10 FC 75, FC 85, FH 75, FS 75, FS 80, FS 85, HL 75, KM 85, KW 85
4.3 Fuel System
Condition Cause Remedy
Engine stalls at idle speed dle jet bores or ports blocked Clean jet bores and ports and blow
clear with compressed air
Idle jet too rich or too lean Reset low speed screw (L)
correctly
Setting of idle speed screw
incorrect – throttle shutter
completely closed
Reset idle speed screw (LA)
correctly
Engine speed drops quickly under
load – low power
Air filter plugged Clean the air filter or replace if
necessary
Tank vent faulty Clean the tank vent of replace if
necessary
Leak in fuel line between tank and
fuel pump
Seal or renew connections and fuel
line
Pump diaphragm damaged or
fatigued
Fit new pump diaphragm
Main jet bores or ports blocked Clean the bores and ports
Fuel pickup body dirty Install new pickup body
Fuel strainer dirty Fit new fuel strainer
Setting of high speed screw (H) too
rich
Reset high speed screw (H)
correctly
Throttle shutter not opened fully Check linkage
Engine will not idle –
idle speed too high
Throttle shutter opened too wide by
idle speed screw
Reset idle speed screw LA
correctly
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