Stihl 064 Service Manual page 15

STIHL 064, 066
Condition
Engine stalls at
idle speed
Engine speed drops
quickly under load
- low power
Cause
Idle jet bores or
channels blocked
Idle jet "too rich"
Setting of idle speed adjusting
screw incorrect - throttle shutter
completely closed
Small plastic plate in
valve jet does not close
Air filter plugged
Tank vent faulty
Leak in fuel line between
tank and fuel pump
Pump diaphragm damaged
or fatigued
Main jet bores or
channels blocked
Fuel pickup body dirty
Fuel strainers dirty
Remedy
Clean jet bores and blow out
with compressed air
Screw in low speed adjusting
screw slightly
(see carburetor adjustment)
Set idle speed adjusting screw
correctly
Clean or renew valve jet
Clean air filter
Clean tank vent or replace if
necessary
Seal or renew connections and
fuel line
Fit new pump diaphragm
Clean bores and channels
Clean pickup body, fit new
filter
Clean fuel strainers
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