A machine for the preparation of liquid products via capsules comprising a delivery assembly with a preparation chamber, which comprises a first part and a second part. The second part of chamber comprises an injector device, which is configured for introducing a preparation fluid into a capsule and has a hollow body and includes a first body part and a second body part. Defined between the two body parts is a chamber, housed in which is a perforation device having at least one front perforation element that is axially aligned to a respective through hole, defined in a front wall of the second body part of the injector device. The second body part is slidable, against the action of elastic means, from an advanced position, in which the at least one perforation element does not project substantially beyond the front wall, to a retracted position, where the at least one perforation element projects substantially beyond the front wall. The elastic means comprise a bending spring that extends in a direction transverse to the direction of axial sliding (X) of the second body part with respect to the first body part.