Note. Standard values for all checks are given in the section «Service data and specification» at the end of the chapter.
Valve sizes
Check the geometric dimensions of each valve.
If the values obtained are not correct, replace the valve with a new one and check the tightness of the valve against the seat.
Clearance between stem and valve guide
Valve stem diameter by micrometer (A) measure the diameter of the valve stem.
Valve guide inner diameter
Measure the inside diameter of the valve guide with a bore gauge.
Clearance between stem and valve guide
(Clearance between stem and valve guide) = (Guide bush inner diameter) - (Valve stem diameter).
If the value obtained is out of specification, the valve and/or sleeve must be replaced.
Valve seat seat
After verifying that the dimensions of the valves and guides correspond to the nominal values, check the correct seating of the valve in the seat.
Apply a thin layer of Prussian Blue to the valve face, press the valve face against the seat, but do not rotate the valve. Then remove the valve and inspect the seat and valve face.
If the ink is imprinted around the entire circumference of the valve seat, the valve guide and valve seat are aligned.
A. Fine.
B. Abnormal.
Otherwise, grind the chamfer and check again. Replace the valve seat with a new one if the correct seating of the valve cannot be achieved.
Valve spring misalignment
Using a bench square, check that the valve spring is perpendicular to the seating surface. While rotating the spring, measure the maximum value of the gap between the upper edge of the spring (IN) and square (A).
If the measured value is out of specification, replace the valve spring with a new one.
Spring Sizes and Elasticity Characteristics
Check the generated load at a certain height of the valve spring, using a special stand.
If at least one of the values obtained is not correct, replace the valve spring with a new one.