How to start a lawn mower

How Do You Start A Lawn Mower?

Starting a mower is a straight forward procedure. But before you start your mower, it's always a good idea to check the fuel and oil level. 

 

Do a quick check over, looking for any loose or damaged parts. Turn the mower over, carburetor side up, and check for grass build up and blade condition.

 

 

 

 

How do you start a lawn mower? To start a lawn mower successfully you need to:

  1. Check oil level
  2. Check gas level
  3. Gas tap on (if fitted)
  4. Choke on (if fitted)
  5. Bail lever on
  6. Pull cord sharply

Oil Check

Oil is best checked on a cold engine, I check the oil level every time I fill the gas tank. Most mowers will be happy with 10w30 car engine oil and from empty, take about .65 of a quart (.6lt).

 

Why not go ahead and give your mower a tune-up, a lawn mower should be serviced at least once a year. The beginning of the new season is the best time to tune-up your mower.

 

This guide will help you service your mower in under an hour - " Lawn mower tune-up".

 

 

Fuel Check

If this is the first start of the season, consider the fuel quality. Gas that's been in the mower since last year is probably bad. So if your mower is hard to start or won't start - try draining the gas tank and filling with fresh gas. If the problem persists then a carburetor clean will fix the gremlins.

 

This easy to follow guide will walk you through the whole process - "Carburetor cleaning".

 

 

Fuel Stabilizer

Last seasons gas is the number one reason for lawnmower no starts. We all do it - put the mower away, not knowing for sure if that was the last cut. Before you know it, it's spring and guess what? The mower won't start, now you'll need to clean out the fuel system.

 

To prevent this happening next spring - at the end of this season, buy some fuel stabiliser, mixed with the gas, it'll keep it fresh for up to 2 years, so next spring it's pull and mow.

 

I use Sta-bil gas treatment,1 ounce treats up to 2.5 gallons, it prevents gumming and cleans the fuel system. It can be used in all gas powered kit including 2 stroke engines. You can check the price of Sta-bil on Amazon. 

 

 

Check Oil


mower oil level

Best to check the oil before starting the engine.

A low oil level will often prevent the engine from starting.

Add Oil


mower oil

Add small amounts and then check.

Too much oil is almost as bad as too little.

Check Oil

Best to check the oil before starting the engine.

A low oil level will often prevent the engine from starting.


mower check oil
mower add oil

Add Oil

Add small amounts and then check.

Too much oil is almost as bad as too little.

What Is A Choke?

The Function of a choke or priming bulb is to enrich the fuel mixture, so a cold engine starts smoothly. Gas engines run best when the ratio of air to fuel is 14.7 to 1. Meaning 14.7 parts air to 1 part fuel, also known as air fuel ratio (AFR).

 

Using the choke or priming bulb enriches the fuel mixture which counteracts the lean condition caused by the dense cold air. Engine manufactures commonly use two system types to achieve smooth cold starts.

 

 

Choke Plate

The Choke Plate type, usually controlled by a lever. Some of the latest choke plates are thermostatically operated meaning they are an automatic system. This choke plate reduces the amount of air and increases the amount of fuel supplied to the engine.

 

 

Primer Bulb

  • The second type is the Primer Bulb. This is very simple and easy to use, it creates a fuel rich condition by squirting extra fuel into the engine. You do this by pressing a rubber primer bulb, mounted at the carburetor.
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Choke


mower choke

Choke set to full to start a cold engine, after the engine warms up move the choke to the fast setting.

Some mowers use a snow flake symbol for choke.

Primer


mower primer

If your mower doesn't have a choke lever, then it may have a priming bulb.

If so pressing 3 times primes the engine with enough gas to start.

Choke

Choke set to full to start a cold engine, after the engine warms up move the choke to the fast setting.

Some mowers use a snow flake symbol for choke.


mower choke
mower primer bulb

Primer

If your mower doesn't have a choke lever, then it may have a priming bulb.

If so pressing 3 times primes the engine with enough gas to start.

Simple Starting Procedure

First pick a suitable location to start your mower, you don't want tall grass catching the blade as your trying to pull start the mower. If you have a throttle lever type system go ahead and move the lever to full choke. If you have the primer bulb type, press three times.

 

 

Choke 

If you have a throttle lever type system go ahead and move the lever to full choke. If you have the primer bulb type, press three times.

 

Bail Lever

Now hold the Bail lever also known as the dead man's lever, this is the bar at the top of the handle bars usually marked with a stop symbol. The Bail lever is a safety feature which modern mowers must have. Its function is to stop the blade from spinning and kill the engine within 3 seconds of bail lever activation.

 

Pull Cord

Now grab the pull cord handle and give it a good yank, the engine must turn over at 350 rpm minimum in order to produce a spark strong enough to ignite the fuel. If you find the pull cord very stiff to pull, make sure the blade isn't obstructed by dry grass on the deck, and check that the bail lever is working properly. 

 

 

Try Again

Most mowers don't run with the first pull so don't be disappointed. It may take two or three pulls. If it takes more than three pulls you may flood the engine with too much fuel. If this happens, just leave it sit for thirty minutes and try again, but this time don't apply choke.

 

 

After Starting

As soon as your engine has warmed up, move the throttle lever to fast/run (If manual choke fitted). A warm engine ran continually on choke will give off black smoke, run poorly and will shorten its life.

 

 

 

mower gas tap

Gas On

Gas valves are not fitted to all mowers. They are used to stop the flow of gas to the carburetor.

Gas tap should be turned off when the mower is in storage.

Choke On

If your mower has a manual choke lever move it to full choke.

If you have Auto choke, you can go straight to yanking on the pull cord.


mower choke lever
Mower primer

Press x3

Your mower may have a primer instead of a choke lever.

If so press it 3 times.

Gas On


mower gas tap

Gas valves are not fitted to all mowers. They are used to stop the flow of gas to the carburetor.

Gas tap should be turned off when the mower is in storage. 

Choke


Mower choke on

If your mower has a manual choke lever move it to full choke.

If you have Auto choke, you can go straight to yanking on the pull cord.

Primer


Mower primer

Your mower may have a primer instead of a choke lever.

If so press it 3 times.

Bail Lever

Most mowers will have a bail lever, also known as the dead mans lever.

This will need to be held while you yank the cord.


mower bail lever
starting mower

Yank

Most mower won't go on the first pull, but if it takes more that 3 pulls, it's likely the mower is flooded.

Let it sit awhile and try again.

Run

When your mower starts, move the throttle lever (if fitted) to fast/run position.

Running the mower on choke will cause black smoke and sluggish performance.


mower throttle lever

Bail Lever


mower bail lever

Most mowers will have a bail lever, also known as the dead mans lever.

This will need to be held while you yank the cord.

Yank


Starting a mower

Most mower won't go on the first pull, but if it takes more that 3 pulls, it's likely the mower is flooded.

Let it sit awhile and try again.

Run


mower throttle lever

When your mower starts, move the throttle lever (if fitted) to fast/run position.

Running the mower on choke will cause black smoke and sluggish performance.

Related Questions

How can I start my pull start lawnmower if I'm not strong enough to use the starter cord? You can adjust valve lash, this will reduce the amount strength needed to turn over and start the mower engine.

 

 

 

How to start a lawn mower in one pull? Make sure your gas is fresh, prime the engine, put the bail lever on and now one good pull.

 

 

 

Auto Technician and Writer at | Website

John Cunningham is an Automotive Technician and writer on Lawnmowerfixed.com. I've been a mechanic for over twenty years, I use my knowledge and experience to write "How to" articles that help fellow gear-heads with all aspects of mechanical repairs, from lawn mowers to classic cars.