2. Valves can only be lapped with fine grinding paste. For rotation, a suction cup is installed on the valve disc. Grooving during lapping can be avoided by frequently removing and turning the valve further.
Attention! After lapping, the grinding paste must be completely removed.
3. The lapping process is controlled by applying to the contact surface "Preussischblau" or "Bleiweiss", as well as with fuel. Insert the valves, fill the combustion chamber with fuel, fuel must not flow out to the valve guide. Otherwise, the lapping process must be repeated.