Valve clearances

The correct setting of valve clearances is very important, as they largely determine the operation of the engine. If the valve clearances are too large, the engine will be noisy and the efficiency of the engine will be reduced as the valves open too late and close too early. A more serious problem occurs if the valve clearances are too small, as the valves cannot close fully on a hot engine, which can cause serious engine damage.

These engines have hydraulic tappets that are automatically controlled by the pressure of the lubrication system to compensate for the gap between the camshaft lobe and the corresponding valve stem. Therefore, regular checking and adjustment of valve clearances is not required. However, it is essential that a good quality engine oil of the recommended viscosity is used and that the engine oil is changed at the recommended intervals. When starting a cold engine, there is a slight delay until the engine oil pressure equalizes in all parts of the engine. especially in hydraulic tappets. Therefore, valves can "knock" approximately 10 seconds, after which the knocking disappears. This is the normal state of affairs, provided that all pushers continue to operate silently.

After the engine has not been started for several days, the valves may "knock" for a longer time, as almost all of the oil drains from the top of the motor and bearing surfaces. At this time, care must be taken not to damage the engine, that is, to avoid a sharp change in the engine operating mode until all the pushers are filled with engine oil. When the engine warms up, the fast idle speed (maximum 2000 to 2500 rpm) should not be exceeded for 10-15 minutes, or until valve banging stops.