BRIGGS & STRATTON 163CC 725EXI SERIES Leaking Oil From Muffler

Cylinder Head Gasket

The most common mechanical failure on these OHV engines is a blown head gasket between the cylinder and the pushrod cavity. This breach allows the piston to create a vacuum that pulls oil from the crankcase into the combustion chamber, where it is then expelled as liquid or partially burnt oil through the exhaust valve and into the muffler.

Crankcase Breather Assembly

The breather valve regulates internal crankcase pressure. If the internal reed valve fails or becomes gummed up, it can no longer separate oil mist from the air, causing liquid oil to be pumped out of the breather tube and into the air cleaner or exhaust assembly, leading to visible leakage from the muffler.

SKU: 596161

Air Filter

When oil is forced into the exhaust system due to tipping or overfilling, it almost always saturates the air filter through the breather tube simultaneously. A saturated paper filter restricts airflow, creating a rich condition that increases vacuum in the cylinder, further pulling oil into the combustion path and out the muffler.