2585386 - Introduction - TIMING SYSTEM

There are the same number of suitably positioned cams as there are valves to operate. At the front, it is prepared for the fitting of the toothed pulley, through which the movement of the crankshaft is received, by means of a suitably tensioned belt.1, Oil seal2, Camshaft3, Adjustment shim4, Tapppet5, Cotters6, Upper shim spring7, Spring8, Oil seal9, Lower shim10, Inlet valve11, Exhaust valve12, Valve guideThe camshaft is the component which, through the cams, opens the valves for the required time. Since in 4 stroke engines the working cycle takes place during two revolutions of the crankshaft, whilst the valves have to open only once during the cycle, the camshaft only has to rotate once; therefore, the toothed pulley fitted on the camshaft will have twice the number of teeth as the pulley fitted on the crankshaft. therefore, the toothed pulley fitted on the camshaft will have twice the number of teeth as the pulley fitted on the crankshaft.