A magnetic pickup is normally installed into the flywheel housing of an internal combustion engine, so that the starter ring gear acts upon it to generate a voltage pulse each time a gear tooth passes the end of the sensor. The frequency of this voltage is translated by the speed control into a signal that accurately depicts the speed of the engine (RPM).
How to Install and set the Gap Adjustment
Locate and remove the existing magnetic pickup on the engine.
Using a standard flat head screwdriver, orient the teeth of the flywheel so that a single tooth is centered on the hole.
Apply grease to the threads on the magnetic pickup.
Thread the magnetic pickup until it bottoms out directly on the centered flywheel tooth.
Once the pickup has bottomed out, turn the pickup back out exactly one half turn or 180 degrees back out.
Set the nut tight and connect the pickup to the engine harness.