A useful device that all amateur engine-tuners should contemplate purchasing is the Color-Tune 2 kit. Using this device will eliminate a lot of guesswork when adjusting your carburetter to obtain the correct air-fuel ratio.
The Color Tune is a sparking plug with a heat resistant borosilicate glass top, and after removing a sparking plug, you replace it with the Color Tune plug. This enables you to watch the changing colour whilst adjusting the mixture control of the carburation.
We tried the Color Tune to find the correct mixture adjustment on the twin S.U. carburetter of an M.G. Midget. Following the instructions, clearly laid out in the handbook, we found some difficulty in attaching the plug lead to the Color Tune plug as the adaptor provided seemed to be the wrong shape. We finally fitted it and started the engine, to find that the colour viewed through the glass top showed light blue, which according to the colour chart in the book indicated a weak mixture. Adjustment to the mixture control deepened the colour to a darker shade, which the instruction book told us was the “spot-on” mixture. After attaining the identical colour with the other carburetter, we took the M.G. Midget on the road to find an improved performance of engines and all types of carburetters, even fuel injection, and we found the device easy to use.
Obtainable from Colortune, 66 Royal Mint Street, London, E.1, or through the usual trade channels.—I. R. T.