TROUBLES
If there is an abrupt failure of ignition, it is probable that the primary is short-circuited, and this can only occur on the wire that leads to the short-circuiting switch, for the other parts of the primary circuit are inclosed and protected against injury.
In case of the missing of one cylinder only, the trouble will usually be found in the plug, which may be short-circuited by a carbon deposit, or because the intense heat of the spark has fused the metal, resulting in the formation of a globule of metal between the spark points. Too great a distance between the points, more than one sixty-fourth of an inch, will prevent the passing of the spark, which will then be seen in the safety spark gap.
A miss in different cylinders may be due to defective insulation of the wires, but if these are in good condition the fault may be looked for in the magneto. The place where trouble is usually experienced is in the interruptor, which may become dirty, or the contacts may be worn down or loosened from the vibration. Fouled contacts in the distributor may also lead to a miss-fire, and this will be corrected by wiping the parts with gasoline. If all of these parts have been examined and found correct, it is inadvisable to examine further into the magneto, for inexperienced handling will be likely to injure the delicate parts. It is better to place it in the hands of a man whose shop is equipped for the work.