Magneto to flywheer gap is the thickness of a business card. Be certain the kill wire is not shorting to anything metallic on the engine.
On the new briggs motors like you have a busted flywheel key wont cause lack of spark but will alter the timing pretty severely.
If the coil is found to be faulty, a magnetron coil from a sprint 375, newer 3.5hp briggs, classic 37 and a couple of others will fit so long as its not off a quantum engine. Should be pretty cheap either on eBay or a second hand one from your local mower shop.
Cheers Joe.
