How To Drive A Motorcar
A Key To The Subtleties Of Motoring

THE QUESTION OF SPARK GAP the magneto itself, and if the width between the elec- trodes is too great, then, owing to the compression of the gas in the cylinder, the spark will refuse to jump the plug gap and select the one in the safety gap in the magneto itself, for preference. Also remember, therefore, that because the spark jumps quite readily across the gap when the plug is laid on the top of the engine, it by no means follows that it will do so when screwed down in position, as the gaseous pressure is greatly increased, and the greater the pressure the greater the current requisite to jump Distributor of magneto taken apart showing brush and contacts a given distance between the electrodes. This fact may be more completely grasped when it is stated that the actual safety gap in the magneto itself, where there is no air compression, is usually set 12 or 13 times as wide as the width of a plug gap. If the plug is really badly sooted up, so that ordinary rinsing in petrol does not appear to clean it, then the centre electrode of the plug itself may easily be re- moved so that both portions may be cleansed separ- ately. Cleaning the Distributor In the upper little cover-case at the end of the magneto is to be found the distributor, and if the 45