Why is there gasoline coming out of the pipe on the cylinder head at the motorcycle fuel filler door?

As soon as the motorcycle stepped on the accelerator, gasoline came out of the pipe on the cylinder head, which was caused by filling the cylinder.

The cylinder was flooded because the oil level of the carburetor was out of control, and too much gasoline flowed directly into the cylinder through the intake pipe and then infiltrated into the crankcase of the engine. If it can be started at this time, too much gasoline and engine oil in the cylinder will be ejected from the cylinder head or other pipes that can ventilate the engine when the valve is filled.

The solution is to check and clean the carburetor, adjust the oil level of the carburetor, and check whether the float needle is worn or stuck, resulting in lax closing. If it is a scooter, check whether the switch of the negative pressure tank is damaged and the oil flows into the engine from the oil suction pipe. Check the oil condition in the engine. If the gasoline is mixed, change the oil before starting the engine.