16
MS 171, MS 181, MS 211
Condition
Cause
Remedy
Engine speed drops quickly under
load – low power
Air filter dirty
Clean the air filter
Throttle shutter not opened fully
Check throttle rod
Tank vent faulty
Replace tank vent
Fuel pickup body dirty
Install new pickup body
Fuel strainer dirty
Clean fuel strainer in carburetor,
replace if necessary
Leak in fuel line between tank and
fuel pump
Install new fuel line
Setting of high speed screw (
H
) too
rich
Check basic carburetor setting,
correct if necessary
Main jet bores or ports blocked
Clean the carburetor
Pump diaphragm damaged or
fatigued
Fit new pump diaphragm
Engine running extremely rich, no
power and very low maximum
speed
Air valve does not open
Check lever on air valve and
replace if necessary
Engine running too rich, low power
and low maximum speed
Air valve does not open fully in full
throttle position
Check lever on air valve and
replace if necessary
Erratic idle – too lean
Air valve does not close properly
Check lever on air valve and
replace if necessary
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