Hi Lastlaugh, good on you for posting the photos. Please photograph every aspect of every step, not for our benefit but for your own, in three months from now, when you have found spares, you will have a visual record of how it all goes back together.
I am a little concerned that a single 12 volt battery will not have enough grunt to start an ST2. My ST2 requires 24 volts (two batteries) to get it fired up. You could probably overcome this by fitting two solenoids with a timer to drop the decompression levers (start one cylinder and use that to start the second). It may be that the starter built in to your generator head is a more powerful unit and all you will need is a high output 12 volt battery.
Keep us posted.
Bob