Stihl BR 550 Technical Guide - Page 13

Technical Information 08.2005 Page 13 5.2 Standard setting with limiter caps The limiter caps must not be removed when making the standard setting. . Turn the high-speed adjusting screw (H) and low-speed adjusting screw (L) anticlockwise as far as possible (max. 3/4 turn). See instructions for use, "Setting the carburetor," to set the carburetor for users. 5.4 Valve clearance The valve clearance must be checked once after approx. 139 hours of operation and adjusted if necessary. The valve clearance may only be checked and adjusted when the engine is cold. Kit 4282 007 1001 "Parts for adjusting valve clearance" must be used for this purpose. The kit comprises a setting gauge, O-ring and gasket. 5.4.1 Preparatory steps . Remove the shroud with rewind starter . Remove the lines from the ignition module . Remove the air guide shroud. . Unscrew spark plug 5.3 Accelerator pump The carburetor is equipped with an accelerator pump. The pump piston (1) is located in the cylinder bore (a) behind the throttle shaft (2) and is held in the idle position by a compression spring (3). When opening the throttle shutter, fuel is also sent through the main nozzle into the the air cone (Venturi valve) providing fast and spontaneous acceleration. . Clean area around valve cover . Remove screw (1) . Remove O-ring (2), valve cover (3) and gasket (4) . Determine top dead centre TI_08_2005_11_01_02.fm