Buying the correct type of lawn mower is vital for maintaining your property. Not only are there many different types of lawn mowers available, but there are many different engines as well. You may be wondering, can my lawn mower engine run backwards?
Your lawn mower engine can run backwards, but it shouldn’t. If you’re experiencing this, it’s likely the flywheel key has been affected, which is a device that is designed to keep your lawn mower’s internal parts safe, so it’s crucial you check there first.
In this article, we’ll be going in depth about how your lawn mower engine has the ability to run backwards, the usual cause of this, and how you can fix this. If you’re interested in learning more about these topics, keep on reading.
Check the Flywheel Key for Damage
As we stated above, the usual cause of the engine beginning to run backward is the flywheel key. The flywheel key is actually a fairly frequent problem for most engines, so it’s best to check there first.
If you find yourself with an engine that’s running backwards, it’s likely the flywheel key has sheared off. This is usually the result of mowing over something large like a rock. You can find the flywheel key mounted on the end of the crankshaft, so once you locate it, you can begin inspecting it for damage.
When mowing your yard, the blade, the crankshaft, and the flywheel are spinning and working together to create movement. When you hit an immovable object, the crankshaft slows down, but the flywheel doesn’t stop as fast. This causes the flywheel key to become sheared and can result in a backwards running engine.
Your best bet, in this case, is to replace the flywheel key, as it is probably damaged beyond any further use at this point.
Replace the Flywheel Key
Depending on the make, model, and type of engine you’re working with, the type of flywheel you need to purchase may vary. Replacement flywheel keys are relatively cheap and available at any hardware store.
If you’re working with a Briggs & Stratton piece of machinery, you can easily replace your damaged flywheel key with this Briggs & Stratton Flywheel Key 1 pck. This product comes with a set of 3 flywheel keys and will keep your lawn mower running the way it should at peak performance.
No matter what brand lawn mower you’re working with, you can easily find the appropriate flywheel key replacement for you. It’s vital that you act fast, as a sheared flywheel key can cause other problems for your lawn mower besides a backwards running engine.
After you’ve purchased the correct flywheel key replacement for your lawn mower, it’s time to install it. Below, we’ll go step by step on how you can do this successfully.
Step One: Remove the Gas Tank
The first step to replacing your sheared flywheel key is by removing the gas tank. You should also remove the oil dipstick and clean it before putting it back on.
Once you’ve rinsed off your dipstick and removed the gas tank, ensuring oil won’t spill out, remove the red cooling shroud. Once you’ve taken off all the necessary equipment and put it to the side, it’s time to reach for your replacement flywheel key.
Step Two: Remove Damaged Flywheel Key
Now you’ll want to remove your sheared flywheel key and replace it with your new one. While it’s possible to remove your old flywheel key without a flywheel puller, it’s not recommended as it’s quite difficult.
If you’re in need of a flywheel key puller that will save you time and energy, this Briggs & Stratton 19203 Flywheel Puller (link to Amazon) will do the trick. Using this product will make changing out your flywheel key much easier, and it’s a smart investment in the long run.
Once you’ve removed your damaged flywheel key with your puller, remove the nut and pry the old flywheel off the crankshaft. Since your key has become sheared, it’s likely to leave residue or fall apart into pieces.
Once you’ve successfully removed the old flywheel and cleaned up any remaining pieces that may be lying around, it’s time to insert the new flywheel key into its desired location.
Step Three: Insert New Key
Once you’ve removed your damaged flywheel key, you can remove your new key from its packaging and insert it in its proper location.
Before you place your new key on the crankshaft, make sure to tie the dead man’s clutch lever against the mower to ensure it stays while you are mowing. Once you’ve done this, you’ll want to insert the key with the thicker end downward to make sure it’s properly installed.
If you’re more of a visual learner and you want to ensure that you’ve followed each of these steps correctly, watch the video below for a step by step on how to properly remove your damaged key and replace it with your new one.
Step Four: Tighten Everything
The last step you’ll need to take involves tightening all your gear and applying oil to the end of the crankshaft.
Once the flywheel has been successfully installed, you can place the nut, the washer, and the cup onto the crankshaft to secure your new flywheel. You can then begin tightening all your equipment to ensure it stays put.
Twist the flywheel a couple of times to make sure it’s not obstructed by anything, and it can turn with ease. If you are constantly going through flywheel keys, it’s likely the nut is not tight enough, so it’s vital that you twist it until it’s as tight as possible.
Once everything is secure, you can top the engine with new oil. Once you have successfully followed all these steps, your engine should be running normally and be good to go. While sheared flywheel keys are common, it’s an easy fix if you know what you’re doing and what tools you need.
How to Avoid a Backwards Running Engine
While this is actually a pretty common occurrence, there are easy ways to prevent your engine from running backwards in the future.
For starters, be mindful where you use your machine, as mowing over large and immovable objects will most likely cause issues for your engine. It’s also important to ensure that when you install your flywheel key that you tighten it as much as possible.
Loose flywheels won’t do you any good, as they’ll continuously become damaged and will cause you to have to constantly replace your equipment. In the video below, you can get an even more in-depth explanation of how you can prevent your flywheel key from becoming sheared.
Conclusion
So can your lawn mower engine run backwards?
While the answer is yes, your engine running backwards won’t be helpful to you, and is likely to be the cause of internal damage to the flywheel key. If your engine has begun to run backwards, it’s likely you’ve mowed over a large immovable object such as a rock.
You should begin by inspecting the area to see if your flywheel has become sheared. If this is the case, you should follow the steps we went over in this article to ensure you’ve removed and replaced your flywheel key successfully.
We also went over how you can prevent this from happening in the future, such as being mindful where you use your machine and making sure that your flywheel is tight enough on the crankshaft.
Now you have all the tools and information you need to fix your backwards running engine.