Stihl BR 550 Technical Guide - Page 17

Technical Information 08.2005 Page 17 5.5 Test the compression pressure In order to discharge the ignition voltage, the ZAT 3 5910 850 4520 ignition system tester must be mounted - high voltage shock hazard! . Remove the ignition system tester from the spark plug, and screw out the spark plug. . Screw in compression tester 5910 850 2000 (1) into the sparkplug hole. While using the ZAT 3, hold it only by the handle (4) or position it in a safe place. Fingers and other body parts must be at least 1 cm away from the spark window, high-voltage terminal, ground connection and ground terminal. . Pull the rewind starter quickly and forcefully (min. 1,000 rpm) as when starting. . Read the compression - the target is 7.5 ... 8.5 bar If the compression is under 7.5 bar . Check valve clearance, set if necessary and recheck the compression If the compression is still under 7.5 bar . Check the cylinder, valve seat, piston and piston rings for scoring and damage. . Connect the spark plug boot to the high voltage terminal (1). . Affix the ground terminal (2) to the muffler. . Set the knob (3) for the spark gap to approx. 2 mm. TI_08_2005_11_01_02.fm