Not sure exactly which mounts you have in there, but it does appear you are missing some parts.
Here is a pic of the Dave Brown mounts for a 4 stroke. It is available at central hobbies.
I have a plane that had a YS 140 mounted on wood rails with this style of mount, but it kept breaking the mounts due to rotational stresses. It's not so much the vibration but the rotational effect the YS engines exert when they shake that these type of mounts are not designed to handle.