White Smoke From
- Head gasket failure
- Faulty crankcase breather
- Worn out engine
Mower tipped over is the most common reason for white smoke. Usually, the customer turns over the mower to clean the deck or unclog the chute.
This allows oil to enter the cylinder, and when the mower is restarted, the oil burns and turns your yard into a 70s disco. Sometimes oil will also leak from the muffler.
The fix is simple, check the mower for oil, and let the engine idle until the smoke clears.
If your lawn mower is a tractor mower, white smoke usually means too much oil, carburettor fault, or blown head gasket. (more on this below)
Tipping the mower on its side for maintenance or cleaning causes oil to move into the cylinder.
When you fire up the mower the oil in the cylinder burns causing white smoke.
It will clear after a short while.
I hook the handlebars under a bench.
Turing your mower to the side is fine as long as you turn it with the carburettor side up.
A Case Of Too Much Oil
Too much oil will cause other problems, smoke, poor running, no running, leaks, engine damage.
Check out "How to check oil level".
Drain excess oil and check and top up if needed.
Gas in The Oil
The oil level will be overfull and stink of gas.
White Smoke & Dies
Remove the plug and clear the cylinder by turning over the engine with the pull cord.
Clean the plug before refitting.
Oil in the Gas Tank
Head Gasket Failure
Head gasket failure can cause white smoke.
This will only be an issue with ohv (over head valve) type engines, and will also depend on where the gasket fails.
Ohv engines are usually well marked with ohv on the front engine cover.
When it fails and depending where it fails, it will suck oil into the cylinder and blow gases into the crankcase.
Last on the list is engine wear or ring damage.
A compression test will confirm if you have internal damage.
This condition is rare.
Lawn mower smokes on start up? This is generally associated with an old mower, it's a sign of engine wear. But other possible causes include:
- Wrong oil type
- Wrong plug type
- Leaking carburettor float needle
- Crankcase breather fault
- Valve seals hard
- Head gasket failure