Petrol lawnmowers are fantastic. They’re powerful, durable, and supremely portable, which is ideal for medium to large gardens, or working away from mains power. But, the thing that makes them so valuable – the engine – can sometimes be their main disadvantage, as it can be difficult to start if you’re unfamiliar with petrol engines.
So, if you’re not sure how to start a petrol lawnmower, you’ve come to the right place. At Hughie Willett Machinery, we’ve pulled together a step by step guide to help you learn more about starting your petrol mower. Plus, we’ll explore some of the main reasons your mower may be stalling, or not working as it should.
Keep reading to find out more from the team…
Parts of a petrol lawnmower
First things first, you may find it helpful to understand what parts are interacting when you start a petrol lawnmower. In this section, we’ll take you through the different components of a petrol lawnmower engine, and how these contribute to the overall function of your machinery.
Note: in our example, we’ve used the Husqvarna LC140SP Petrol Lawnmower to highlight several aspects of a petrol lawnmower engine. The location or design may be subject to change depending on the manufacturer.
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Starter rope: when you pull a starter rope, it uncoils. This energy engages the clutch and causes the crankshaft to spin, which starts the engine. Once the engine is running, the clutch disengages.
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Fuel cap and tank: the fuel tank is fairly self-explanatory. This holds fuel (usually petrol), which flows into the engine and is burnt to create power.
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Oil cap and tank: oil helps to keep the engine lubricated, and is part of the cooling system. Attached to the oil cap is a dipstick to help you measure the right levels of oil for your machine.
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Air filter: the air filter is designed to capture any dirt or debris whilst allowing air to enter the engine. The air filter is encased to protect it from external damage.
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Exhaust: the exhaust allows gases produced by combustion to escape, and stop from building up inside the engine.
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Spark plug: as the name suggests, this provides the necessary spark to burn the fuel/oxygen mixture that powers the engine. This is covered to prevent accidental damage during use.
Whilst it can’t be seen, petrol engines also have an element called the carburettor. This is where fuel and air are mixed to create the conditions for combustion.
How to start a petrol lawnmower
Now that we’ve clarified the important parts of your mower engine, let’s take a look at how to start a petrol lawnmower from scratch.
Preliminary steps
Before starting the engine, there are several checks you should complete to ensure your petrol lawnmower is in safe working order, including:
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Syphon out any stale and stagnant fuel from the tank via the top, and by draining the carburettor. Petrol degrades over time and can become corrosive, which can damage your fuel tank and engine.
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Check the air filter is clear, and the spark plug is clean. These are essential components in a combustion engine, and will cause your engine to fail if they’re not properly secured or in good condition.
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Remove any blockages from the mower deck that could obstruct the blades during use.
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Check for any signs of damage or wear and tear that could cause issues. Replace or repair parts as necessary.
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Make sure all connections are securely tightened and attached. Loose joints could come apart during use, which is incredibly dangerous.
Petrol lawnmowers require more maintenance with each use than other mowers, which does take plenty of time and effort. But, considering a well-cared for lawnmower can stay in service for several years, we think this is a fair trade off.
Starting the engine
Once you’ve completed your preliminary checks, it’s time to actually start your petrol lawnmower.
Step one: Fill the fuel tank with petrol.
Top tip: try to only fill with as much petrol as you need. Fuel left in the tank can go stale, which is not only a waste of money, but can also affect the performance of your mower.
Step two: Prime the engine. This is done by pressing the primer button on your engine (usually three times, although check your manufacturers recommendations). Priming the engine allows air in to encourage the fuel to burn.
Step three: Disengage any safety levers. These are designed to stop accidentally starting the engine, so need to be released before you begin.
Step four: Pull the starter cord sharply until the engine starts.
Remember, these are general guidelines. Some petrol lawnmowers will have a throttle that needs to be pushed down before you can start the engine. Alternatively, some mowers may make use of a simplified starting mechanism to make the whole process easier. Always check the manufacturer's instructions if you’re unsure.
What petrol do lawnmowers need?
Choosing the right fuel for your engine is vital to ensure it works properly. Most petrol lawnmowers simply need unleaded petrol, and will have a separate compartment on the engine for oil.
However, this will change if you have a 2-stroke or 4-stroke engine. These need a combination of oil and petrol, which you can mix yourself or buy premade. Alternatively, commercial and ride-on mowers often take diesel, as they have more powerful engines.
Considering a battery mower instead? Explore our Push Lawnmower Buying Guide to find out more about the different kinds of mower available.
Why isn’t my petrol lawnmower starting?
Now you know how to start your petrol lawnmower, you should be well on your way to keeping your garden neat and tidy. But, what happens if it stops working in the middle of the job, or struggles to start in the first place?
There are many reasons your petrol lawnmower may be having issues with turning on, stalling, or stopping midway through a task. Below we’ve pulled together some of the most common issues, and how you can fix them.
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Your fuel tank is empty: this is the easiest to fix – simply follow step one of our guide and make sure the tank is filled before you start the engine.
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Your air filter is clogged and dirty: air filters are vital for combustion engines, as they need oxygen to burn the fuel. Make sure you clean out your air filter, and replace it if necessary.
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The spark plug is dirty or worn out: a malfunctioning or broken spark plug means your engine will not work. You’ll need to replace this immediately if there are any issues.
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Your oil is low or dirty: make sure you replace or top up your engine oil. Oil is a lubricant, and important within cooling systems to prevent your lawnmower from overheating.
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The fuel filter needs replacing: fuel filters prevent dirt and debris from reaching the carburettor and reducing performance. Usually, fuel filters need replacing at least once a year.
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The blades are obstructed: clumps of grass can get stuck and block the blades, and will need clearing by hand. Make sure to fully turn off the engine, and disconnect the spark plug, before putting your hand anywhere near the deck.
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The carburettor is blocked, dirty, or faulty: if your petrol lawnmower is sputtering unusually, or stalls a lot, the problem might be with the carburettor. You may be able to clear this with a carburettor cleaner, or it might be worth having the engine serviced.
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You need to adjust the cutting height: long grass can cause a lot of problems for petrol lawnmowers, particularly if the cutting height is at the wrong setting. Try adjusting this to see if that stops your mower from stalling.
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The starter rope is faulty, blocked, or broken: starter cords go through immense stress with each use of your petrol lawnmower, and can snap or fray enough to prevent them from working properly. If this happens, you’ll need to have the cord replaced.
Top tip: getting your petrol lawnmower serviced regularly can save you a lot of frustration. It can also help to save money as you can resolve any issues before they develop into problems.
Looking for your new petrol lawnmower?
Here at Hughie Willett Machinery, we have an excellent selection of lawnmowers from renowned industry leaders like Stihl, Husqvarna, Cobra, and Weibang. From larger professional models, to smaller domestic mowers, we have what you need right here.
Looking for more specialist advice? Our fantastic team of experts are on hand to help you throughout your buying journey. Give us a call on 0121 308 1262, or get in touch online today.
Buy lawnmowers from Hughie Willett Machinery today!
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