Stihl BR 550 Technical Guide - Page 7

Technical Information 08.2005 Page 7 1.6 Decompression system The automatic decompression system reduces the compression upon starting and hence the required pull on the starter rope. Cam disk at low speed (starting): 1.7 Carburetor . All-position diaphragm carburetor with independent idle . The range of the high-speed adjusting screw (H) and the low-speed adjusting screw (L) is limited by limiter caps (approx. 3/4 turn). This limitation ensures greater operating safety and maintenance of future exhaust emission levels . Accelerator pump for faster and spontaneous acceleration (see 5.3). . Choke knob with integrated starting throttle position . Decompression cam (1) projects and actuates the lever (2) . This lengthens the valve opening time, which reduces the compression Cam disk when the engine has started: 1.8 Ignition system . Microprocessor-controlled with ignition timing adjustment . Low power-up threshold 1.9 Air filter . Large-area paper air filter for long filter service life . Easily accessible 1.10 Muffler . Two-chamber muffler with spark arresting screen, depending on the market concerned. 1.11 Flywheel . The centrifugal mechanism retracts the decompression cam (1) - this cancels the effect of the decompression cam . Weight-optimised geometry TI_08_2005_11_01_02.fm