Stihl MS 290 Manual page 13

Condition
Engine will not idle,
idle speed too high
Engine stalls at idle speed
Engine speed drops quickly under
load – low power
12
Cause
Throttle shutter opened too wide by
idle speed screw (LA)
Engine leaking
Idle jet bores or ports blocked
Idle jet too rich or too lean
Setting of idle speed (LA)
incorrect – throttle shutter
completely closed
Small plastic plate in valve jet
does not close
Air filter dirty
Throttle shutter not opened fully
Tank vent faulty
Fuel pickup body dirty
Fuel strainers dirty
Leak in fuel line between tank and
fuel pump
Setting of high speed screw (H)
too rich
Main jet bores or ports blocked
Pump diaphragm damaged or
fatigued
Remedy
Reset idle speed screw (LA)
correctly
Seal the engine
Clean jet bores and ports and blow
clear with compressed air
Set low speed screw (L)
correctly
Set idle speed screw (LA)
correctly
Clean or renew valve jet
Clean the air filter
Check linkage
Clean tank vent or replace if
necessary
Clean the pickup body, fit a new
filter
Replace the fuel strainers
Seal connections or install a new
fuel line
Rotate high speed screw (H)
clockwise (leaner), no further than
stop
Clean the carburetor
Fit new pump diaphragm
MS 290, MS 310, MS 390