Flash in fastboot mode. If you don't know how I suggest you use Google.
To flash the system.img you will need mfastboot found here. https://mega.co.nz/#!4wAkGJxJ!x5O6w-...evmENvv4iHBGS4
You will need to split up the system.img to use.. this is for advanced users only..
Download Links can be found on my website: http://www.graffix.nyc/motox.php
DO NOT MIRROR
Disclaimer: I am not responsible if you use this and brick your device or if your device blows up, implodes, flames start shooting from it or it kills your neighbor's dog. Flash at your own risk. I am not responsible.... It was the other guy... I swear....