the invention relates to a percussion tool having an internal combustion engine and a hammer mechanism that can be driven by the internal combustion engine by means of a transmission . a part of the engine housing , the transmission housing , or the impact hammer mechanism housing is enclosed by a cover . the cover is spaced at a distance from the remainder of the machine , so that a gap is present between the cover and the remainder of the machine . cooling air can flow into the gap at the lower face of the cover and flow back out via a flue and an opening . the components beneath the cover are thereby effectively cooled , even without an additional cooling air blower .