Seeing smoke pouring out of your lawn mower can be alarming. A smoking engine often indicates a problem that needs fixing. But not all smoke signals serious issues. By understanding what causes smoke in lawn mowers and how to address it, you can get your mower back to normal.
This comprehensive guide will cover:
- Common reasons lawn mowers blow smoke
- What different smoke colors signify
- Steps to troubleshoot and fix a smoking mower
- Preventative maintenance to avoid smoke issues
What Makes Lawn Mowers Blow Smoke?
Several underlying issues can cause smoke to emit from your mower’s exhaust area. Here are some of the most common culprits:
1. Clogged Air Filter
A blocked air filter prevents proper airflow into the carburetor and engine. This can cause incomplete fuel combustion and smoke. Mowers used in dusty/debris-filled conditions are prone to clogged filters.
2. Faulty Carburetor
The carburetor mixes air and fuel for ignition in the cylinder. If the carburetor is improperly calibrated or malfunctioning, it can send the wrong air-fuel ratio into the engine, resulting in smoke.
3. Burning Oil
Oil that leaks into the combustion chamber and burns along with fuel will produce smoke. Causes include overfilled oil, damaged seals, and tipped mowers.
4. Damaged Fuel System
Issues like cracked fuel lines, faulty injectors, or bad gasoline can send excess fuel into the engine. This can burn incompletely and cause smoke.
5. Engine Wear
Worn piston rings, cylinders, and other engine components allow oil and combustion byproducts to escape into the exhaust and form smoke.
What Does the Smoke Color Mean?
The color of the smoke can indicate which part of the mower could be malfunctioning:
Thick black smoke usually points to an issue with the air intake or fuel system. Insufficient air and too much fuel causes incomplete combustion.
Blue or White Smoke
These smoke colors signal burning oil. Oil is leaking past seals into the combustion chamber. Overfilled oil, tipped mowers, and bad gaskets are common culprits.
This often occurs at startup as accumulated unburnt fuel is expelled. It should go away as the mower warms up. Persistent gray smoke can indicate worn engine parts.
Watching smoke color on startup versus while mowing can help narrow down the cause.
How to Troubleshoot and Stop Lawn Mower Smoke
Here are steps to locate and fix the source of smoke in your lawn mower:
For black smoke:
- Check/replace the air filter if it’s clogged with debris.
- Inspect fuel lines and injectors for cracks or damage.
- Test and recalibrate the carburetor settings as needed.
- Try fresh fuel in case old gas is the culprit.
For white/blue smoke:
- Check oil level and drain any excess that could leak into the cylinder.
- Allow mower to run 10+ minutes upright to burn off leaked oil.
- Ensure the mower isn’t tipped beyond a 15 degree angle when in use.
- Replace a damaged head gasket or o-rings/seals to prevent oil escaping.
For persistent smoke:
- Remove spark plug and check its condition. Replace if excessively fouled.
- Do a compression test to check for potential engine wear.
- Have a small engine mechanic inspect for intake, fuel system, or internal engine issues.
Be sure to allow the mower to fully cool before conducting inspection and repairs. Wear protective gloves and eye wear when working near hot areas.
How to Help Prevent Lawn Mower Smoke
Along with proper troubleshooting, following good preventative maintenance can help avoid many mower smoking issues:
- Change oil and filters as specified in the owner’s manual.
- Check/replace air filters when they appear dirty.
- Inspect fuel lines, injectors, seals for wear or leaks.
- Clean debris from around engine, belt, and vent areas.
- Drain old gas and use fresh 89+ octane fuel with fuel stabilizer added.
- Allow mower to fully cool before proper storage at end of season.
- Avoid overfilling the oil reservoir.
- Keep mower upright when moving and avoid tilting past 15 degrees.
- Follow factory sharpening guidelines for blades to prevent overworking the engine.
Frequently Asked Questions
Thick black smoke is very concerning as it can signal lack of proper airflow or a fuel system problem. It demands immediate inspection and repair.
This is somewhat normal as oil residue burns off. But if it continues smoking more than 30 seconds into use, it likely indicates an issue.
Yes, leaked oil reaching the hot engine can burn and create smoke. Find and fix the leak, and drain excess oil.
Run the mower upright for 10 minutes to burn off any oil that leaked into the cylinder when tipped.
White smoke from burning oil is common and repairable. Allow the mower to fully cool, drain excess oil, and replace any damaged gaskets or seals.
If smoke persists after trying the above troubleshooting, it likely has deeper issues requiring a mechanic’s diagnosis.
Smoke coming from your lawn mower can definitely cause concern. But in many cases, it simply indicates routine maintenance or minor repairs are needed. Follow the troubleshooting tips above to stop your mower blowing smoke and keep it running smoothly.
Checking for leaks, changing fluids regularly, and keeping debris out of the engine will go a long way towards preventing issues. And don’t forget to browse our guide for the best gas lawn mowers when it’s time to upgrade your smoking mower!