1. Measure the free length (A) of valve spring with vernier calipers.
If the measurement is less than the allowable limit, replace it.
2. Put the valve spring on a surface plate, place a square on the side of the valve spring.
3. Check to see if the entire side is in contact with the square.
Rotate the valve spring and measure the maximum tilt (B).
If the measurement exceeds the allowable limit, replace it.
4. Check the entire surface of the valve spring for scratches.
If there is any defect, replace it.