Lawnmower Runs Too Fast-Help And Repair

Help!  My Lawnmower Runs Too Fast

Do you have a lawnmower that runs too fast? perhaps for some reason it’s running absolutely flat out and you don’t know why?

Let Me Show You What The Problem Is.

I have seen this happen many times before and luckily it’s not usually too difficult to resolve the issue. In fact, in this article, I will tell you why it happens and show you how to fix a lawnmower that runs too fast.

What Causes A Lawnmower To Run Too Fast?

So, what is the most obvious cause of a lawnmower that runs too fast?  The most obvious answer is the governor flap assembly is stuck open.

The governor flap is a long semicircle shaped piece of plastic that runs around the outside of the flywheel. This is a common set up on most lawnmowers but not all! (I’ll cover other setups shortly)

You will find this set up on a Briggs And Stratton 35 classic engine for example. The reason a lawnmower runs to fast is because the governor flap isn’t moving freely so we need to identify why.

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First Remove The Spark Plug.

Take off the recoil cover on your petrol lawnmower and you will have access to everything you need. Now you can see the governor flap. Try moving it around, it should be attached via a small hole on the end to a linkage.

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When you pull it away from the flywheel it should bounce back to the original position against the springs. The governor flap sets the speed of your lawnmower. It does this by moving away from the flywheel when the lawnmowers is running. The governor flap is attached to a small linkage and two governor springs that go to the carburettor set up.

The further away the governor flap is from the flywheel the faster the lawnmower will run.

  • Note The governor flap automatically adjusts when the lawnmower is running there is no need to adjust anything!

Most times I see a lawnmower that runs too fast it’s because everything is jammed up with grass around the springs or something has attempted to build a nest in there. On occasion, the governor flap has even snapped where it connects to the linkage.

Check all the surrounding areas and make sure everything moves freely.

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Other Reasons Your Lawnmower Runs Too fast.

Some other reasons the governor flap gets stuck open are when someone has dismantled the lawnmower and removed the starter recoil they haven’t re-assembled it properly. Sometimes when refitting the cover they use screws that are too long and this can obstruct the governor flap.

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Make sure the linkage that connects through the small hole is completely through the hole, often if someone has taken the carburettor and petrol tank off the lawnmower they will incorrectly refit this linkage. Make sure all the governor springs move freely and the linkage is sitting correctly.

You can alter the speed of a lawnmower slightly by bending the metal tab where the long governor springs connect to. To make it run faster bend the tab so the spring stretches slightly further. To slow the engine speed bend the tab to make the spring have less tension.

  • Note. This will NOT help if you have a lawnmower that’s hunting surging, revving up and down or pumping out white smoke.

If your lawnmower does those things leave the springs alone and check out this article:

What If My Lawnmower Doesn’t Have A Governor Flap?

Don’t worry. All is not lost! There are a few simple things we can check on a lawnmower that has a governor arm and not a governor flap.

Firstly remove the air filter and you will see a gold part that looks like a small coin or a gold butterfly. This is the choke.

Visually inspect the choke opens and closes properly by moving the accelerator control on your lawnmower. Put it onto choke and see if it closes fully then open it up to full throttle and see if the part opens fully. You do not have to start the lawnmower engine to do this.

If you have a lawnmower that starts and has an adjustable speed control that doesn’t work it will be because the valve is stuck open. With this fault, you will struggle to start the mower from cold as it isn’t actually choking correctly. It just depends which position it’s stuck at as to how it will run.

Check The Governor Arm

The governor arm is usually towards the back of the lawnmower, it will have metal linkages and springs that connect from the arm to the carburettor. Make sure the arm moves and springs back and forth freely and there are no obstructions.

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Open up the throttle and notice which parts move. There is a screw on the top of the carburettor where a little lever opens and closes against. Make sure it moves freely and springs back.

Check The Throttle Cables

The throttle cable often runs underneath the carburettor and they can be adjusted by loosening the screw and sliding the position of the cable. Over time the cables stretch and you may lose some power. If the adjusting screw has come loose however the cable could be either obstructing the governor arm or holding the throttle permanently open.

Have You Serviced The Carburettor?

If you have just serviced the carburettor it’s possible that you have not put it back together correctly and the lawnmower is getting the incorrect supply of fuel, although it’s unlikely to run at all, sometimes you just need to retrace your steps.

  • For example, if you have a lawnmower that was running at the correct speed before you started doing other repairs it’s possible that this is the cause and somethings not gone back together correctly.

Check The Ignition Coil!

Just recently I repaired a lawnmower for profit and it ran absolutely flat out. I honestly thought it was going to explode! After taking a look around it, I noticed the ignition coil was right up against the flywheel and even scoring it.

The ignition coil had splayed out and bent and was just generally a real mess, actually having seen it I couldn’t believe it ran at all. I replaced the ignition coil and set the gap using an old greetings card for the gap thickness and fired up the lawn mower.

The problem was solved and the lawnmower ran perfectly. I was given the lawnmower free of charge as it was in poor condition I repaired it and made £50 profit by selling it on facebook marketplace.

Ride On Lawnmowers That Rev Too High

On very rare occasions the governor inside the crankcase becomes faulty and unfortunately, it’s a very expensive repair, If you have tried everything else and it looks fine then it may be worth opening up the crankcase and taking a look. This would be my last resort but if you have spent a lot of money on a ride on lawnmower the last thing you want is a broken internal governor part falling off into the rest of the rotating parts in the crankcase.

What To Look For When Buying A New Lawnmower

I just want to give a few pointers on how to choose a new petrol lawnmower and types to avoid buying and having the same problem again.

There is a good reason branded lawn mowers cost more than cheap unbranded ones you can pick up at supermarkets.

The reason is you can always get spare parts for lawnmowers such as Honda Briggs and Stratton Hayter etc.

Imagine saving a few pounds buying a slightly cheaper lawnmower only to find something as cheap as the governor flap needs replacing and you can’t get a replacement part anywhere?

If the governor flap didn’t work for any reason and the cheap lawnmower only ran at full speed you would most likely be scrapping it because you can’t buy a part for it that should be incredibly cheap!

That’s incredibly frustrating, So buying an unbranded petrol lawnmower in the first place will more than likely come back to bite you!

Find my current recommendations here

How To Find The Correct Replacement Part For Your Lawnmower.

If you take a look at your lawnmower deck it should have a service ticket on with all the information on. It’s usually a silver rectangular shaped ticket. You probably won’t find one of these on an unbranded lawnmower!!

You can use the information on the ticket to quote to your local lawnmower repair dealer or when trying to find a part online. Take a look at the Recommended Products Section of this website as we should be able to point you to whatever you need.

You can find it here

So hopefully this article has solved your problem whether your own lawnmower is running too fast or you have picked one up to repair for profit.  

Be sure to leave a comment in the comments section on my Youtube channel if this article has helped you. 

If you have a lawnmower that won’t start you may wish to take a look at this article

You can find lots more information and start repairing lawnmowers for profit by checking out my online training here

Happy Mowing



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