I have a 16.5 ovh Briggs in an MTD. The mower started and ran fine the last few mowings. However, now it will not fire. The starter will turn the motor for a few seconds and then it will "bog" down. I can turn the motor by hand past the "hard" part of the engine cycle and the starter will turn the engine over again for a few revolutions.

The engine has spark. When the spark plug removed to check spark the starter spins the engine very easily. I have used starter fluid in the carb and still can not get the engine to fire.

I have checked the alignment of the flywheel with the shaft to see that the magnet on the flywheel passes the coil at the appropriate time and seems to be okay to me.

What next?