In the late 70's I bought a victa mustang 2-stroke, In all that time I only ever replaced the plug about three times, three pulls and starts each and every time, still going well today, so impressed with this mower I bought a modern 4-stroke (B&S motor)
and have found the old 2-stroke has more torque, power, and doesn't clog up with grass under the blades and in the hull.
But alas you live and learn, the reason for this post is to point out that the intake filter on the 4-stroke is way down low, If your cutting long damp grass or you gave it a rinse the last time you used it, the filter could be moist and simply flood the engine.
I'm looking at perhaps a mod for this problem, raising the inlet up on the bar? will post back when I have a fix.