What brand engine? Some have points & condenser, others use electronic ignition...Purchase an inexpensive spark tester. HIGH VOLTAGE SHOCKS ARE DANGEROUS.You can remove the spark plug and ground the threaded end. Pulling or spinning the engine while using normal starting procedures for that engine you should see the spark jump from the electrode to ground. If no spark is observed usually the magneto coil is bad. Spark plugs do go bad. Sheared flywheel key. Defective SAFETY switch,these are located at various points on all mowers...
Ricky
May 2009