What is the cause of oil leakage from the engine throttle?

Oil pan gasket is damaged or screws are loose, and oil leaks.

Oil drain plug gasket of oil pan is damaged, missing or loose, resulting in oil leakage.

The gear gasket is improperly assembled, damaged or the screw is loose and leaks oil.

The engine bracket plate is deformed or the gasket is not tightly sealed, resulting in oil leakage.

Valve cover gasket is not tightly sealed and leaks oil.

Crankshaft front oil seal is damaged and leaks oil.

The crankshaft rear oil seal is damaged and leaks oil.

The oil return thread at the rear end of the crankshaft is blocked by dirt and leaks oil, the oil return thread is improperly processed or the coaxiality of the thread journal and the oil seal seat hole is out of tolerance.

The back cover of cam bearing never leaks oil.

The rocker arm chamber cover or push rod chamber cover is not tight, resulting in oil leakage.

The oil radiator is not tightly sealed and leaks oil.

The oil filter is not tightly sealed and leaks oil.

The bearing hole of distributor housing is not tightly sealed, resulting in oil leakage.

Oil pump gasket damaged or screw loose, oil leakage.