Stihl MS 650 Manual page 16

Condition
Engine will not idle,
idle speed too high
Engine stalls at idle speed
MS 650, MS 660
Cause
Throttle shutter opened too wide by
idle speed screw (LA)
Throttle rod sticking
Oil seals/crankcase leaking
Idle jet too rich or too lean
Setting of idle speed incorrect –
throttle shutter completely closed
Small plastic plate in valve jet
does not close
Idle jet bores or ports blocked
Remedy
Set idle speed screw (LA) correctly
Check and free off throttle rod
Seal or replace oil seals/
crankcase
Set low speed screw (L)
correctly
Set idle speed screw (LA)
correctly
Clean or renew valve jet
Clean the carburetor
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