Water entrance valve = Stopcock??? Check that, it's possible to 'mow' it off, and it's under mains pressure on a BIG main. Firehose stuff if it blows, can't turn the house water off if it bends of breaks.

Take Bobert's advice, but it may be difficult to start as movers get some of their flywheel effect from the blade. You have to get them spinning fast, to start without.
In the worst case, borrow a mower whilst yours is in the hands of a mower specialist. Or even a go-cart specialist, as some classes use the B&S motor. It's not huge money for a new crank.
The go-cart guy I know mix-and-matches B&S parts to get the most powerful (but untuned, as the rules demand) motor, and he has spares for Africa!