The solenoid is normally closed, but when you apply 12 volts, it opens the ground path allowing the engine to run. Once the 12 volts is removed the solenoid closes to ground shutting off the magneto's power. One per magneto is required. PN 8134 can also be used in conjunction with a master cut off switch to "kill" the magneto - MSD or Mallory.
MSD Pro-Mags are engineered for a wide variety of racing applications. Each Mag is supplied with a durable cap and rotor that has been tested for performance. When space permits, upgrading to a larger diameter magneto cap can further prevent chances of crossfire. Also, if you're using a timing control to retard the timing, a Cap-A-Dapt is highly recommended because the retard affects the rotor pha..
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