Small Engines (Lawn Mowers, etc.): no fire, briggs and stratton, fly wheel

Question
Tom, I am a contractor that ownes several loaders and trucks and am able to keep them all running ,it as been thirty yrs since i worked on a small gas engine so i need some help.I have a mower with a briggs and Stratton 18hp twin model 42a707. It has been running poorly for awhile, wich I thouoght was due to carburation....It would run fi9ne for short time and then stal.....I would play with choke and throttle sometimes getting it to restartt right away and  so0metimes just haveing to walk away and then come back later and it would start. But now i cant get it to start.and after  alittle troubleshooting. I have found that I have no spark. The mower does have a deadman switch  that is functioning properly. Does ythis engine have a coil? UIf so do you think that that is the problem or are there more possibilities?...I thank you for your time and your help
Greg


Answer
Greg, as long as all safety switches are working properly then I believe your in need of a coil. All safety switches work by grounding the spark, and stalling the engine buy doing such. You will have to remove the top components of the engine to expose the coil, like the shroud. sometimes on rare occasions the fly wheel magnets, and or the coil pick-up can become rusted due to lack of use, it then will produce at times a weak spark, or no spark, make sure they are not rusted. If your coil has a small wire attached remove it, and check for spark again, this small wire is the wire the safety switches use to ground out the coil. If still no spark continue to remove the coil after checking that it was tight, and the gap was correct, the gap should be the thickness of a business card. If these conditions are correct remove the two screws securing the coil to the engine. turn the fly wheel magnets away from the coil, and bolt the new coil down, insert a business card between the fly wheel and the coil, loosen the hold down bolts a little and turn the fly wheel till the magnets suck the coil between the card and the magnets, and re-tighten the bolts, turn the flywheel away and remove the card. Now check for spark again, both with the small wire attached, and without. Now reassemble the shroud, and what ever else was removed to gain access to the coil. .......Tom