As I understand it, you need two XH-G1s to sync timecode using the Jack Pack studio connectors.
But here's a trick we use to sync timecode on our two XH-A1s. It MIGHT work with an A1 and a G1.
1. Set the cameras side by side and turn them on.
2. Rotate the LCD monitors so that you can see them while standing in front of the cameras.
3. Use the remote from one of the cameras to simultaneously set the timecode on both cameras to Free-Run: Menu > Signal Setup > Time Code> Count-Up
4. Make sure to reset the Start Value to zero.
The timecode will now start counting up continuously whether or not the cameras are recording. Be aware that if you start and stop your recording multiple times, you will have timecode breaks on your tape. If you are capturing in Final Cut Pro, simply set the User Preferences to make new clip on timecode break. This trick has been incredibly helpful to us on multiple occasions. Hope this helps.