The starter motor in located under the left footrest you can see in the clip.
If I am not mistaken, the starter is out of Honda magna 750, which he reversed the rotating direction,
and it connects directly to the crank via a directional coupler. (Like a ratchet action)
This is as much as I recall, but I will try to get more info.
He does not use the exhaust valve lifter when starting, (The bike has a good compression)
And the battery is 12V, 12 or 14 AH.