Stihl TS 420 Manual page 16

Problem
Engine will not idle, idle speed too
high
Engine stops when idling
TS 410, TS 420
Cause
Throttle shutter opened too wide by
idle speed screw LA
Oil seals / crankcase leaking
Air valve soiled
– air valve does not close
Air valve moves stiffly
Throttle rod moves stiffly
– throttle shutter does not close
Idle jet bores or ports blocked
Low speed adjusting screw "too
rich" or "too lean"
Setting of idle speed screw
incorrect – throttle shutter
completely closed
Remedy
Set idle speed screw LA correctly
Seal oil seals / crankcase, replace if
necessary
Clean air valve, replace if
necessary
Check air valve, replace if
necessary
Restore easy movement of throttle
rod
Clean the carburetor
Correct setting of low speed
adjusting screw L
Correct setting of idle speed
screw LA
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