Symptoms
- Air filter feels wet or oily to the touch
- Engine runs rich, smokes, or is hard to start
- Oil visible inside the air filter housing
- Recently transported or stored the equipment on its side
Likely causes
- CommonOverfilled crankcase oilExcess oil can be pushed into the air intake through the breather system.
- CommonEquipment stored or transported on the wrong sideTipping some small engines the wrong direction lets oil drain into the air filter or cylinder.
- PossibleClogged or failed crankcase breatherThe breather regulates crankcase pressure and can fail, forcing oil into the intake.
- Less commonWorn piston rings allowing excess blow-bySignificant internal wear can push oil past the rings and into the breather system.
What to do
- Check the oil level and drain any excess back to the correct fill mark.
- Clean or replace the oil-soaked air filter; a foam filter can sometimes be washed, dried, and re-oiled per manufacturer instructions.
- Check the manual for the correct side to tip the engine if you need to lay it down for any reason.
- Inspect the crankcase breather tube for clogging or damage.
- Wipe out the air filter housing of any accumulated oil.
- Run the engine briefly after cleanup and watch for continued oil migration into the filter.
- If oil keeps appearing in the filter with correct oil level and no tipping, a small-engine shop should check for worn rings or a failed breather.
Tools and parts
- Replacement or cleanable air filter
- Rags
Small engine air filterSearch: “small engine air filter replacement”
When to call a pro
A small-engine shop can check for worn piston rings or a failed breather if the problem keeps recurring with correct oil levels.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.