Manual 814-1 OPERATION No D. 210-0: Checking and adjusting the ignition Op. D. 210-0 NOTE: It may be noted on figure 2 that when the engine turns at a speed of less than 700 I.p.m. approximately the advance point read on the stroboscope is less than 12° When the engine is idling it is possible for the mark on the drive pulley to take the position shown in figure 5. Ill, PRINCIPLE OF THE METHOD OF MEASURING THE ADVANCE BY USE OF STROBOSCOPIC LAMP.