Why is there no spark to the spark plug on your walk behind MTD mower with 4.5 horse Briggs Stratton engine which is a single speed having no throttle?

Answer 1

You don't indicate an age. Has it been stored inside or out in the weather? My first guess is that the flywheel has some rust on the magnetized areas. The magnets spinning magneto creates the electricity to cause a spark when the points open. Take off the recoil starter. The are two magnetized areas on the flywheel. Get some emery cloth (do NOT use sandpaper) and clean up these magnets. The magneto sits just far enough away from the flywheel that a dollar bill will slide easily between the two. No more no less. Throw away the gas in the tank and refill with fresh. That's probably the biggest culprit to a non-starting engine.