Check the plate thickness of the valve by means of a caliper with the nonius.

Standard thickness of inlet valves: 1,05–1,45 mm.

Minimum admission: 0,5 mm.

Standard thickness of final valves: 1,20–1,60 mm.

Minimum admission: 0,5 mm.

If thickness of a cylindrical part of a plate is less than minimum admissible value, replace the valve.