Why Your Craftsman Lawn Mower is Smoking: Solved!

You may have started your Craftsman lawn mower and noticed a big cloud of smoke or maybe your mower started smoking once the engine became hot.

All you can think of is, “How much is this going to cost?” Hopefully, you’re lucky enough to have a simple engine problem that can be fixed easily and is not a more costly repair.  

A Craftsman lawn mower may smoke because the engine’s air filter is plugged; there is an inefficient engine oil level; the engine may have a bad gasket, or there may be a valve train or piston ring problem. 

Keep reading and I’ll share with you the most common causes that will make your lawn mower smoke. 

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Follow all safety instructions provided in your equipment operator’s manual prior to diagnosing, repairing, or operating.Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

5 Reasons Your Craftsman Lawn Mower is Smoking 

I’m going to take you through the 5 reasons your Craftsman lawn mower could be smoking, starting with the simplest item to diagnose and moving on to the more difficult items. 

Plugged Air Filtration System in Your Craftsman

You should start by checking your air filter system. It is very easy to check. If this happens to be the reason your mower is smoking, then you lucked out and won’t have to move on to the tougher items to diagnose. A plugged air filter system will be one of the least expensive repairs. 

• Remove the air filter cover which is located above the carburetor so it can pull in clean air. You may have to remove the cover by turning a couple of knobs or a screw. Sometimes the cover is held on with a couple of clips. It can vary from engine to engine. 

• Pull the air filter out of the air filter housing. Sometimes you will find the air filter along the side of the engine and next to the carburetor. Take caution when working around the engine to prevent burn injury if the engine is hot. 
• When removing the filter, be careful not to let any dirt fall into the engine intake pipe. The point of using a filter is to keep dirt from being drawn into the engine. 
• Inspect the filter for clogging from dirt and grass. If your air filter is clogged, the engine will not be able to pull in the air it requires and won’t be able to breathe. When the engine is unable to draw air through the air filtration system, it begins to draw air from the engine crankcase or another internal part of the engine. 
• Replace a clogged air filter or simply knock any loose dirt out of the air filter if it doesn’t appear to be in bad condition. Hold your air filter up to the light and make sure you can see light through every part of the filter. If the light is blocked by a dirty filter, you must replace your air filter. 
• Replace the air filter cover. 

When air is being drawn from the internal components of the engine due to a lack of air through the air filter, it often pulls in oil from the crankcase. The engine burning off this oil can cause your lawn mower to smoke. 

You can find many common Craftsman air filters on Amazon. Make sure you have your engine information to make sure you are purchasing the correct filter for your lawn mower.   

Read about how often you should check your air filters and how to clean them in my guide on air filters.

Too Much Oil or Too Little Oil in Your Craftsman Mower 

Not having the correct oil level in your Craftsman mower may be the cause of your lawn mower’s smoking. Check the oil level in your mower to verify it is at Craftsman’s recommended level. 

Low Engine Oil Level 

If you find your engine oil level is lower than recommended, you can develop a problem where your engine is burning very hot due to the reduced oil lubrication.

Your engine can be running so hot it begins melting the internal engine components and burning oil causing smoke. 

You can try adding engine oil to see if the engine stops smoking, but most of the time at this point, it is too late for additional oil to work. 

Tip: Always check your engine oil level before each mowing to ensure your oil level is correct and you haven’t developed an oil leak. 

High Engine Oil Level 

Many lawn mower owners are not aware that having too much oil in their lawn mowers can be detrimental to engine performance. Too much engine oil in your lawn mower can cause excessive crankcase pressure.

This pressure causes oil to get into the cylinder and possibly into the air intake system through the valve train.  

When this happens, oil that gets into the cylinder begins to burn off when the engine gets hot. Your lawn mower begins to smoke from the burning oil. 

To fix this problem, you will need to remove the excess engine oil until you are at Craftsman’s recommended engine oil level. You can do this by draining a little oil or using a method to extract some oil.

An inexpensive turkey baster works well to remove oil. You can also remove some oil through the drain plug or engine oil filter if your model uses an oil filter. 

For more information on the results of filling your lawn mower with too much oil, read “This is What Happens If You Put Too Much Oil in a Lawn Mower”. 

Piston Ring Problem in Craftsman Mower 

This is where diagnosing and repairing gets a little more difficult as you begin to look at internal engine components.  At this stage, you may want to bring your lawn mower to a certified small engine mechanic if you are not mechanically inclined or keep reading to learn more. 

Check for oil on the spark plug by removing the spark plug. You will need either a ¾” or 5/8” socket to remove the plug.

Inspecting the spark plug isn’t necessarily going to tell you what type of engine problem you have but finding excessive oil buildup on the spark plug signifies a larger internal engine problem. 

A spark plug with oil buildup can be an indication of a ring problem and scoring to the cylinder wall. When scoring occurs in the cylinder, the engine can draw oil into the combustion chamber and begin burning it.

This will create smoke while your mower is in use. In this situation, you may have to replace the engine in your Craftsman lawn mower. 

Valve Train Problem in Craftsman Mower

The only way to determine whether you have a valve train problem is to remove the cylinder head and perform a leak-down test. This should be performed by a trained small engine mechanic.

When a valve gets burned by the engine overheating, the edges of the valve begin to fall apart. This is referred to as a burnt valve. 

Another indication you may have a burnt valve or timing problem is if your muffler begins to glow red hot. In this case, the valve needs to be replaced, and the seat must be ground.

The seat is where the valve contacts the engine block to complete the combustion chamber. The valve and seat must be cut at certain angles to make the valve seat correctly. 

Bad Engine Gasket in Your Craftsman 

A bad gasket on your engine can cause engine oil to leak into the muffler. This will cause the engine to smoke as the oil is burned off. It may seem simple to identify a failing gasket, but it can be more difficult than you think depending on the location of the bad gasket. 

White, Blue and Black Smoke from Your Craftsman Lawn Mower 

The color of smoke from your Craftsman lawn mower can sometimes lead you to the type of engine problem you have.

I find it best to go through the steps above to narrow down the problem, but here is a quick summary of the different colors of smoke and what can be causing white, blue, or black smoke. 

Craftsman Mower Blowing Black Smoke 

Black or gray color of the smoke is most likely due to the engine running too rich. This means more fuel is being burned than air. The first thing to check, in this instance, is the air filter.

Replace the air filter if it is clogged and unable to be cleaned. If this doesn’t seem to be the issue you will want to check for another air flow restriction. 

Craftsman Mower Blowing Blue or White Smoke 

Blue and white smoke coming from your Craftsman mower is usually due to your mower’s engine burning excess oil.

It is best to follow the guideline above to identify the root cause beginning with checking the engine oil level. Then continue to check for damage to the piston rings, valve train, or engine gasket. 

Complete Regular Craftsman Engine Oil Changes 

Changing your engine oil is usually something that mower owners don’t typically enjoy. It is just another task in your already busy schedule.  To keep your lawn mower performing well and your engine in good working condition, you must change your engine oil regularly. 

Skipping engine oil changes in your Craftsman can cause significant engine damage as I explain in depth here. 

Related Items 

Lawn Mower Checklist for Your Craftsman 

You have read why you need to check your engine oil level each time you mow your yard. It is important to take a few minutes and complete this checklist to ensure you remain safe and identify beginning signs of wear and tear, so you don’t cause further damage to your Craftsman lawn mower. 

Craftsman Riding Mower Guide 

I have put together a guide for your Craftsman lawn mower to help with questions on lawn mower maintenance schedules and operating your riding lawn mower. You can find it in “A Guide to the Craftsman Lawn Mower”.