Carburetor Adjustment - Stihl 029, 039 Service Manual

STIHL 029, 039
Top:
Correct position of torsion spring
(Zama)
Bottom:
Correct position of torsion spring
(Walbro)
- After fitting the choke shaft,
check that the torsion spring is
correctly positioned.
- Position choke shutter of Zama
carburetor so that the large bore
points toward the metering end
cover and the small bore toward
the lever on the choke shaft.
Top:
Fitting choke shutter (Zama)
1 = Large bore
2 = Small bore
Bottom:
Fitting choke shutter (Walbro)
1 = Round notch
2 = Indentation
Note: Fit the choke shutter of Walbro
carburetor so that the round notch
points toward the metering end cover
and the indentations face inward.
- Coat the fastening screw with
Loctite, - see 12.2, and tighten
down firmly.
- Install the carburetor - see 11.2.
11.5

Carburetor Adjustment

1 = High speed adjusting screw
2 = Low speed adjusting screw
3 = Idle speed adjusting screw
The carburetor has a standard
setting when it leaves the factory.
This is the optimum setting of the
high speed adjusting screw for the
barometric pressure and climatic
conditions at the factory (300 m/1000
ft above sea level). It ensures
maximum engine performance, fuel
efficiency and the highest possible
reliability.
Standard setting:
H = High speed adjusting screw
backed off 1 full turn
L = Low speed adjusting screw
backed off 1 full turn
If the carburetor has to be adjusted
from scratch, first carry out the
standard setting to obtain a starting
point for fine tuning.
If no tachometer is available, do not
turn the high speed adjusting screw
beyond the standard setting to make
the mixture leaner.
66