Initial Inspection and Diagnostic Overview

(1) Check the valve face for correct contact. If incorrect, reface using a valve refacer. Valve should make a uniform contact with the seat at the center of valve face.
(2) It the margin exceeds the service limit. replace the valve.

Standard value:
Intake: 1.0 mm (0.039 inches)
Exhaust: 1.2 mm (0.047 inches)
Limit:
Intake: 0.5 mm (0.019 inches)
Exhaust: 0.7 mm (0.028 inches)





(3) Measure the valve's total length. If the measurement is less than specified, replace the valve.