod correctly if displaced. You can use a penetrating fluid to free the rod if it is stuck.

4. Clogged Hydro Oil Filter

Most zero-turn mowers make use of two hydrostatic fluid filters – one located on each pump. The oil filter sifts the hydrostatic fluid that facilitates movement.

If the filter gets clogged on one side, the oil supply will be reduced greatly. As a result of this, the mower may become weak on that side.

Diagnosis:

Check the filter on the weak side of the mower. If it is dirty or blocked, it could be the culprit.

Fix:

Replace the clogged filter with a new one.

5. Lack Of Traction On One Side

Zero-turn mowers are driven by belts that are powered by an engine and clutch. The belt can be split or damaged causing reduced traction on one side.

Grass or dirt buildup on the belt and pulley system can also reduce the traction on the drive belt. The pulley may be stuck or damaged and this can lead to weakness on one side of the mower.

Diagnosis:

Inspect the belt that rotates the pulley on top of the transaxle. If it appears to be worn, glazed, or contaminated with oil, it is damaged and could be reducing traction.

Check the deck, pump, and pulley system. If you notice grass or dirt build-up, it could be affecting one of the pulleys or drive belts.

Fix:

Replace the belt if it is glazed, shiny, or damaged.

Clean the deck and pulleys and replace any stuck or broken ones that could be causing belt damage or wear.

6. Alignment And Motor Tracking Out Of Sync

The movement of the two sides of the mower should always be in sync. Handlebar movement, alignment, and the tracking rod attached to the hydrostatic motors are used to track the two motors. 

Essentially, this means that the left and right sides of the mower controls should be replicas of one another. A disorder of this alignment may cause problems on one side of your zero-turn mower.

Diagnosis:

Check how the handlebars align and move as a unit. Pull the bars together to see if they align, then fully advance the bar to observe if they align while the engine is off. You will need to make adjustments if you discover that they are out of alignment.

If they line up, you should also check under the mower. A link rod connects the handlebar to the motor. The rod moves the plate into the hydro motor as you move the handlebars. The placement of both plates must be equal. 

Finally, steer the lawnmower in a straight line and watch the handlebars to see how they align. If the movement is not in sync, there is a problem with the alignment.

Fix:

Adjust the alignment through the link rod and drive bars. Also, check for any loose screws in the link rod and tighten it.

7. Dragging Drum Brakes

Your zero-turn lawn mower is equipped with two drum brakes, one on each wheel. These drum brakes are utilized in conjunction with your mower’s parking brake mechanism.

One brake may not release as fast as the other, or the brake caliper on one side may be frozen making the mower pull to one side.

The brake can also drag or rub, creating the impression that one side is weak, as a result of issues with the drum itself or the brake engagement mechanism.

Diagnosis:

  • Choke the front wheels, disengage the hydros, release the brake, and jack up the back of the mower to lift the wheels off the ground. 
  • Spin the wheels to see if there is a difference in resistance. The wheel on the weak side should be more difficult to turn.
  • To examine the brakes themselves, a tire will need to be removed.
  • Remove the tire and examine the brakes for any physical damage.
  • Check the springs, the shoes, and the adjustment screw.
  • Replace damaged parts and replace the brake shoes if they are worn.

Fix:

  • Replace damaged components and replace the brake shoes. 
  • After that, spin the wheel to ensure that there is no resistance. 
  • Regulate the shoe adjustment screw if there is resistance, it should not be too tight or loose.

8. Inadequate Weight Balance

Your zero-turn mower may have a weak left or right side due to the weight of the load it is pulling or carrying.

If you have a bagger or any mower accessories, your riding mower may pull to one side if the weight is not evenly distributed. 

Diagnosis:

Remove all of your mower accessories and run the mower without them. If the issue is resolved, you can be certain that the attachment was the cause. 

Fix:

Make sure that your equipment isn’t completely skewed to one side.

If the equipment is too heavy for the mower or tends to shift to one side, consider replacing it or using a smaller alternative.

What Majority Of Users Feel About Zero Turn Mowers

Zero-turn mowers are more expensive than riding mowers, but they cut your grass more quickly and effectively, making it worth the price.

The maximum speed of an average riding mower is about 4 MPH, while the maximum speed of a zero-turn mower is about 8 MPH. 

They are wonderful and extremely quick over very broad, flat lawns. They are also perfect for cutting around bends and carriers as a result of their small turning radius.

Conclusion 

A zero-turn mower that is continuously pulling to one side, forcing you to struggle to keep it on track while mowing, is one of the toughest issues to have to deal with.

I have talked about the causes of this issue and given solutions to each of them in this article. Follow this guide to troubleshoot and apply the recommended fixes to resolve this problem.