OK, some things to check:
1. CHI-COM Spark Plugs suck I have had 100% failure of every one I have owned. Try a new name brand spark plug.
2. IF you have an ignition switch, Ohm it out to see if it is good
3 .Ohm out all of the ignition wiring for broken wires or open switches.
4. Check the gap on the flywheel to the ignition coil
5. If you have points,make sure they are adjusted properly and not burnt/eroded away.
6. IF you have a Condenser with the points, replace it. These fail on a regular basis on old engines.
7. Are you generating a Spark? Place the spark plug lead close to a non-painted engine or frame part about a 1/8-1/4" away from the metal and with the spark plug removed,have someone pull the starter rope fast. You should see a spark. Hold the rubber wire,not the metal end.You will get shocked if it is working. ( ignition switch on)
If you going to replace parts, the Condenser and the spark plug would be my first. Coils can fail but it is not all that common. I have never seen a magnet go bad. I guess it could happen,but never in my life time to me.
We need more details on your engine maker and age of the engine/HP rating.