Bolens Mower Smoking (White, Blue or Black)? Causes & How to Fix It

Smoke color tells the story on a Bolens mower. White or blue smoke means oil is burning in the combustion chamber — usually from overfilling or tipping the mower the wrong way. Black smoke means it's running too rich, typically a dirty air filter or flooded carburetor.

Let the engine cool before checking oil; disconnect the spark plug boot before servicing.

Get your exact fix

Enter your model for an instant diagnosis tuned to your exact Bolens — ranked causes, the right parts, and a step-by-step repair guide. Bolens (MTD) mowers run Briggs or Powermore engines on budget-friendly walk and riding decks.

Most likely causes

01Burning oil (white/blue smoke)
45%
Overfilled crankcase or a mower tipped on its side pushes oil past the rings/breather into the cylinder.
How to check: Check the dipstick for overfill and note the smoke — white/blue that worsens on throttle-up or tilt is burning oil, and usually clears after a few minutes if it was a tip-over/overfill.
Reference: Engine service manual — lubrication & seals
02Running rich (black smoke)
35%
A clogged air filter or a stuck carburetor float floods the engine with too much fuel.
How to check: Black smoke with a raw-fuel smell is too rich — pull the air filter (cleaner burn without it = clogged filter) and check the plug for wet black soot.
Reference: Engine service manual — fuel & carburetor
03Blown head gasket
12%
A failed gasket lets oil into the chamber; often paired with power loss.
How to check: Run a compression test, or look for oil weeping along the head-to-block seam — low compression on that cylinder with steady smoke points to the head gasket.
Reference: Engine service manual — cylinder & compression
04Worn piston rings
8%
High-hour engines burn oil past worn rings — the one non-trivial repair here.
How to check: If compression is low and a teaspoon of oil down the plug hole temporarily raises it (wet test), the rings are worn — high hours and steady blue smoke back this up.
Reference: Engine service manual — cylinder & compression

Parts you may need

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How to fix it

7 steps

1
Check the oil level and how it was stored
5 min
Pull the dipstick and confirm the oil isn't overfilled — an over-full crankcase is the single most common cause of white/blue smoke. Also note if the mower was recently tipped on its side; if so, run it a few minutes and the smoke often clears as the excess oil burns off.

The rest of the repair

02Correct the oil level if overfilled
03Replace or clean a fuel-soaked air filter
04Inspect the carburetor float for sticking (black smoke)
05Run the engine to burn off residual oil after tipping
06If smoke persists, test compression for gasket/ring wear
07Replace the head gasket if compression is low on one side

The full guide adds the smoke-color diagnostic chart, compression numbers, and head-gasket replacement steps. Run the free diagnosis above to unlock it for your model.

Frequently asked

Why is my Bolens mower blowing white smoke?

White or blue smoke is burning oil — most often from an overfilled crankcase or from tipping the mower on its side. Check the oil level first; the smoke usually clears once excess oil burns off.

Is it safe to run a Bolens mower that's smoking?

Brief smoke after tipping or overfilling is harmless once it clears. Continuous heavy smoke means oil or fuel is entering the cylinder — stop and diagnose before it fouls the plug or overheats.