AboutEric A. Jones Expertise Lawnmower Repair . Certified Master Service Technician from B&S. Have 13 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.
Experience Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. I received a scholarship from the Air Force and am currently pursuing another degree.
Question Iam experiencing problem of a third magneto failure in two weeks on my 1997 Sears lawn tractor with a 19.5 HP twin B&S engine. Magneto failed for first time after 9 years of flawless operation of mower engine. My certified mechanic diagnosed problem as a failed magneto, replaced same and after four hours of cutting, it failed. Maybe, he thought, the new replacement was faulty, so another was installed. Again, after four hours, it too has failed i.e no spark.Everything else was checked out at time of first replacement. Could the problem be the lack of a ballast resistor in the supply line to the magneto, as was surmised in a discussion back on June 9, 2006 between your expert Allen Kirkland and a person who had a problem that sounds just like mine. I don't want to keep getting new magnetos which my mechanic has thus far replaced without additional charge (except for the first one) without some idea of what the underlying problem might really be. Any help would be appreciated. Jim MacRae
Answer That new of a mower does not use an actual magneto. Magnetos were actually old mechanical devices.
However, the ignition module/coil is a solid state electronic device as far as the spark triggering is concerned.
So, there is no ballast resistor used in the ignition system. However, you key switch or another electric part that is allowing 12 volts DC to reach the coil.
There is a small wire connected to the coil. This wire is connected to the primary winding side of the coil. If there is voltage present on this wire it could be frying the windings.
When you turn the key to the off position the switch grounds the primary side of the winding and stops spark for the engine to shut off.
You can use a voltmeter to test. Dis-connect the small wire, turn the key to the run position and see if the is 12 volts DC on the wire.
If there is this is your problem. If you don't measure any voltage you can follow the small wire to engine block connection. Assemble the engine re-connecting the small coil wire. Start the mower and then use a volt meter to see if there is any voltage at the engine block connection.
