Gunson COLORTUNE G4074 Mode D'emploi page 36

ABOVE IDLE SPEED
Symptoms
Yellow Flame at
1000-1700rpm
Yellow Flame
1200 and above
Intermittent yellow
Flame1200 - 1500rpm
Yellow appears at high rpm
only
Light blue flame
engine unstable 1000-2000
rpm
RAPID THROTTLE OPENING
No yellow flame visible at
any speed or flat spot in
acceleration followed by
little yellow flame
Fault details for different fuel systems
Fixed Choke or carburettor with separate idle circuit - restricted
idle air bleed
Variable choke - Worn metering needle/jet
Variable choke - Hole in diaphragm.
Manifold air leak results in a rich setting to compensate for a weak
idle (rich setting then affects whole operating range)
All carburettors - Float chamber level high
Fixed Choke - Main circuit feeding early, Float chamber level too
high. (Lower by 2mm approx) The fuel drips (not spray) if it feeds
too early Variable Choke - Sticky air valve / carburettor piston.
Fixed Choke - Main circuit feeding early, Float chamber level too
high. (Lower by 2mm approx) The fuel drips (not spray) if it feeds
too early Variable Choke - Sticky air valve / carburettor piston.
Blocked main jet or water in the fuel system.
Fixed choke - Accelerator pump not working.
Observe for fuel discharge into choke when throttle is opened
(engine stopped).
Variable choke - Oil damper needs top up
Fuel Injection - MAP sensor or Throttle Position Sensor fault.
Faulty idle switch
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