Stihl FS 80 Service Manual

11FC 75, FC 85, FH 75, FS 75, FS 80, FS 85, HL 75, KM 85, KW 85
Condition Cause Remedy
Poor acceleration Idle jet too lean Turn low speed screw (L) counter-
clockwise (richer), no further than
stop
Main jet too lean Turn high speed screw (H) counter-
clockwise (richer), no further than
stop
Inlet control lever too low
(relative to correct installed
position)
Set inlet control lever flush with top
of carburetor body
Inlet needle sticking to valve seat Remove inlet needle, clean and
refit
Connecting bore to atmosphere
blocked
Clean the bore
Diaphragm gasket leaking Fit new diaphragm gasket
Metering diaphragm damaged or
shrunk
Fit new metering diaphragm
Carburetor floods,
engine stalls
Inlet needle not sealing. Foreign
matter in valve seat or cone
damaged
Remove and clean or replace inlet
needle, clean fuel tank, pickup
body and fuel line if necessary
Inlet control lever sticking on
spindle
Free off inlet control lever
Helical spring not located on nipple
of inlet control lever
Remove inlet control lever and refit
correctly
Perforated disc on diaphragm is
deformed and presses constantly
against inlet control lever
Fit new metering diaphragm
Inlet control lever too low
(relative to correct installed
position)
Fit new inlet control lever

Stihl FS 80 Specifications

General

Engine Type	2-stroke
Displacement	25.4 cc
Cutting Diameter	420 mm
Shaft Type	Straight
Starter	Recoil
Sound Power Level	106 dB(A)
Fuel Capacity	0.44 liters
Vibration Level	4.5 m/s²