Stihl FS 55 R Product Instruction Manual - Page 34

English Adjusting the Carburetor The carburetor comes from the factory with a standard setting. This setting provides an optimum fuel-air mixture under most operating conditions. With this carburetor it is only possible to adjust the high speed screw within fine limits. Standard Setting N Stopping the Engine N Mounting the cutting attachment N Check the air filter and replace it if necessary. N Have the spark arrestor checked - see "Inspection and Maintenance by Dealer" HL LA N Turn high speed screw (H) counterclockwise as far as stop (no more than 3/4 turn). N Turn the low speed screw (L) carefully clockwise as far as stop, then turn it back 1.5 turns. N Start and warm up the engine if necessary. N Adjust idle speed with the idle speed screw (LA) so that the cutting attachment does not rotate. Fine Tuning A slight correction of the setting of the high speed screw (H) may be necessary if engine power is not satisfactory when operating at high altitude, sea level or after changing the cutting attachment. 233BA050 KN Rule of thumb: Turn the high speed screw (H) about one quarter of a turn for every 1000 m (3300 ft) change in altitude. Conditions for adjustment Adjust the high speed screw (H) only if you are using a mowing head, making sure the cutting lines are full length (as far as the line limiter blade on the deflector). If a metal cutting attachment is mounted, use the standard setting and adjust the high speed screw (H) as described above under "Rule of thumb". N Carry out the standard setting. N Start the engine and, with the mowing head mounted, warm it up for about 3 minutes. N Open the throttle wide. At high altitude N Turn the high speed screw (H) clockwise (leaner), no further than stop, until there is no further noticeable increase in engine speed. At sea level N Turn the high speed screw (H) counterclockwise (richer), no further than stop, until there is no further noticeable increase in engine speed. It is possible that maximum engine speed may be reached with the standard setting in each case. 32 FS 55, FS 55 C, FS 55 R, FS 55 RC