Stihl 38 User Guide

FS 38
English
19
Remove the mowing head.
STIHL AutoCut
NHold the mowing head steady.
NUnscrew the cap counterclockwise.
STIHL PolyCut
NBlock the shaft.
NUnscrew the mowing head 
counterclockwise.This engine is certified to operate on 
unleaded gasoline and the STIHL two-
stroke engine oil at a mix ratio of 50:1.
Your engine requires a mixture of high-
quality gasoline and two-stroke air 
cooled engine oil.
Use mid-grade unleaded gasoline with a 
minimum octane rating of 89 ((R+M)/2) 
and no more than 10%...

FS 38
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20 STIHL MotoMix uses STIHL HP Ultra 
two-stroke engine oil suited for high 
performance engines.
For further details, see 
www.STIHLusa.com/ethanol
If not using MotoMix, use only STIHL 
two-stroke engine oil or equivalent high-
quality two-stroke engine oils that are 
designed for use in air cooled two-cycle 
engines.
The use of non-seasonal gasoline 
blends may increase the potential for 
pressure to build in the fuel tank during 
operation. For example, using a winder 
blend during the...

FS 38
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21
Controls
1Stop switch
2Throttle trigger lockout
3Throttle trigger
4Tongue of throttle trigger
5Catch
Positions of stop switch
6I – normal run position – the engine 
is running or can start
70 – Stop – engine off – the ignition is 
switched off
Starting
NMove the stop switch toI.
NPress down the throttle trigger 
lockout and hold it there.
NSqueeze the throttle trigger until the 
catch on the tongue (4) can be 
engaged on the housing (arrow).
NNow release the throttle trigger, 
tongue and...

FS 38
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22 Cranking
NPlace the unit on the ground: It must 
rest securely on the engine support 
and the deflector.
To reduce the risk of accidents, check 
that the cutting attachment is not 
touching the ground of any other 
obstacles.
NMake sure you have a firm footing, 
either standing, stooping or 
kneeling.
NHold the unit firmly on the ground 
with your left hand and press down 
– thumb under the fan housing – do 
not touch the throttle trigger or 
trigger lockout.
NOTICE
Do not stand or kneel...

FS 38
English
23 NSet choke lever to e and
Nmove the stop switch to I, lockout 
lever and throttle trigger to the 
starting throttle position.
NStart the engine by pulling the 
starter rope briskly – 10 to 20 pulls 
may be necessary.
If the engine still does not start
NMove the stop switch to0.
NRemove the spark plug – see 
"Spark Plug".
NDry the spark plug.
NCrank the engine several times with 
the starter to clear the combustion 
chamber.
NRefit the spark plug – see "Spark 
Plug".
NMove...

FS 38
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24 NRemove the felt element (3) from 
the filter housing (4) and replace it – 
knock out or blow out as a 
temporary measure – do not wash.
NReplace damaged parts.
NFit the felt element (3) in the filter 
housing (4).
NClose the filter cover so that it snaps 
into position.Exhaust emissions are controlled by the 
design of the fundamental engine 
parameters and components (e.g. 
carburation, ignition, timing and valve or 
port timing) without the addition of any 
major hardware.
General...

FS 38
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25
Standard setting
NTurn high speed screw (H) 
counterclockwise as far as stop (no 
more than 3/4 turn).
NTurn the low speed screw (L) 
carefully clockwise as far as stop, 
then turn it back 3/4 turn.
Adjust idle speed
NCarry out the standard setting.
NStart and warm up the engine.
Engine stops while idling
NTurn the idle speed screw (LA) 
slowly clockwise until the engine 
runs smoothly – the cutting 
attachment must not rotate.Cutting attachment rotates when engine 
is idling
NTurn the...

FS 38
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26 If the engine is down on power, difficult 
to start or runs poorly at idling speed, 
first check the spark plug.
Install a new spark plug after approx. 
100 operating hours or earlier if the 
electrodes are badly eroded/corroded.
The wrong fuel mix (too much engine oil 
in the gasoline), a dirty air filter and 
unfavorable running conditions (mostly 
at part throttle etc.) affect the condition 
of the spark plug. These factors cause 
deposits to form on the insulator nose 
which may...

FS 38
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27 If engine running behavior is 
unsatisfactory even though the air filter 
is clean and the carburetor is properly 
adjusted, the cause may be the muffler.
Have the muffler checked for 
contamination (carbonization) by your 
servicing dealer.
STIHL recommends that you have 
servicing and repair work carried out 
exclusively by an authorized STIHL 
servicing dealer.For periods of about 3 months or longer
NDrain and clean the fuel tank in a 
well ventilated area.
NDispose of fuel properly...

FS 38
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28
Adjusting Nylon Line
STIHL AutoCut
NHold the rotating mowing head 
above the ground – tap it on the 
ground once – about 3 cm (1.2 in) of 
fresh line is advanced.
NThe blade (1) on the deflector (2) 
trims surplus line to the correct 
length – avoid tapping the mowing 
head more than once at a time.
Line feed operates only if both lines still 
have a minimum length of 2.5 cm (1 in).
If the line is shorter than 2.5 cm (1 in):
WARNING
To reduce the risk of injury, always shut 
off the...