Small Engines (Lawn Mowers, etc.): Cant get a spark, visible sign, handle bar

Question
I have an older ('86) Murry with a Briggs Quantum 4.0hp engine.  I haven't used it in quite a while.  I replaced oil,gas and spark plug but it won't start.  Don't see any spark from plug in dark.  I took the armature-magnito off and cleaned it all.  When putting it back on, should it touch the metal wheel, rest against it or is there a gap?  Any ideas on spark issue?  Ways to test?  It worked a few years back....but.  

Answer
Use a business card to set the gap. Turn the flywheel till the magnets on the flywheel are in front of the mag slide the card between and loosen the mag so that the magnets pull the magneto and sandwich the card. Tighten the mag back down. Turn the flywheel to remove the card, be carfull not to pinch a finger.  check the kill wire that runs from the under side of the magneto to the kill switch on the flywheel brake. its usually green or black. The brake is operated by the bail lever on the upper handle bar make sure the wire is not chaffing and grounding out against the engine block. after you get it all back together have some one give it a pull while you ground the side of the plug against the engine. the plug must be grounded or it wont spark. may want to wear glove r hold it with a pair of pliers so you dont Zap yourself. If it doest spark try a different plug. Sometimes plugs just go bad without any visible sign that its a bad plug. if a new plug doesnt spark I would say the magneto is bad and needs to be replaced.