Stihl FS 94 Instruction Manual page 14

Condition
Working tool runs when engine is
idling
Engine speed drops quickly under
load – low power
Series 4149 Powerhead
Cause
Engine idle speed too high
Clutch spring stretched or fatigued
Clutch spring hooks broken
Air filter dirty
Control valve not opened fully
Leak in fuel hose from tank to
carburetor
Setting of high speed screw (H) too
rich
Tank vent faulty
Fuel pickup body dirty
Fuel strainer dirty
Main jet bores or ports blocked
Pump diaphragm damaged or
fatigued
Ignition timing wrong, flywheel out
of adjustment
– key in flywheel has sheared off
Remedy
Readjust idle speed screw
LA (counterclockwise)
Replace the clutch spring or install
new clutch
Replace the clutch spring
Clean or replace fleece filter;
replace paper filter
Check the throttle cable and re-
adjust if necessary.
Seal connections or install new fuel
hose
Check basic carburetor setting,
correct if necessary
Fit new tank vent
Fit new pickup body
Clean fuel strainer in carburetor,
replace if necessary
Clean the carburetor
Fit new pump diaphragm
Install new flywheel
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