Tech-TorqueYour technical guide to using Gunson tools
Colortune is a unique mixture setting device and a detector of other mixture related problems. It is a spark plug, which runs the engine like any normal spark plug, but because it has a glass insulator, it allows the colour of the combustion flame inside the cylinder to show through andindicate the strength of the mixture.
How Colortune works:
Combustion at its most efficient produces a clear blue flame, various colours result in inefficient mixtures. Inside an internal combustion engine those same colours are present though not normally seen. With Colortune fitted in place of a spark plug, the flame is visible through the glass insulator and the fuel is ignited by the spark in the Colortune.
Now start the engine — the combustion flames will be clearly visible.
On systems which have a slow running mixture adjustment,
The rubber bush in a spark plug spanner will not retain the Colortune as the ceramic is much smaller. A black hex adaptor is
Simple engine tests with Colortune:
Part throttle: If the throttle is opened very slowly the blue flame should become slightly lighter — this is due to a slightly leaner mixture designed to give improved economy at part throttle operation.
Full throttle: When there is a sudden demand for power a richer mixture will prevent a “flat spot”. The blue flame will change to yellow when the throttle is opened.
*Full and detailed instructions are provided with every Colortune kit.
COMBUSTION FLAME APPEARANCE:
The general appearance of the combustion flame when viewed through Colortune is as follows:
Yellow: Indicates a fuel/air mixture which has excessive petrol content(too rich).
Bunsen Blue: Correctly proportioned mixture.
Whitish Blue: Less petrol content(too lean) - at idle, misfiring and engine instability may occur before this lean mixture is fully visible.