A new machine must be driven with restraint, and must not be worked hard until all working parts have settled down and are thoroughly free. The engine will not give its full performance until this has been achieved and the process of causing it to settle down and free off is termed " running in."

During this period hard pulling (" slogging ") at low speed on large throttle openings must be avoided and no attempt must be made to drive at constant high speed.

The throttle should therefore be opened only a small amount, and changes to lower gears made in good time, so that the engine may run lightly loaded.

It is not advisable to drive at a set low maximum speed or to keep to a regular speed, and provided that the speed in­creases on only a little throttle, as it will often do on running downhill, there is no need to hold the machine back.

After about one hundred miles use the engine should be accelerated for short sharp bursts of speed. The speed and duration of these short canters should be increased as the mileage increases and it will be found that the machine will usually be run in after about a thousand miles.