Introduction to valve clearance
When the engine is running, the valve will expand due to the increase in temperature. If there is no gap between the valve and its transmission member in the cold state or the clearance is too small, in the hot state, the thermal expansion of the valve and its transmission member will cause the valve to be closed tightly, causing the engine to leak during the compression stroke and the power stroke. Gas, so that the power is reduced, even when it is serious, it is not easy to start. In order to eliminate this phenomenon, a certain gap is usually left in the valve and its transmission mechanism during the cold assembly of the engine to compensate for the amount of expansion of the valve after being heated. This gap is called the valve clearance.