Technical Information · issue 15 of 1995
Carburetor; Shroud
IssueTI 15/1995
Full text
Page 1 of 11
Technical Information
15.95
Brushcutters===============FS 108 - Series 4135
=======================FR 108 - Series 4135
Engineering Changes to Comply with Emissons Regulations
see also TI 41.94 and 47.94
&RQWHQWV
1. Carburetor
1.1 New spare parts
1.2 Service notes
1.2.1
1.3
Setting instructions for service
Setting instructions for user
2. Shroud (symbols for setting carburetor)
1.=Carburetor
New carburetors have been developed for these
models in order to fulfill the Emissions regulations.
The new carburetors differ from the existing 4
versions in the following areas:
• High speed screw (1)
• Low speed screw (2)
• Limiter caps (3) on high and 5
low speed screws
• Modified carburetor body (4) 2
The original and new adjusting screws have a 3
different thread profile and lead as well as different
shaped heads. A washer (5) is fitted between the
screw head and spring.
5 1
354TI001 K
The new limiter caps (3) are color-coded.
Assignment of color or cap to adjusting 3
screw:
Low speed screw High speed screw
White Red
)Technical Information 15.95 - Page 2
Carburetor adjustment on production line and in
service shop is performed without the limiter
cap.
90°
A special screwdriver is required for this purpose
(see service notes).
The limiter cap is firmly seated on the adjusting
screw during normal operation.======================================6===========6
The STIHL carburetor screwdriver can be used to
turn the adjusting screw. H L
354TI002 K
Once the cap has been fixed in place, the molded
stop (6) limits the screw’s range of adjustment to
1/4 turn.
If force is used to pull off the limiter caps, they are
destroyed or made unserviceable in the process.
Carburetors are adjusted without the limiter caps so
that any change to the carburetor setting after the
caps are fixed in position will not result in detrimental
variations. This means that the emission values
always remain below the emission limits
specified and provide the best possible engine
power.
The remaining range of adjustment is provided to
correct the setting in the case of unsatisfactory
running behavior or extreme changes in altitude,
humidity and outside temperatures.
1.1====New spare parts
1
3
5
4 6
3
7
354TI003 Gm
)Technical Information 15.95 - Page 3
Part Name Part No. Key Rem.
Carburetor C1Q-SK7; 4135 120 0601
including items 1 to 7:
High speed screw 4135 122 6700 1
Cap (red) 4135 121 2700 2
Washer (2x) 4135 121 8600 3 1)
Low speed screw 4135 122 6800 4
Cap (white) 4135 121 2701 5
Sealing plate 1125 121 0700 6 2)
Lever 4222 123 7300 7
All other parts as carb C1Q-SK5
5HPDUNV
1) One each for high speed and low speed screws
2) Will also be used in future in carb C1Q-SK5 (non-Emissions version) in place of 4129 121 0701
1.2===Service notes==========================================fo
The main differences between the new and
existing carburetors are in the area of the low
speed and high speed screws. For this reason
these service notes will concentrate on this
area.
The limiter caps are supplied loose=with replace-
ment carburetors. The caps are then pushed onto
the screws after the adjustments have been made.
1.2.1=Tools
Repairs and carburetor adjustments can be
performed ony if the following tools are 60 mm
available: (2")
Standard commercial screwdriver for turning
the adjusting screws without limiter caps.
The required dimensions of the blade and tip are
(0.078")
shown in the illustration.
2 mm
002TI005 K
)Technical Information 15.95 - Page 4
Installing tool for pushing the cap onto the
adjusting screw. This tool can be made up in 75 mm
the workshop from a standard commercial (3")
screwdriver - see the dimensions in the illustration.
5,6 mm 1,5 mm
(7/32") (1/16")
(0.04")
1 mm
(5/32")
4 mm
002TI006 K
1.2.2=Fitting adjusting screws and caps
1.2.2.1 Removal
• Pull the cap (1) off the screw.
This destroys the cap.
A new cap must be used. 1
354TI004 K
• Take out the adjusting screw (2) with washer
(3) and spring (4).
4 3 2
354TI005 K
)Technical Information 15.95 - Page 5
1.2.2.2 Installation
• &DUHIXOO\ screw home adjusting screw (2) with
washer (3) and spring (4) as far as it will go.
• Carry out carburetor adjustment -
see 1.2.3: "Setting instructions for service"
• Fit the limiter caps - 4
see 1.2.3.6: "Fixing the limiter caps" 3
354TI006 K
2
1.2.3=Setting instructions for service
$OZD\V use the procedure shown in the following
flow chart for carburetor adjustment.
Limiter caps that have been pushed fully home
cannot be reused after they are pulled off.
)Technical Information 15.95 - Page 6
Flow chart for carburetor adjustment
Carry out preparations
see 1.2.3.1
Carry out basic setting
see 1.2.3.2
Adjust idle speed
see 1.2.3.3
Carry out full-load speed setting
see 1.2.3.4
QR
Running behavior OK?
see 1.2.3.5
\HV
Remove ERWK caps
Fix the caps
see 1.2.3.6 see 1.2.2.1
QR
Running behavior OK?
see 1.2.3.5
\HV
End of carburetor adjustment
)Technical Information 15.95 - Page 7
1.2.3.1 Preparations
Engine speeds must be checked with a
tachometer.
• Check the air filter and clean if necessary.
• Inspect the spark arresting screen and clean
or replace if necessary.
• Mount STIHL Autocut or Polymatic head -
adjust length of lines so that they extend as far
as line limiting blade on the deflector.
1.2.3.2 Basic setting
• Starting with the adjusting screws against their
seats - open both screws (+ and /) two full
turns.
• Start the engine.
• Carry out full-load speed setting, H L
see 1.2.3.4.
354TI007 K
1.2.3.3 Adjusting idle speed
• Use a screwdriver with a 2 mm (5/64") tip.
• Adjust maximum idle speed with the low speed
screw (/).
LD
• Turn low speed screw (/) counterclockwise
until engine speed drops about 300 rpm. L
• Set engine speed to 2,800 rpm with the idle
speed screw (/').
354TI008 K
1.2.3.4 Adjusting full-load speed
• Run engine at full throttle=~nd turn high
speed screw (+) carefully clockwise until no
further increase in engine speed is obtained
====within=the=speed=r~nge=from=6,500 to
8,500 rpm.
If the required speed range is not reached,
H
vary the length of the cutting line until the
speed is correct.
• Rotate high speed screw (+) counterclockwise
354TI009 K
until engine speed drops about 100 rpm.
)Technical Information 15.95 - Page 8
1.2.3.5 Checking running behavior
• Open throttle several times and check that
engine accelerates smoothly - the engine
must also run smoothly at idle speed.
1.2.3.6 Fitting and fixing limiter caps
• Shut down the engine
• Fit both limiter caps (1) loosely on the
adjusting screws (2) so that the stops are
positoned as shown (see arrows).
354TI010 K
• Use the installing tool to carefully push the
limiter caps over the adjusting screws (2). 2
002TI011 K
1
1.3=====Setting instructions for user
These instructions are exactly the same as those
in the owner’s manual (chapter "Adjusting the
Carburetor").
The carburetor comes with a standard setting.
• Check air filter and clean it if necessary.
• Check spark arresting screen
and clean it if necessary.
• Mount the cutting head and trim
lines to correct length:
Lines must extend as far as line
limiting blade on the deflector.
)Technical Information 15.95 - Page
A= =Standard setting
If it is necessary to readjust the carburetor from
scratch, first carry out the standard setting.
• Start the engine.
• Turn the high speed adjusting screw (+) H L
and the low speed adjusting screw (/)
counterclockwise (richer) or as far as limiter
caps allow.
354TI007 K
If you don‘t have a tachometer, do not set the
high speed adjusting screw any leaner by turning
it beyond the standard setting.
B =Warm up the engine.
• Warm up the engine by running it for about
1 minute at full throttle and then return to
idle speed.
C =Setting idle speed
It is usually necessary to change the setting of
the idle speed adjusting screw (/') after every
correction at the low speed adjusting screw (/). LD
Cutting tool rotates when
====engine is idling
• Turn the idle speed adjusting screw (/')
counterclockwise until cutting tool stops
rotating - then back off screw about another
354TI008 K
half turn from that position.
D =Setting maximum engine speed
====With cutting head
• Use a tachometer=to set the high speed
adjusting screw (+) to obtain the highest
possible engine speed. From that position,
turn the high speed adjusting screw (+) 1/8 H
counterclockwise (richer) or as far as stop.
====With metal cutting tool
The setting must not be changed.
354TI009 K
Avoid risk of engine damage which can be
caused by lack of lubrication and overheating!
)Technical Information 15.95 - Page 10
Engine stops while idling
• Turn the idle speed adjusting screw (/')
clockwise until the engine runs smoothly -
a cutting tool or blade must not rotate.!
LD
354TI013 K
Erratic idling behavior, poor acceleration
• Turn the high speed adjusting screw (+)
and the low speed adjusting screw (/)
counterclockwise (richer) or as far as the
limiter caps allow.
• Carry out step C. H L
If running behavior does not improve, repeat steps
A to D.
354TI007 K
2.=====Shroud
The carburetor adjusting screws on Emissions-
approved machines allow a user adjustment of
maxK=90 degrees.
For this reason the symbol for "open 1 turn"
is not applied to shrouds for machines with H L
Emissions approval.
In order to standardize parts, the setting symbol
will not be applied to any machines or shrouds in
future.
354TI012 K
LD
Only shrouds without the setting symbol may
be used for machines with Emissions approval.
)Technical Information 15.95 - Page 11
6XPPDU\
Part Name Original New Key Rem.
version version
Shroud 4135 080 1600 4135 080 1600 1)
Modification to be introduced
- on Emissions machines: from start of production
- on non-Emissons machines: in progress
5HPDUNV
1) Unmodified version of part will be supplied until existing factory stocks are exhausted
Last Technical Information on models FS 108: 37.94
FR 108: 05.95
Waiblingen, June 09, 1995 Andreas Stihl - D1/MTK-na
© 1995 Andreas Stihl Technical Documentation Page 2 of 11
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