Valve float

Flutter valve called an uncontrolled operating state of a four-stroke engine, which can lead to engine damage.

It can occur in four-stroke engines that are operated with an excessive speed. During normal operation the movement of the valves is defined by the lobe curve of the cams. In the rising part of the curve, the valve is opened. The task of the valve springs is to push back against the open valves inertia valve back into their seats as soon as the camshaft permits. With increasing speed, this movement must always be faster, ie carried out with increasing acceleration. Above a certain speed, the valve springs are no longer able to apply the necessary force for such a movement. In the extreme case, the piston does not touch on time closing valve and causes serious engine damage. Engines with desmodromic valve control are better equipped against valve float.