![background image](http://html1.mh-extra.com/html/stihl/fc-75/fc-75_user-manual_1378585037.webp)
•
Remove heat shield.
Important: Note installed
position.
•
Remove carburetor.
•
Remove gasket.
The parts are fitted in reverse
order.
- Tighten nuts to a torque of
4.0 Nm.
The maximum speed of the carbu-
retors is mechanically limited by a
cut-off valve. Unlike the case in
machines without cut-off valve, the
maximum speed cannot be set to
a value higher than that specified
when adjusting the carburetor.
The machine similarly cannot be
tuned to "top performance" on the
basis of its speed. The only thing
that is achieved by using an exces-
sively lean carburetor setting is
that it increases the risk of engine
damage without increasing either
the speed or the performance.
Standard setting
The standard setting must be
made first when adjusting the
carburetor for the first time.
- Carefully turn both adjusting
screws clockwise as far as
possible.
Then adjust as follows:
H = Back off high-speed adjusting
screw (1) one turn
L = Back off low-speed adjusting
screw (2) one turn
Minor corrections may be neces-
sary at great altitudes (mountain
regions), at sea level or when
changing the cutting attachment -
fitting a mowing head instead of
the metal cutting tool and vice
versa.
When correcting the setting of the
H = high-speed adjusting screw:
Use a tachometer!
Note: If a tachometer is not
available, the high-speed and low-
speed adjusting screws must not
be turned beyond the standard
setting to make the mixture leaner.
- Fit an approved cutting tool.
The following must additio-
nally be noted when changing
the mowing head:
- Set correct line length: every
nylon line must extend as far as
the blade on the deflector shield!
- Check and clean air filter if
necessary.
- Start engine and let it warm up.
H = Turn high-speed adjusting
screw clockwise in mountain
regions (leaner mixture) and
counterclockwise at sea level
(richer mixture).
The screw should only be
turned very little and slowly,
as engine performance
changes noticeably with the
slightest adjustment.
Adjustment
(two adjusting screws)
392RA117
2
H L
1
VA
392RA114
VA
TOP
392RA115
VA
392RA116
VA
37