So you started up your lawn mower, and it sounds like it’s over-revving. If your lawn mower RMP is too high, your mower will create an unusually high engine sound. There are a few common causes of this problem and luckily, they can usually be fixed quickly and easily. So, let’s dive in.
Why is My Lawn Mower Revving High? (The Short Answer)
High RMP stems back to the governor. A build-up of grass, bad springs, poor adjustment, and a damaged governor lever can all lead to high revving.
What is a Governor?
The governor controls the engine speed as loads are applied, such as when engaging blades or going up a hill. The governor will cause increased throttle by introducing additional fuel and airflow to the carburetor to maintain a steady RPM. The governor is controlled by the movement of the throttle, a set of springs, and link arms. So, how does the governor malfunction?
Common Causes of a Lawn Mower with RPM That’s Too High
Any time the governor is obstructed or damaged, the engine cannot adjust itself. A high RPM results from the governor’s inability to adjust the throttle. Let’s look to see what could cause this.
Debris on the Governor
You first want to check for a build-up of debris around the governor. In my experience, grass loves to collect in this area. As a result, you’ll need to get to the governor, which may require removing the air filter, fuel tank, or engine cover if the mechanism is hidden behind them.
With these removed, you should have easy access and be able to see any build-up of grass and junk. Next, you can check to see how the governor is working by moving the throttle from fully closed to fully open. If the governor is blocked, then the mechanism will not move correctly.
Checking the Two Springs
Different lawn mowers use different setups, but they all achieve the same job. Your spring could have worn, or it could have been damaged by debris. If the governor opens the throttle but can’t close it, the RPM will stay high.
To check this, you can see if the springs are under tension. If the springs are slack, they will not recall the throttle and the governor. If you have access to the springs with the mower fully assembled, then it’s best to check with the lawn mower running. This will show you exactly how the springs react.
Adjustment of the Governor Lever
The governor lever connects to the throttle linkage and the governor shaft, and controls the air-fuel flow and engine speed. The lever is mounted to the governor shaft, usually using a small bolted clamp. If the lever is loose or damaged, it will be unable to provide the correct adjustment to the engine, causing your lawn mower to rev too high. Inspect the lever to see if it has moved on the shaft or if it looks damaged.
How to Fix a Lawn Mower That is Over Revving
Before starting any fix on the governor, you’ll need to know what over-revving is. Your ears are a good gauge to identify a problem, but they’re not reliable enough to accurately carry out a repair.
For example, if you make a repair to solve a high RPM, you could accidentally end up setting it too low. As a result, you’ll be causing more problems because the lawn mower won’t have enough power.
Typical lawn mower engines have a range of around 2700-3000 RPM. You can confirm this with your specific engine. However, since your lawn mower doesn’t have an RPM counter, you’ll need to have an alternative solution to gauge it.
Inductive Tachometer Gauge
This inexpensive gauge connects to the spark plug lead and provides an accurate reading of engine RPM. It removes any guesswork when making adjustments to the governor. I’ll explain when to use a tachometer gauge on the specific fixes below.
Gaining Access to the Governor
With any repair to the governor, you’ll need unobstructed access first. Next, check if an engine cover, air filter, or fuel tank is getting in your way. If they are, then they’ll have to be removed. A small socket wrench or screwdriver should work fine, depending on your situation. Once the obstruction is removed, you can set them aside and move on to the fixes.
Tools to Remove Obstructions
- Screwdriver
- Socket Wrench
Cleaning out the Governor
Removing debris from the governor isn’t tricky, but it’s best to be gentle and not cause a new problem. If you had to remove the air filter, the carburetor’s inside will be exposed, and you’ll need to prevent debris from getting in. Let’s cover this in more detail.
Steps to Cleaning Out a Governor
First, start by removing the debris with your hands. I suggest you wear gloves since you might find something like a mouse nest that appeared over winter.
Be careful with the mechanism; remove what you can, making sure what you’re pulling out isn’t wrapped around a spring. The springs are delicate, and you want to avoid damaging them.
When you have the bulk removed, you can move on to using an air compressor or leaf blower to get the remaining junk out. Just be extra mindful if you have an exposed carburetor. Placing your hand over the carburetor opening should keep any debris out. Finally, once it is all cleaned out, give the mechanism a good coat of spray lubricant, making sure it doesn’t get into any exposed engine parts.
With this done, you can go ahead and put the lawn mower back together and test the RPM. Connect the tachometer gauge as per the instruction and start your engine. With the engine set to FULL, check the reading. It should be reading in line with the engine recommendations.
Tools Required to Clean out the Governor
- Protective Gloves
- Air blower
- Spray Lubricant
- Tachometer Gauge
Repositioning the Springs
You’ll notice that the governor lever has several small holes where you can attach the springs at different intervals. These allow you to adjust the tension of the various springs. By repositioning the springs, you will adjust the governor lever’s movement and, consequently, the engine’s RPM. Let’s go over how to adjust the springs to reduce the engine RPM.
Reducing the RPMs Using the Spring Adjustment
Start by attaching your tachometer gauge to the lawn mower, and start your engine. Take note of the RPM with the engine on full throttle. Once you have this reading, you can go ahead and turn off the lawn mower.
Next, take your needle-nose pliers, move the spring to the next hole, and take a new reading by starting your engine. Continue this process until you can get the RPM into the desired range. If you cannot achieve the desired RPM, you will need to move on to replacing the springs and checking the lever.
Tools Required to Adjust the Springs
- Needle-Nose Pliers
- Tachometer Gauge
Replacing the Governor Springs
I strongly recommend using new springs if you have identified that the governor springs need to be replaced. Any little fixes you do with your old springs may or may not last. Let’s look at the steps you’ll need to follow to get your governor working as it should.
Steps to Replacing Springs
Start by taking a pair of needle-nose pliers and removing the springs. Make a mental note of which spring goes where and its orientation. You’ll want to get the new springs back on the same way the old ones came off. They may get caught up if they go on backward.
Next, take your new springs and hook them into position using your needle-nose pliers. It’s that simple. With this done, give the governor area a good clean and spray it with a coat of lubricant.
Finish the fix by putting the lawn mower back together and testing the RPM. Take your tachometer gauge and check the RPM the same way you did after the cleaning process above. With the new springs properly in place, you should no longer have a lawn mower over-revving.
Tools & Parts to Replace Springs
- Needle-Nose Pliers
- Spray Lubricant
- Tachometer Gauge
- New Springs
Governor Lever Adjustment
The governor lever adjustment is the final fix to try if your lawn mower’s RPM is too high. Now, this isn’t adjusting the lever plus or minus. It’s simply adjusting the lever to be in the correct position. The governor shaft is usually square or half-round; this means the governor lever can only fit in one position. So, if yours isn’t in the correct position on the shaft, you’ll need to carry out a fix.
Positioning the Governor Lever Correctly
Start by using your needle-nose pliers to remove the attached springs and throttle arm. This will keep them out of the way, so they are not damaged. Then, use your wrench to loosen off the nut and bolt on the lever.
Once loosened, you can remove the lever from the lawn mower and inspect it for any damage. If you find that some damage looks beyond repair, I recommend using a new part. If you find the lever is bent, you’ll probably be able to straighten it by hand since it is made of thin metal.
Take either your new or repaired governor lever and place it back onto the governor shaft, ensuring it’s lined up correctly. Continue by fastening the lever’s nut and bolt and reattaching the springs and throttle arm.
To finish, clean and lubricate the area and reinstall the obstructed parts you removed from the lawn mower. Finally, take your tachometer gauge and check the RPM, as explained earlier.
Riding Mower Revs Too High: Causes + Solutions Specific to Ride-Ons
You may be asking, what about a riding mower that revs too high? Well, the fixes are just the same. The only real differences are that the engine is usually covered, such as with a tractor hood, and the size of the engine is larger in terms of horsepower. When it comes to governors, they tend to all work the same and follow the same principles. So, the next time you hear your lawn mower revving high, you’ll have four very quick and easy fixes for it.
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