Stihl BR 550 Technical Guide - Page 15

Technical Information 08.2005 5.4.3 Determine top dead centre Page 15 5.4.4 Check valve clearance The cam disk cover must be installed to "Check the valve clearance" and "Set the valve clearance". . Rotate the crankshaft until the tip of the flywheel (arrow) is flush with the ignition coil as shown The piston is now at the top dead centre, valve overlap, or in top dead centre, ignition. . Insert setting gauge (1) between rocker arm (2) and valve stem (3) - the setting gauge must produce a slight suction effect when it is pulled through The valve clearance must be adjusted if it is found to be too large or too small. . Turn the crankshaft back and forth a few degrees - if the rocker arms and valve stems move up and down (see arrows), the piston is in the top dead centre for valve overlap . Rotate the crankshaft once more until the tip of the flywheel is flush with the ignition coil. Rocker arms and valve stems do not move and the piston is now in the top dead centre for ignition. . Turn the crankshaft back anticlockwise approx.1/4 turn and then slowly turn it clockwise again until the tip of the flywheel is lined up with the ignition coil. The crankshaft must be turned backwards in order to eliminate the flank backlash from the timing gear. TI_08_2005_11_01_02.fm