I mean technically you can but the MMX is designed for 1/8 scale motors on 6S max and the Spektrum 1250Kv is more for 1/7-1/5 scale rigs on 8S max. So, if you're going to use it in an 1/8 scale rig or maybe a 1/7 scale rig on 6S then it would probably be fine. If you want to run 8S or you're trying to use that combo in something bigger than a light 1/7 scale rig then no, that combo wont work.