STOP , caution… just a word of warning when checking the spark on an opposed twin motor so as not to damage the ignition coil. These motors have what is known as an ungrounded coil. The circuit for the high voltage ( the coil secondary winding) is completer by way of each spark plug gap and the engine block. To help understand… lets say that when the high voltage is built up in the coil and is to be discharged to the spark plug (s) , it follows this path to make a complete circuit. From one end of the secondary coil winding >>> to one of the spark plug wires >>> jumps the spark plug gap >>> to the engine block>>> to the other spark plug BODY >>> jumps that gap >>> to the other wire >>> and finally back to the opposite end of the coil secondary winding. Excuse the unprofessional explanation , but that is how it works. The CAUTION… when checking the spark or pulling over the motor it is critically important the this complete circuit be maintained to prevent damage to the coil from internal high voltage discharge. For example, when checking the spark on one plug , be sure that the other spark plug wire is connected to either an installed plug or grounded to the engine. If one or both wire is not connected to ground, coil damage may ( will ?) occur..
Joe B
