Remove valve.
Clean the guide bush with a cylindrical reamer.
Insert the valve into the guide sleeve from the side of the combustion chamber.
Check its play when the valve is moved laterally in both directions.
To check, attach a steel ruler or put a dial indicator. The play must not exceed 0.5 mm.
If increased backlash is detected, machine the valve guides and install valves with an increased stem diameter (service station work).
Caution: When machining or replacing guide bushings, the valve seats must also be machined.