MAKE-AND-BREAK IGNITION
An engine equipped with the make-and-break ignition system is always provided with a conducting bar across the top or side of the cylinders, called a bus bar, connected with the source of current, and each igniter is connected to it through a switch. If one of the cylinders fires regularly, it is an indication that the current is being generated properly, and that no time need be wasted in examining the generator. By means of the switches, the igniters may be tested individually by cranking the engine with one switch closed and the others open. When the clutch is disengaged the engine should run on one cylinder, and if this is the case, the igniter on the line of the closed switch is shown to be in good condition. The opening of this switch and the closing of the next will give a comparison when the engine is again cranked, and if explosions occur, the igniter points may be adjusted until the two cylinders work equally well. If the cylinder does not operate, the stationary igniter point should be withdrawn and its contact examined; this should be bright and clean. The movable point should be worked by hand, to determine whether the joint is stuck or the spring weak or broken.
If none of the cylinders show signs of explosions, the connections should be examined to make sure that they are secure. On systems employing a magneto alone, the wiring consists of a single wire from the magneto to the bus bar, and the shorter wires from there to the igniters. These wires are clearly visible, and any loose connections or broken wires may be detected without difficulty. If the connections and wiring are in good condition, the fault may be located in the magneto, or, if it has recently been dismounted, its incorrect setting in relation to the crank shaft. (See Appendix.)
If the ignition system proves to be in proper working order, attention may be paid to the carburetor and its connections.