likely to be with the spark plug in that cylinder. The common troubles of spark plugs and the method of repairing them have been previously described. After the spark plugs have received attention the cables must be tested to make sure that the insulation is not injured in any way or that the metal terminals at the end of the cable do not come in contact with any metal parts of the motor or magneto. If the ignition fails suddenly, one can suspect a short circuit in the grounding cable, which is connected to the nut on the magneto contact breaker and which serves for switching the ignition off. This may be easily ascertained by removing the cable from the magneto and seeing if its removal enables the magneto to run correctly. A spark leaping the gap in the safety de

vice indicates a broken wire or one that has become disconnected either from the plug terminal or from the distributor terminal.

If the cables and plugs are in good condition and the engine works irregularly, it is apparent that the trouble is in the magnet if it is an ignition fault. In event of this, the most important thing to do is to make sure of the proper interruption of the primary current. The spring holding the cover of the contact breaker in place should be moved sideways and the brass cover taken off. It is then important to see if the screw D, Fig. 257, is tight. If this is found

Contact Breakers.

to be set up properly the next thing is to make sure that the contact breaker points are in contact when the bell crank lever is out of contact with the cam in the sides of the breaker box in the type DU-4 or away from the fiber cam rollers in the type D-4. It is also important that the platinum points are separated by the proper distance, about .5 millimeter, when the lever C F at A, Fig. 261, is in contact with the cam. If the points are too far apart they should be brought nearer together by loosening the lock nut on the adjusting screw shown at C, Fig. 261, and screwing it up to lessen the difference, or to screw it back and open the gap if it is not sufficient. The platinum contact points must also be cleaned, any dirt or oil being easily removed, as shown at Fig. 261, B, by gasoline squirted on them from a small hand oil can. In case the contacts are uneven, pitted or blackened, they must be smoothed with a jeweler's fine cut file. After continued use, if the platinum points have worn down the platinum-pointed screw must be removed. It is also important to make sure that the high tension current collecting brush, K, Fig. 256, is in contact with the collector ring, and that the conducting pencil N makes proper contact with the brush, against which it bears. This high tension collecting brush is indicated as P, and the collector ring as O, in Fig. 258. The interior of the distributor must be clean and free of metallic or carbonaceous matter. The distributing brush must bear positively against the distributor section and the interior of the distributor should be smooth and all contacts clean and bright.

Mention has been previously made of making sure that the screw which keeps the contact breaker assembly in proper relation with the armature shaft is tight, which calls for careful examination. If this screw is loose, the contact breaker assembly will not move in proper timed relation with the armature; in fact, it may not move at all, which will prevent the contact point from separating and which will also result in failure of the ignition. If everything appears to be all right about the magneto, the timing should be verified to make sure that the spark is occurring at the right time in the engine cylinders. It is easy to tell if the magneto is producing a spark of proper intensity by uncoupling a spark plug conductor and holding it a short distance away, not more than

Fig. 262.-Outlining Use of Gauges in Obtaining Correct Setting of Magneto Contact Breaker Points.

" from the terminal. If a magneto is functioning properly a spark will jump the air gap thus created.

At Fig. 261, D, the contact breaker and distributor construction of the Remy magneto is shown. It will be observed, in this case,

that the contact breaker assembly does not rotate, as in the Bosch, but that a rotating two-point cam is attached to the armature shaft and interrupts the contact between the points P by bearing against the end of the bell crank CF. The instructions given for care of the Bosch magneto apply just as well to this device. Realizing the importance of having the gap between the contact breaker points of the proper amount, the magneto manufacturers furnish gauges which are to be used for testing this gap. That shown at Fig. 262, A, is for use with the Eisemann magneto. With the contact breaker removed, as indicated at B, the contact points C-4 should be together as indicated. When the gauge is inserted in the hole C-7 it will indicate the correct amount the point should be separated. The gauge at Fig. 262, C, is merely a piece of thin sheet steel of the proper thickness which is used as indicated when the points are separated by the bell crank lever riding on the cam block.

Recharging Weak Magnets. After a high tension magneto has been in use for a time the magnets lose their strength and it is necessary to recharge them in order to restore the magneto to its full efficiency. When magnets are weak the resulting secondary spark will also be weak and the motor will not run regularly, no matter how carefully the device is adjusted. If the motor does run without misfiring it will not develop its full power if the magnets are weak. An electro-magnet designed to operate on 110-volt current is shown at Fig. 263, A. The core is of soft iron, 1" in diameter and 8" long. They are drilled at the bottom for a retaining screw, which is intended to keep them in contact with a base plate of steel 4" x 9". Two blocks of steel 134" x 2" x 4" are drilled to receive the cores, and have set screws in the side so they can be clamped tightly against the core to form polepieces. A brass tube about 1/16" thick at the side, having flanges at each end projecting over to hold fiber insulating plates as shown, may be turned to the dimensions indicated in a lathe or may be made up of sheet stock if desired. The hole through the center of the brass spool is of such size as to permit the core to fit freely in its interior. Besides this equipment, 22 lbs. of No. 20 B. & S. gauge insulated copper wire will be needed. Eleven pounds is wound around each brass tube, winding one coil in one direction and the other the