7 Mountfield Lawnmower Problems and Solutions

Mountfield lawnmower

Despite a few common problems that your lawnmower may have, Mountfield lawnmowers are trusted because they are compact, lightweight, and easy to handle.

These ride-on lawn mowers are equipped with ample power from the Stiga engine, and the raised seating offers superior sitting visibility — which is suited for mowing for longer hours.

As a Mountfield lawnmower, there are a few common problems that you should be aware of.

These include the blade bosses shearing off, broken shear key, and gas tank or gas line blockage.

Read on to learn how to troubleshoot these common problems and find the solution to your problem.

Here are some of the most common Mountfield mower problems:

1. Blade bosses sheared off

If your Mountfield lawn mower blade bosses sheared off, you are not alone.

This common problem affects many mowers and can be very costly. However, there is a solution for this problem that is very affordable and easy to install.

A new blade boss is an inexpensive and simple solution to this problem. You can purchase them from most dealers online.

The installation process is simple and involves tightening the blade bolt to the correct torque setting.

Alternatively, your local dealer should be able to help you install a new boss.

If you are unable to remove the old blade bosses yourself, you can purchase a push mower blade replacement kit. These kits are cheap and easy to use, and they include replacement nuts and blades.

They can be found at home improvement stores for a few dollars. If your blades have already been damaged, you may have to replace them all.

A new set of blades will usually cost just a few dollars, and you can reinstall them in less than ten minutes.

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2. Gas tank or gas line blockage

If you’re experiencing problems starting or running your mountfield mower, it’s time to diagnose the problem.

There could be several reasons for this problem, including a dirty gas tank or blockage. A fuel filter may be clogged or the fuel line itself is obstructed.

While the task may not be huge, it’s important to follow safety precautions when working with your lawn mower.

A damaged carburetor can also cause the engine to hydro-lock. Hydro-locking occurs when gas in the cylinder prevents movement. This can cause a no-start condition, so make sure to use a fuel stabilizer when transporting your mower by trailer.

The fuel stabilizer will prevent this problem while winterizing your Mountfield mower and recommissioning it in the spring.

If the fuel tank is cracked, it’s most likely the result of a malfunction. A low-hanging shrub branch or other object may have fallen on the lawnmower and damaged the tank. In the worst case scenario, the fuel line could snag on a shrub and break off.

Luckily, replacement of a fuel tank can be a simple process. The fuel line on your mower is typically held in place by spring clamps.

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3. A clogged carburetor

To start troubleshooting a clogged carburetor on a mountfield mower, you must make sure that you have a good understanding of how to inspect a carburator. First, make sure that you check the level of oil.

You should do this every time you mow, or at least once a month, depending on the frequency of use.

Check the oil level regularly as well, since oil consumption can be much higher on sloped ground or if the oil blows through the crankcase breather. If you’re having trouble starting your Mountfield mower, it’s likely the carburetor is clogged.

Another problem that could be causing a clogged carburetor on a Mountfield mower is the choke.

This is a part of the lawnmower that mixes air and fuel for combustion before entering the engine. The carburetor has several passages, depending on the throttle position.

The idle circuit is the passage that allows fuel to enter the air stream while the mower is in idle mode.

When you are running on full throttle, fuel enters the main jet. The choke helps to provide extra fuel during start-up and during cold conditions.

If you can’t find the problem, you may need to replace the entire unit. The float and the bowl are both located underneath the carburetor.

When you apply a voltage to the coil, the solenoid will open the valve and allow fuel to enter. But be careful, because they can get stuck and clogged.

Regardless of the method used, it is essential that you check your carburetor before starting your mower.

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4. Broken shear key

If you notice that your shear key is not releasing the blade, you might have broken the shear key on your mountfield mower.

This can happen for several reasons. Sometimes it happens because the mower has been in storage for some time.

Occasionally, this may be the case and you need to take it to your local dealer to repair it. Broken shear keys on Mountfield mowers are quite common, but it’s still important to know how to fix them in case you break them.

A broken flywheel key is one of the most common causes of poor running or no-start problems in lawn mowers. A faulty flywheel key is caused by a mower striking a non-mowable object.

The crankshaft is solidly connected to the cutting blade, but if the mower hits an obstacle, the crankshaft could become broken.

A faulty ignition module or a malfunctioning safety interlock system can also result in a broken flywheel key.

5. Oil level

If you notice that the mower doesn’t start or runs at all, the first thing to check is the oil level. Check the dipstick, which is usually attached to a small screw cap that is similar to the gas tank cap.

Then, clean the dipstick by wiping it with a cloth. Look for high and low marks. The oil level should be in between those marks. If you notice that the oil level is too low, the next step is to check the fuel level.

Checking the oil level is an easy and quick task. It’s easy to do while the engine is turned off and the mower is parked on a level surface. Locate the dipstick, which is usually labeled “oil” or “oil can” with a contrasting color.

The cap also acts as the oil filler. Check the oil level with the dipstick.

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The upper mark indicates that the level of the oil is full, and the lower mark shows that the oil is low. There may also be a hatched mark on the dipstick to indicate that it’s acceptable to do so.

If you see the mark on the dipstick that says “additional oil is needed”, make sure that the level is higher than that.

You may notice the exhaust valve spitting out gas continuously. This is a result of the exhaust valve being stuck open. If the exhaust valve is stuck open, apply WD40 to loosen the stem. If you feel pressure, the intake valve is partially open or closed.

When the intake valve is closed, the mixture is pushed out of the chamber during the compression stroke. The carburetor should be cleaned and the engine rebuilt if the mixture is too high.

6. No spark

If your mountfield mower does not produce a spark, there are a few different things you can do. To start the mower, you will need to make sure that the control wire is connected correctly to the flywheel brake assembly and the engine coil.

When this is not done, the engine will not produce a spark, and this is a common cause of no-spark problems.

To test if the control wire is loose, you will need to remove the cowl on top of the engine and remove the flywheel if necessary.

If the problem is fuel-related, try cleaning the carburetor. If there is water or dirt in the float bowl, it can block the spark.

Another cause of a no-spark condition is the ignition coil failing. If the ignition coil is failing, you will need to replace it.

Once you’ve removed the spark plug, you can replace it. But you may not have noticed any improvements in performance.

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To check the ignition coil, you will need an in-line spark tester. Insert this tester into the spark plug boot and test for spark. If the tester shows no spark, then the ignition coil is likely to be the problem.

If this does not work, then you should consider another possible cause. If the ignition coil is faulty, the mower will be difficult to start.

A good place to start your mower is the garage. Alternatively, you can try a portable spark tester.

7. Clogged needle valve

If you’ve noticed a slow idle on your Mountfield mower, it may be the needle valve. The needle is located near the carburetor.

Remove the carburetor bowl and check the needle. It should be free of debris. If it’s not, it’s probably clogged. Look underneath the carburetor for a spring that holds the needle valve to the float hinge.

If it’s loose, turn the jet clockwise a quarter turn. Be careful not to over tighten the jet; it could damage the soft tip. The opposite is also true.

First, check the float. On some engines, the float may be clogged, allowing fuel to trickle out.

Another possibility is that the engine is upside-down, causing the fuel to leak out. If this happens, the float may no longer operate properly and a fire could break out.

The problem may also be a broken cable between the float and the engine. Once you find the problem, repair it as soon as possible.


In this comprehensive guide, we explore common issues faced by Mountfield lawnmower owners and provide practical solutions. From engine starting problems to cutting issues, we address troubleshooting steps to keep your lawnmower in top condition. Whether it’s maintenance tips or identifying underlying mechanical issues, our expert advice ensures your lawn care routine stays efficient and stress-free. Discover how to overcome challenges and enjoy a well-maintained lawn with ease.

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Mountfield Lawn mower Problems: Conclusion

If the needle is sticking or sluggish, try to disengage the linkage between the throttle body and air injector.

If you can, increase the idle speed slowly. After that, spray a solution of lubricant on the needle valve.

Once the valve is clean, restart the mower a few times. If the problem persists, visit a store to have the issue fixed.

You can also contact a manufacturer of Mountfield mowers to ask them for help.


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