The upgrade process is simple and you do not need root permission to install the update. Keep in mind that the below guide is only for Moto G Dual SIM (XT 1033), DO NOT try to update on other models using this method and file.

Important: Backup your contacts, SMS, WhatsApp messages, email and other data using apps like Titanium Backup. Instruction:

  1. Download the official Android 4.4.2 firmware (for Asia) from this link and transfer it to your phone’s memory. Important: Verify filename and MD5 checksum value of downloaded file. – Filename: Blur_Version.14.85.4.falcon_umtsds.AsiaRetail.en.0 3.zip – MD5 checksum value: 44f72f52d72e9e73e3f5c5d6447c2bf5
  2. Turn off your phone and enter into recovery menu. To do so, first, press “volume down” button and then press “Power button”. Hold down both buttons for a few seconds.
  3. Now, select “Recovery” using volume down button and then choose “Update from sdcard option”, then press the Power button.
  4. Select the zip file (you have downloaded earlier), and then press the power button to begin the update. It will take not less than 5 minutes to complete. Once the update process completed, you will get an “install from sd card complete” message. Now reboot your Moto G and enjoy KitKat features. (Source)