Small Engines (Lawn Mowers, etc.): Won;t start or spark, problem thanks, spark plug

Question
Trying to start mower lst time this spring.
Replaced spark plug, cleaned carburator, new gas but no spark.
I put on the dethatch blade. At first try to start,that blade was loose and did alot of clunking, mower sputtered and died. I tightened the blade and did the above trouble shooting, but since then it won't even spark.  Where can I look for the problem? Thanks much

Answer
If the blade was loose, it's likely that when you tried to start it, the flywheel key got sheared.  When the flywheel key shears, you may lose spark (especially if it has points ignition) or the spark timing will be far enough off that the engine won't run.  Hope this helps.