6 Most Common John Deere Z425 Problems & Troubleshooting

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By Marvin Tucker

Farming Equipment

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The John Deere z425 is a zero-turn mower and the little brother of the JD z445. The two mowers share more or less the same speed, but the z425 is slightly less powerful.

These two turn mowers also share some issues regarding the engine, steering wheel, and safety switch.

On top of that, the z425 seems to have problems with the starting of the engine, PTO clutch, and some backfiring.

Since it can be pretty hard to choose between John Deere lawn mowers, let’s check the most common problems with the JD z425 and see if it’s worth investing in.

The Most Common Problems with John Deere Z425

This zero-turn mower from John Deere guarantees comfort and easiness of use while also being highly performative.

Being a small garden tractor, you cannot expect speed and performance to match that of a bigger John Deere model like the x590 or the 3025e, but we’re sure property owners will find something to love about this zero-turn lawn mower.

Compliments aside, this John Deere Eztrak mower is not without flaws.

Many users complain about starting and steering issues, and others have also encountered problems with the PTO clutch and the safety switch.

How serious can these problems become, and are these good reasons not to buy this riding mower? Let’s find out.

1. Engine issues

This is a reasonably broad topic because there’s not a single problem with the engine of this John Deere mower, but rather a group of issues related to the machine, and every user seems to experience a different one.

When you have engine issues, whether your lawn tractor doesn’t start, runs rough, overheats, or similar. Usually, we can narrow down the causes to clogged filters or fuel problems.

The fuel should be fresh, often changed (at least once every 30 days), the right type for your mower (don’t go cheap on this one), and the fuel filters should be cleaned or replaced regularly.

Aside from fuel filters, all the other filters of the system could provoke severe issues with time, especially air filters, so you should check regularly.

If your engine overheats, you might have a problem with the blades or the drive belt. They can come loose, or the height of the mower deck is too low.

2. Starting issues

As we’ve mentioned, if your engine has problems starting, it could be a filter problem, but it could also be that there is not enough fuel in the tank.

The tank doesn’t need to be empty to cause problems. Having a low fuel level can make your riding lawn mower struggle to carry out the most basic functions.

On top of that, you’d want to check the quality of the fuel. If there is debris or other strange particles, the filter will struggle to clean it, and the John Deere tractor will struggle to use it.

Replace the fuel filter at least once a year. If your mower rests in the garage during the cold season, detach the battery and charge it. Don’t leave the battery in the cold for long periods.

3. Steering issues

Having a loose steering wheel can be quite a problem and could also put the rider in various dangerous situations, so it needs to be worked on as soon as possible.

There can be different causes behind this problem, the most common being flat tires or tires inflated incorrectly or unevenly.

The steering shaft and support assembly might also be damaged or worn out. For example, the steering gear might get damaged if you hit a tree or a rock.

In many cases, you will need to replace the damaged part, but luckily this is something you can do by yourself if you have some basic repairing experience.

If not, you can always refer to your John Deere dealer.

4. PTO clutch issues

This clutch transfers power from the engine to the blades, so running your John Deere lawn tractor is essential.

If the zero-turn mower is new, long working hours can quickly overheat the clutch, causing issues.

The clutch might also slip and disengage, which is often the most common occurrence with the John Deere z425.

In this case, you will hear a screeching sound when you activate the PTO. Disengage it, turn off the mower and remove the key before attempting any inspection.

Don’t ever inspect the mower deck if the blades are spinning, the mower is turned on, or the PTO is still engaged.

There may be something that prevents the blades from turning. Otherwise, a safety switch may be somewhere preventing the clutch from engaging.

5. Safety switch issues

We’ve seen what happens when the safety switch turns on at the wrong time, but it might also happen that the same switch deactivates for no apparent reason.

The safety switch must remain on because it is meant to keep the rider safe. Many users look for ways to bypass the safety switch on a lawn mower, but we do not recommend this practice.

However, if the switch malfunctions and cannot be reactivated, there’s no choice but to replace it.

Usually, there are two main safety switches on a John Deere mower, and you can find the type and location on your John Deere manual.

Be sure to park the mower on a flat surface, turn it off and remove the key before you attempt to troubleshoot any safety switch.

6. Backfiring issues

An engine backfires when the fuel mix is too lean since there is more air than fuel, and thus, the combustion is unbalanced.

This unproportioned mix can disrupt the timing of the combustion chamber, and as a result, the spark happens outside the chamber, provoking small explosions.

That’s why when your engine backfires, you hear loud bangs, and if there’s too much fuel, you might see emissions of black smoke.

Backfiring can be either fuel-related or engine-related.

If it’s fuel-related, you might have low pressure in the fuel pump, which will need to be replaced and the fuel filters cleaned.

If the issue is engine-related, adjusting the engine may be the answer. If not, you should examine the fuel filters and the spark plug. Replace them if they need to be repaired due to wear. 

John Deere Z425 problems: are they a deal-breaker?

No, most property owners are happy with this excellent garden tractor. Of course, this isn’t the only reason you should trust this model from John Deere.

It seems that the most common issues with the z425 are problems that you can encounter with most lawn tractors and involve the mower parts most commonly affected by lack of lawn care.

Indeed, maintenance is fundamental to keep your John Deere lawn mower in good shape for as long as possible, but many users forget to do regular check-ups on their tractors.

This might not seem like a big deal at first, but more minor problems quickly lead to bigger ones, and before you know it, you’re emptying the bank trying to fix your riding mower.

So next time, before you contact your John Deere dealer or your local mechanic, do a complete check-up to see if there’s anything that needs maintenance. You will spare a lot of money and add many years to your lawn mower lifespan.

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