1. Cylinder Head Gasket: The cylinder head gasket is a thin seal between the cylinder head and the engine block. If this gasket is damaged or worn, it can cause oil to leak from the engine.
2. Oil Pan Gasket: The oil pan gasket is a seal between the oil pan and the engine block. If this gasket is damaged or worn, it can cause oil to leak from the bottom of the engine.
3. Valve Cover Gasket: The valve cover gasket is a seal between the valve cover and the cylinder head. If this gasket is damaged or worn, it can cause oil to leak from the top of the engine.
4. Crankshaft Seals: The crankshaft seals are located at the front and rear of the engine. These seals prevent oil from leaking from the engine when the crankshaft is spinning. If these seals are damaged or worn, they can cause oil to leak from the engine.
5. Cam Chain Tensioner Gasket: The cam chain tensioner gasket is located near the top of the engine. This gasket prevents oil from leaking from the engine when the cam chain is tensioned. If this gasket is damaged or worn, it can cause oil to leak from the engine.
6. Oil Drain Plug: The oil drain plug is located at the bottom of the engine. This plug prevents oil from leaking from the engine when it is drained. If this plug is not tightened properly, it can cause oil to leak from the engine.
7. Oil Filler Cap: The oil filler cap is located at the top of the engine. This cap prevents oil from leaking from the engine when it is filled. If this cap is not tightened properly, it can cause oil to leak from the engine.
8. Breather Tube: The breather tube is a hose that connects the engine to the air filter box. This hose allows air to enter the engine and prevents oil from leaking from the engine. If this hose is damaged or disconnected, it can cause oil to leak from the engine.
It is important to note that these are just some of the possible oil leak points in a GY6 150cc engine. If you notice an oil leak, it is important to have the engine inspected by a qualified mechanic to determine the source of the leak and to have it repaired.
