How to Change Your Lawnmower Blade and Otherwise Tune That Baby Up

The Mower the Merrier

Easy tune-ups for your lawnmower

It’s shocking how many times an otherwise intelligent human can cut a hose in half with a lawnmower while thinking the blade would clear it by several inches.

Please allow that oblique admission of idiocy to preface today’s topic: getting in touch with your lawnmower.

For many of us, the manual that came with the lawnmower is a manifesto of guilt.

For example, my manual says to clean the engine regularly with a soft cloth or brush, clean the underside of the mower after each use, and replace the spark plug annually.  Three things I’ve never done in 4 years. 

The manual also says to inspect the blade after striking a foreign (or domestic) object, such as a hose, toy, rock or stick. 

I’ve never inspected that blade once.  Till today.

To say that the blade didn’t look great would be like saying charred-to-a-crisp asparagus looks ‘a little wilted’. 

I put it off for years and then discovered that a blade-change takes 5 minutes.  A new blade makes cutting the lawn way nicer - the mower runs more efficiently, the grass tips aren’t brown and jagged, and the lawn looks smooth instead of tufty as a sheep.

Blade of Honour

Here’s how to change your blade fast and sassily:

Tip from reader @fosterrob - remove the spark plug cap before starting work just to ensure that the engine doesn't accidentally start.

1. Tip the machine up on edge. To avoid soaking your air filter with oil (yes, I did) make sure that the air filter is on the high side.  You may have to remove the screws that hold the side-discharge chute in place so you can tip the mower up easily.

2. TIP: Never turn your lawnmower ‘turtle’ to work on the blade while the machine is upside down.  It will pee oil into your air filter and all over your driveway. I’m just here to help.

3. Loosen the hex-bolt at the center of the old blade.  Block the blade with a chunk of wood so it doesn’t spin while you apply pressure.

(A chunk of scrap wood blocks the blade from spinning)

4. After loosening, remove the bolt and the old blade. 

(Your old blade might be significantly used like mine - the metal is actually torn and you can see the driveway through the blade - this is a horrible example of neglect and would make a nasty shard if it split off while the mower was running)

5. Install the new blade, making sure the side stamped with ‘bottom’ (or sometimes just a part number) is facing away from the mower.

6. Re-tighten the assembly. 

To Air is Human
Next, remove the old air filter.  Drive to Canadian Tire, taking the old filter with you so you get an exact match.  (Guessing the dimensions doesn’t work.  If you had that degree of spatial awareness you’d still have one hose instead of two).

If the old air filter is soaked with oil for reasons you shouldn’t admit to knowing, put it in a plastic bag.  Place the first bag in a paper bag so no one at Canadian Tire knows your shame.

(Above: What happens when you turn your mower 'turtle' to work on it)

When you get home, load the new air filter into position.  You’re almost done with your tune-up.

Oil is Not Lost

Your final step is changing the oil. Do it when the mower is warmish because warm oil flows better.  Locate the oil cap.  It usually says ‘OIL’ on it, with a nod to those of us who only go there once every 4 years.

Get a helper to hold a suitable container (something sealable that you can take to your local Hazardous Waste Day or store on the shelf in your garage for years while you keep forgetting to go to Hazardous Waste Day).  Tip up the machine and let the oil flow into the container. 

TIPPING TIP: Gas tends to egress from the fuel tank when tippage is applied, so put plastic wrap over the fuel opening and then screw the top down over the wrap before tipping.

When the oil tank is empty, drop the machine to a level surface again.  Use a funnel to pour the recommended oil (10W30 works fine) into the oil chamber. 


The manual cunningly says “Do not overfill” while not specifying how much it takes to fill it.  It will be tempting to guess as the oil glugs into the funnel.  But really, how well has this guessing thing gone so far?  So keep removing the funnel and inserting the dipstick to check the level. Stop when you reach the upper limit mark. 

That’s enough fun for today.  Check your own manual for other tips including “To reduce the possibility of explosions, keep cigarettes away from all fuel-related parts.”

Comments

[Michael]

You forgot the part where you bend the governor spring plate to kick up the horse power. With a little extra juice, you don't have to worry about foreign objects.

[Abi]

mag<
I never use the manual either to check it..i;ve used something else to clean the gunk underneath that anyapper doo. man i must be doin something wrong!!

[Michael]

I fear for the two of you's cars.

[Mag]

Ah, the governor. I've never touched that sucker since a bad go-cart experience.

Never fear for my car though. After driving my very first car (a Honda CRX) for 4 years without changing the oil, the reaming out I got from the dealership was enough to change my evil ways.

[Abi]

Mag,
that is so funny. my first car my mother gave it to me.. mazda. for a long time i didnt change the oil.. that it caused shaking problems for the car... think of what a nightmare that would've been if it had shut down or blown up in the middle of nowhere. talk about prohectic chaos!

[MTD Mower Parts]

Thanks for all of the steps with pictures, they really help. I haven't gotten around to changing my blades yet, but when I do I know I can count on this site. Thanks!

[Abi]

i give this article 5 stars

[allison]

Very good pictures-not really like
baking cakes and doing laundry but
we didn't think it was going to turn
out like this did we. Painted the outside
of the house last year even the chimney-move over cause yes I do it all! thanks