Valve is one of the important parts of 4-stroke engine gas distribution mechanism, and its working performance has a direct influence on the normal engine power's. Due to the hot gas environment, the valve working conditions are extremely bad, it's very easy to cause abnormal wear and accidental damage.
Generally speaking, the following conditions are often found:
Corrosion wear of valve cone and neck;
Ablation of Valve
Wear, bending and fracture of valve stem