Replace Petrol Lawnmower Governor Springs – Repairing Lawnmowers For Profit

How To Adjust Briggs And Stratton Governor Springs

In this article, I’m going to show you how to adjust and replace the governor springs on a Briggs And Stratton Petrol Lawnmower.

I’m guessing you’re here because your lawnmower is revving up and down and you want to stop it doing this!

“Don’t worry I’ll show you how to adjust and replace the governor springs first but there are lots of reasons why you probably won’t need to”.

How To Adjust The Governor Springs On A Briggs And Stratton Petrol Lawnmower

So, how do you replace the governor springs on a Briggs and Stratton petrol lawnmower? To replace the governor springs on a Briggs and Stratton petrol lawnmower you will need to simply unhook both springs from the governor flap linkage and unhook them from the opposite end near the carburettor. Use a small flathead screwdriver if necessary. There are no settings that will stop the springs moving erratically, however, to make the lawnmower run faster you can shorten the throttle spring.

Why Adjust Lawnmower Governor Springs?

There are two reasons you may want to adjust your governor springs, firstly to alter the speed of the engine, however, more commonly it’s because the lawnmower has started revving up and down and you have noticed the springs moving erratically.

Altering or attempting to stop the springs moving freely will not help the lawnmower if it’s revving up and down. This is a fuel

starvation problem and usually, the problem is caused by the carburettor needing to be serviced.

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I have seen hundreds of lawnmowers where the governor springs have been tampered with in an attempt to solve the problem. It doesn’t work.

If your lawnmower is struggling to idle or revving up and down and pumping out smoke, I would suggest leaving the governor springs alone as they won’t resolve the problem. The problem is that the carburettor needs servicing and more than likely a new diaphragm and gasket.

Here’s a video of how to replace the diaphragm and gasket. I strongly suggest doing this repair before tampering with the governor springs. It solves 90% of all running issues!

You can find all the parts for these repairs including diaphragm and gaskets and governor springs in my online parts store here.

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Can I Stop The Governor Springs From Moving?

The governor springs are designed to move freely and help the governor maintain the correct speed no matter the terrain or thickness of the grass. Stopping them from moving is more likely to cause further problems rather than fixing the problem.

How Does A Lawnmower Engine Governor Work?

Think of the governor flap and governor springs as an autopilot system for your lawnmower. They work in conjunction to maintain an even speed no matter what the conditions. For example, when cutting long grass or cutting on a hillside the governor assembly helps keep the engine at an even speed throughout.

Briggs And Stratton Governor Problems

Most problems occur when the carburettor and petrol tank has been removed from the lawnmower for servicing and not been put back together properly.

Usually, the linkage from the governor flap has not gone through the hole properly, this in turn stops the springs moving freely and often you will find that lawnmowers will run at full speed!

A great tip on the Briggs And Stratton 35 Classic Engine, for example, is to look at the plastic triangular part next to the carburettor, this is where the linkage connects the governor flap to the governor springs.

Make sure the linkage is through the hole properly and move the plastic triangular part, it should move freely in a tug of war type way with the governor springs.

Sometimes this little part gets pushed too far over and gets stuck on the other side of the stop.

Take a look at this tutorial video from my Youtube channel on how to replace the springs.

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Briggs And Stratton Governor Spring Adjustment

You can adjust the length or tension of the governor throttle spring to make the engine run slightly faster or slightly slower. The throttle spring is usually the longer of the two.

You can either shorten the spring by cutting some off the end or slightly bend the tang that it connects to.

Shortening the spring, or stretching further will increase the engine speed. To slow down the engine slightly bend the tab to make the spring have less tension.

Briggs And Stratton Governor Linkage Diagram

Here is a picture of exactly where the governor springs attach on a Briggs And Stratton 35 Classic Petrol Lawnmower.

How Do You Adjust The Idle Speed On A Briggs And Stratton Lawnmower

If your lawnmower uses a carburettor with a primer bulb the idle speed is set by the governor springs as mentioned previously you can shorten or lengthen the springs to increase or decrease the speed.

Usually, the Briggs and Stratton lawnmowers I work on that have a throttle use a bowl-style carburettor set up. You can alter the idle speed by locating the throttle cable and moving it back and forwards slightly, There may also be a screw adjuster on the carburettor.

Open and close the throttle without the lawnmower running and take a look at how the linkages move near the carburettor. You will see a part that opens and closes next to a screw adjustment. You can alter the idle speed from there.

Briggs And Stratton Governor Spring Installation

To install new governor springs on your lawnmower hook both springs to the little linkage that is connected to the governor flap.

Just slide the springs on by opening the hoop up with your fingernail a little bit, then attach the longer spring to the furthest part on the speed control, you will see a little hole there.

Now attach the small spring to the little tab that sits on the opposite side of the primer bulb. There are no further adjustments you need to make.

Help I Don’t Have Any Governor Springs

Not all petrol lawnmowers use the same governor spring set up however, you can usually work out which the governor springs are as they are connected to the carburettor.

Some lawnmowers don’t have a governor flap as the Briggs And Stratton 35 Classic does, instead they use a governor arm. The governor arm set up uses gears and flywheels inside the crankcase, however, even though you won’t see a governor flap, you will still see the governor springs that are attached to the throttle.

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I have not encountered a lawnmower where the internal governor has failed, so if you are having difficulty with your lawnmower maintaining an even speed or stalling I would strongly advise you to service the carburettor and make sure all the springs are connected and moving freely.

I have often seen instances where a throttle cable or a brake release cable is incorrectly fitted and therefore, hampering the governor mechanism!

Briggs And Stratton RPM Chart

Here is a useful resource on exactly what speed your lawnmower should be running depending on which type you have. Take note, there isn’t a massive difference between the speeds and as a rough and ready guide, I would suggest listening to the tone of the engine and using common sense.

https://www4.briggsandstratton.com/miscpdfs/RNT/Engine%20Specifications%20Chart_ms3992.pdf

What is The Correct Part Number Of Briggs And Stratton Governor Springs?

There are many various part numbers for Briggs and Stratton models and they do seem to keep updating the part numbers which is quite frustrating.

To find the correct part number for your lawnmower, take a look for a service ticket. It is usually located somewhere on the lawnmower deck and usually, it’s a silver rectangular-shaped ticket. Quote the make and model numbers to your local dealer or online to obtain the correct set of springs for your lawnmower.

The photographs in this article are of a Briggs And Stratton 35 Classic engine which is the most popular model to date.

Check out this page to find the correct governor springs for a Briggs And Stratton classic style engine. https://repairlawnmowersforprofit.com/recommended-products/lawnmower-springs/

What To Look For When Buying A New Petrol Lawnmower

If you are looking for a new lawnmower and planning to do any service work yourself I would suggest getting a branded lawnmower such as Briggs And Stratton, Honda, Hayter, Mountfield etc.

This way if you need any parts they will be available for you. Be aware of cheaper petrol lawnmowers with cheap Chinese copy engines on. You won’t find parts for these anywhere and they are a real hassle to work on.

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Help I Can’t Find My Governor Springs

If you are struggling to locate your governor springs then you probably can’t see them because the air filter box is in the way.

On a Briggs And Stratton Classic engine just remove the long flat-headed screw on top of the air filter box and remove the air filter. From here you will have access to everything you need.

Note. The Briggs And Stratton 35 Classic Engine is the perfect choice for anyone looking to repair lawnmowers for profit.

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To have full access to the governor springs with an air filter box on the side, just remove the air filter and undo the two bolts from the air filter box and set it aside. Be careful to keep hold of the carburettor so it doesn’t dropdown.

Refit the two bolts without the air filter box and you will be able to see all the governor springs.

You can see how all the linkages move by operating the throttle.

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Note. It’s always a great idea to take some photographs of any linkages or springs before removing them!

I hope this article helps you understand when, if and how to replace the governor springs on your petrol lawnmower.

Happy Mowing!