Clearance Setting for a Lawn-Boy Mower Coil

Lawn-Boy Ignition

• The ignition in a Lawn-Boy engine consists of a magneto, a coil, breaker points, condenser and a spark plug. The spark plug requires a high-voltage current to ignite vaporized fuel vapors in the combustion chamber. Magnets built into the engine flywheel rotate around the magneto. This creates a high-voltage electrical current that is passed to the coil.

Coil Function

• The electrical current from the magneto is not sufficient by itself to provide the necessary voltage to the spark plug. For this reason, the magneto current is passed to the primary coils of the ignition coil. At the same time, the breaker points are opening and closing, causing the current in the primary coil to cycle on and off. The act of the current being shut off abruptly in the primary coils causes a high output of voltage in the secondary coils of the ignition coil. This is the current that provides voltage to the spark plug through a high-tension insulated wire.

Coil Adjustment

• The primary coil gets its voltage as the magnetically charged current from the magneto sweeps past the coil. If the coil is out of adjustment, the spark plug might not receive the proper voltage needed to ignite the gasoline vapors. The gap between the heels of the coil and the flywheel magnets needs to be .010 inch. This gap can be checked with a nonmetallic shim available from Lawn-Boy parts dealers. Because magnets are involved, a metal spark plug tool cannot be used to the check the coil gap.

Other Factors

• If your Lawn-Boy engine is not running properly, there are components other than the coil that should be checked and adjusted, as well. If the breaker points are dirty, corroded or out of adjustment, the coil will not receive the proper voltage. A faulty ignition condenser might cause electrical arching across the points, which will shorten the life of the points. Even if all other components are working as intended, the engine might not fire with a dirty or improperly gapped spark plug.