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15 Adjusting the Carburetor
Thinning Brush and Cutting small Trees with a Circular Saw 
Blade
► Before starting the cut, accelerate the engine to full 
throttle. To reduce the risk of kickout, always apply the 
circular saw blade to the right of the tree as shown in the 
illustration, using steady pressure throughout the cut.
► When felling small trees, maintain a distance of at least 
two tree lengths from the nearest coworker.
Observe all applicable laws, regulations, standards and 
ordinances.
14.2 Adjusting the Nylon Line
WARNING
To reduce the risk of personal injury from unintended 
activation, always shut off the engine before manually 
adding or adjusting the nylon line.
AutoCut Mowing Heads
► While the cutting attachment is rotating, tap the rotating 
mowing head on the ground.
Approximately 1.2 in. (30 mm) of fresh nylon line will be 
advanced with each tap. The line limiting blade in the 
deflector trims the mowing line to the proper length.
The bump feed mechanism will not advance additional line 
if the mowing line is shorter than 0.1 in. (25 mm). To feed 
additional line manually:
► Shut off the engine.
► Depress and hold the button on the mowing head.
► Pull out the mowing line by hand.
► If the mowing line cannot be pulled out to the required 
length, install a new spool of line.
SuperCut Mowing Heads
Fresh nylon line will be advanced automatically without 
tapping on ground. The line limiting blade in the deflector 
trims the mowing line to the proper length.
The automatic feed mechanism will not advance additional 
line if the mowing line is shorter than 0.1 in. (25 mm). To 
feed additional line manually:
► Shut off the engine.
► Depress and hold the button on the mowing head.
► Pull out the mowing line by hand.
► If the mowing line cannot be pulled out to the required 
length, install a new spool of line.
STIHL recommends keeping nylon line in a water bath for at 
least 12 to 24 hours before use to increase its useful life.
15.1 STIHL M-Tronic Engine Management System
The STIHL M-Tronic engine management system 
electronically controls the ignition timing and fuel metering in 
any operating condition, factoring in altitude and fuel quality. 
This system provides optimum performance, whether you 
are just starting to work or resuming after a break. Manual 
carburetor adjustments are no longer required. The 
carburetor does not have adjusting screws.
15 Adjusting the Carburetor