It looks like the Sky Viper takes an 8mm x 20mm motor (aka: 0820). Those are easy to find, Google "0820 coreless motor"). The Ares looks like either a 0716 (not quite as easy to find as the 0820's) or a 0816 (even less easy to find). My suggestion would be measure the diameter and length of the motor on that one to confirm. There are only a few standard sizes of those coreless motors.