> - Blocked CCV (crankcase ventilation) valve or hose.
> - Incorrect crankcase breather setup (e.g. missing or damaged components, incorrect routing, etc.).
> - Excessive blow-by (compression gases leaking past the piston rings) - this can be caused by worn-out piston rings or scratched cylinder walls.
Excessive oil level:
> - Overfilling the oil reservoir beyond the recommended level can cause oil to enter the air cleaner through the breather system.
Defective air cleaner:
> - A faulty or damaged air cleaner assembly, or using a non-recommended air filter, can allow oil droplets to pass through and enter the engine's intake.
Incorrect carburetor settings:
> - Incorrect float level or fuel jets in the carburetor can lead to excess fuel entering the combustion chamber, which can result in unburned fuel and increased blow-by.
Worn-out valve seals:
> - Worn-out or damaged valve seals can allow excessive oil to enter the combustion chamber and increase the oil droplets in the blow-by gases that are routed to the air cleaner.
Cylinder head issues:
> - Issues with head gaskets, valve cover gaskets, or other sealing components can result in oil leaks near the air cleaner.
