Carburettor Tuning Made Easy

Press, Volume CIX, Issue 32127, 24 October 1969, Page 9

Carburettor Tuning Made Easy

Setting carburettors to deliver the correct mixture is usually a major problem for the home mechanic, particularly if his car has twin carburettors. A British device which is said to make accurate carburettor adjusting both quick and simple has recently come on the market in New Zealand, and the unit appears to do all that is claimed for it. The Colortune Two is not cheap at $14.50, but if one considers the cost of tune-ups and the amount of petrol wasted by an over-rich carburettor setting, the price does not seem excessive, althougn it is well above the British price of the instrument

The device can best be described as a transparent spark-plug, although this is an

over-simplification. It comes complete with a very comprehensive book of instructions, a brush and fluid for cleaning the device, and spacers so the unit will fit different engines.

The unit can be used for both two-stroke and fourstroke engines, with all types of carburettor, and with fuel injection. It is screwed into a cylinder in place of a spark plug, and connected to the hightension lead by an adaptor supplied with the kit When the engine is started, the colour of the burning mixture in the cylinder can be seen through the top of the borosilicate glass insulator. COLOURS KNOWN

Mixtures of petrol and air burn at known colours: a rich mixture burns with an orange colour, the correct mixture for variable-jet carburettors (12 of air to one

of petrol) burns with a Bun-sen-blue flame, the correct mixture for fixed-jet carburettors (15 of air to one of petrol) burns with an intense whitish-blue flame, and a weak mixture burns with a “washed-out” white - blue flame. In practice, one adjusts the appropriate carburettor for the cylinder until the orange flame is visible, then leans the mixture until the Bunsenblue or intense blue-white colour appears, whichever is correct for the type of carburettor. The device is surprisingly sensitive, and tuning can be either for economy or power. The tuning must be done with the bonnet of the car in the

garage, for the colour is very hard to see in strong light. When the device was used on a twin-carburettor car which the owner had spent more than an hour road-test-ing and carefully tuning “by ear,” it immediately showed the mixture was too rich, rather more so on one carburettor than the other. The correct adjustment was quickly made, the car ran very much better, and the whole process took little more than 10 minutes from opening the bonnet to closing it again. On another car the unit showed that a carburettor previously set on a servicestation electronic tuning bench was correct, the second carburettor, tuned “by ear,” was too rich. On a car tuned “by ear” by a mechanic, the unit showed the front carburettor consider* ably too rich, the rear carbu* rettor slightly too rich. The drivers of all three cww reported smoother running and better performance after tuning with the unit. The Colortune has been extensively tested overseas, and the excellent reports it has received seem fully justified. It can be used for all types of petrol-driven motorvehicles, marine engines, chain-saws, power mowers, motor-scooters and motorcycles.