Make sure your phone working on .629,
1.Flash repacked .608 sbf
(Never Try Full .608 SBF !!!)
2 .Download tool PetesMotorolaRootTools or SuperOneClick extract all and run.(Just like rooting .608）
Note : - FIRST - Please Enable USB Debugging , Then connect cable for usb type Charge only
3.Install app otarootkeeper(Can be found in Play Store,it's free),backup su, unroot.
4.Reboot to Motorola Recovery, Wipe, apply .629 OTA update.zip,reboot.
5.install otarootkeeper app again,restore su
Check your device, it should rooted
ATTENTION: Reapply .629 update is very important, when you flashed our repacked .608 sbf, your device is working on a unstable hybrid rom
Here's where my friend posted: