The valve of qq car is broken. What happened to the new car?

The valve of qq car is broken, and the new car is boring because:

1, valve clearance adjustment is too small: when the car is hot-started, the valve cannot be completely closed or the valve is not tightly closed, resulting in power loss and burning of the valve sealing belt, leading to serious failure.

2. The engine timing is wrong and the valve is not well run-in.

3. The sealing performance of the valve oil seal is not good.

4, throttle, air intake, valves and other parts of the carbon deposition increased.