ORIGINAL: Sneasle
I thought you were not supposed to prime with electric starters because you risked hydro locking the engine? Is it possible you are flooding the engine by priming it (or at least it has way to much fuel in it) and it is taking a few seconds for it to spit out enough of the fuel to come up to the right mixture?
He's hand flipping it during the priming. He wouldn't be able to turn it over easily by hand if it were going to hydraulic lock.
He's been priming until the fuel JUST gets to the nipple on the carb. Big engines with the carb half open do not draw fuel well when being motored by the starter, not enough vacuum.