57-78 Sportsters (except XLC and XLCH)

• The ignition system has two circuits; (1)-the primary and (2)-the secondary circuits. ¹⁾

1. The primary circuit includes the battery, switch, primary coil and the breaker points.
2. The secondary circuit consists of the secondary coil and the spark plugs.

• The breaker cam and contact points open and close the low tension circuit between the battery and the ignition coil.
  (which causes the coil to produce high voltage discharge to the spark plugs)
• The circuit breaker also times the discharge for proper engine firing.

• The circuit breaker ignition was not factory installed on XLCH engines.
• However, they provide consistent lighting for riding at night.
• The magneto has been changed out to a circuit breaker ignition on many XLCHs

Circuit breaker ignition on a 70 model XLCH 2)