IF the starter motor was suspect then by shorting out the terminals you would create a circuit and the stater would work..creates a few sparks tho.
It sounds like the solinoids merrily clicking away in your you tube video.
Drain the petrol..maybe put some kinda system cleaner in the tank,like REDEX and refill.
I would change the spark plug too.
Buy yourself the best quality battery you can afford ...and use the bike!!