How To Stop A Lawn Mower From Smoking

A gas-powered lawn mower can spring unwanted surprises at the worst time!

But then again, it’s almost impossible to find a machine that won’t present an issue in its lifetime. And having operated a couple of gas-powered mowers, I know that a smoke-emitting model can get you thinking of possible accidents.

So, when my neighbor asked me to help fix her smoke-emitting mower, I wasted no time getting on the job. At the same time, I thought it’d be a good idea to document it for my readers.

Hi! I’m Stacy, and today, I bring a comprehensive guide on how to stop a lawn mower from smoking. Let’s start, then!

How To Stop A Lawn Mower From Smoking?

There may be different reasons behind a “smoking” lawn mower, but the problem is that most of these reasons are not identifiable from the outside. However, not all the issues will require you to hire a professional straightaway.

Interestingly, the best way to detect the fault in the mower that’s causing the smoke in the first place is by observing the color of the smoke. So, in the following sections, I’ll walk you through the different smoke colors, the related problems, and their quick fixes.

1. Black

A cloud of black smoke coming from your lawn mower signifies one of the most common problems, i.e., a malfunctioning carburetor and fuel system. As you may already know, these two systems regulate the mixture of gasoline and air in the mower. 

However, if the carburetor isn’t receiving enough air, the gasoline content in the fuel mixture will naturally become high. The engine will then burn the “gasoline-rich” fuel, thereby emitting black smoke. Other than that, the imbalanced ratio of gasoline to air can originate from a clogged or dirty filter, restricting the airflow. 

If you have noticed black exhaust from the mower, the first thing to do is check the onsite filter for accumulated dirt and debris. Almost all brands include instructions for cleaning the filter in their user manuals, so make sure to follow them. That said, the standard procedure is to remove, clean, and place it back. But if it’s too worn-out, I’d strongly recommend getting a new one. 

Once the filter is cleaned or replaced, initiate the engine and let it run for a few minutes to see if the problem has been fixed. If the mower is still emitting black smoke, then the issue may lie with the carburetor, which needs to be adjusted for increased airflow. 

Again, the user manual will carry the instructions for the purpose. However, if you’re a first-time lawn mower owner, it’s better to let a professional do the job.

2. White

White smoke is an indicator of yet another common issue, an oil spill in the engine, which usually happens while changing the engine oil. It can also occur when the oil is spilled on the housing during servicing or from an overfilled crankcase.

Generally, the mower emitting white smoke isn’t considered a big problem by users, as it should automatically go away after a while (when the engine is running). But if it doesn’t, there’s a good chance that the oil reservoir is overfilled, causing the engine to burn the extra oil. 

Apart from that, mowing on slopes greater than 15 degrees, mowing at the said angle, or tipping the mower altogether can cause the oil to spill on the engine. A simple solution is to run the engine on for about 15 minutes till the excess oil is burned off. 

However, if the problem persists for long, there may be a bigger issue at hand. For instance, worn-out seals of the combustion engine may allow oil leakage. Similarly, a leak in the crack cage or damaged cylinder and rings can also contribute to the problem.

Here, I should mention that a more severe problem pertaining to the emission of white smoke is the malfunction head gasket, which requires professional servicing. If your mower is still covered by warranty, you can easily get these issues fixed for little to no cost.

3. Blue

The reasons for your mower emitting blue smoke from the exhaust are pretty similar to that of the white smoke emission, viz., oil spill during mowing or refills. If you have to tilt the mower or mow on slopes, don’t forget to keep the spark plug tilted as well. 

Furthermore, both blue and white smoke may mean that you have used an engine oil different from what’s specified in the user’s manual. Long story short, there’s no scope for experimentation or preference here as you have to adhere strictly to the user manual!

Having used lawn mowers for quite some time, I found out that the best way to prevent the above-stated problems is by preventing overfilling the reservoir. And rest assured that this won’t require a herculean effort. All you have to do is use the dipstick on the reservoir to gauge the oil level. 

Start by unscrewing the dipstick cap and wiping the stick with a clean rag to get rid of the accumulated oil. Then, reinsert it into the oil reservoir and remove it once again. This is a foolproof way to compare the current oil level in the reservoir to that of the “fill” line inscribed on the stick. If the level is high, drain some of the oil following the steps in the instruction manual.

In case you need to add some oil back, do so in small amounts and keep an eye on the dipstick to determine the oil level in the reservoir. If you have a measuring cap in hand, fill the reservoir with 3/4th of the recommended amount and do the dipstick check.

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