How to Test a Small Engine for Spark
If your small engine isn't starting, you'll need to diagnose many issues including the spark plug. This video walks you through the steps of how to test for a spark using a spark tester.
The only problem with replacement is, the machine has to be almost disassembled. Watch where the parts are removed from. Assembly should be easy. Keep small parts in a small tray for they get lost very easy. Fuel lines should be replaced at this time for they should be very easily broken. Make sure the air gap is set at 0.012 or you will have no spark.