Page:Motors and motor-driving (1902).djvu/351

Rh independently of the carburetter. Another plan is to procure some boiling water, and after soaking rags in it to wrap them round the carburetter till the petrol is warm enough to vaporise sufficiently. In many of the new designs of bicycles, however, spray-type automatic carburetters are being fitted. No doubt these have certain advantages over the surface type, but with their use the necessity of seeing that no dirt or foreign matter gets into the petrol tank becomes an urgent question. They should be placed as near as possible to a source of heat to prevent them from becoming frozen in cold weather.

In the majority of motor cycles electrical ignition of the jump spark type is adopted, although in a few cases the magneto arrangement is being employed. The escape of the electric current or the premature running down of the battery is one frequent cause of trouble where dry batteries or accumulators are used. It may result from loose electrical connections, bad contacts, and short circuits. If two of the terminals of the wires get connected with a film of moisture, a short circuit is the inevitable outcome: hence extreme care should be taken when riding for a considerable time in the rain. The rider should frequently test the accumulator with a voltmeter to see that the necessary charge is there, or if a dry battery is used, test the amperemeter, and he should always carry a spare battery. Then he should see that all contacts and connections are firmly made, and that every wire connection is covered and properly insulated. There may be trouble through the platinum points of the contact-breaker getting worn down or dirty with oil, or the platinum, on what is known as the 'trembler' (whether it trembles or not is a debatable point), becomes loose and causes jumpy progression of the machine. The remedies are obvious: clean the contact points or replace with a new 'trembler.' If the cautions here given are observed there should be freedom from electrical troubles between the battery and the sparking plug.

Sparking plugs are often a source of worry, but a friend has travelled 11,000 miles and only required three plugs. Apart