Adjustments By User - Stihl FS 94 Instruction Manual

Adjusting idle speed
– Adjust engine idle speed with a
tachometer or the STIHL MDG 1.
Adjust specified engine speeds
within a tolerance of ± 100 rpm.
1. Turn the low speed screw L
counterclockwise or clockwise
to obtain the highest engine idle
speed.
If the engine speed is not between
3,100 rpm and 3,300 rpm, abort the
procedure, set the engine speed to
3,200 rpm with idle speed screw LA
and start again with step 1.
2. Use the
idle speed screw LA
) to set the engine speed to
3,200 rpm.
3. Use the low speed screw L
to set the engine speed to
2,800 rpm.
.
1
This completes fine tuning of the
high speed screw H (1) and low
speed screw L (arrow).
The settings of the high speed
screw H and low speed screw L
cannot be changed by the user.
78

10.5.2 Adjustments by User

The new carburetors ensure the
engine receives an optimum fuel-air
mixture in all environments and
operating conditions. For this
reason it is only possible to correct
the engine idle speed with the idle
speed screw LA (arrow).
Always perform the following steps
before carrying out any
adjustments:
– Troubleshooting, b 3.4
– Check the working tool, adjust if
necessary.
– Check the air filter (felt element)
and clean or replace if necessary
– see instruction manual, b 10.1
Check running behavior:
The engine must accelerate
smoothly when the throttle is
opened and run uniformly at idle
speed.
Adjusting idle speed
Basic setting and fine tuning of
adjusting screws has been carried
out.
– Warm up the engine.
Engine stops while idling
– Turn the idle speed screw LA
clockwise until the working tool
starts running, then turn it back
1 full turn.
Working tool runs when
engine is idling
– Turn the idle speed screw LA
) counterclockwise until the
working tool stops running, then
turn it back 1 full turn.
Erratic idling behavior, poor
acceleration
– Check basic setting and fine
tuning of adjusting screws, re-
adjust if necessary or service the
carburetor, b 10.5.1, b 10.4
Fine Tuning for Operation at High
Altitude
Motor does not run satisfactorily.
– Check basic setting and fine
tuning of adjusting screws, re-
adjust if necessary or service the
carburetor, b 10.5.1, b 10.4
Series 4149 Powerhead