Gunson G4074 Colortune Single Plug Kit 14mm

Product Information

The nipples are universal, they are NOT a different size between "car" and "bike" plugs - because cars and bikes often use the same model of plug. A rich and easily ignitable mixture is also provided for starting a cold engine. If a manual cold start device (choke) is fitted, a yellow flame should be visible in Colortune when this is operated. Failing that, could I use a bit of, say copper brake tubing filled with solder as a link between the adaptor and a standard car male-thread nipple, shown in the picture above? That principle is commonly seen in action on paraffin heaters, gas cookers, or anywhere where a fuel is burnt in air to produce heat or energy.

This applies with a hot or cold engine. If enrichment is by electronic control unit (ECU) or auto-choke, test for a yellow flame when the engine is cool / cold. The carbon in the fuel burns with oxygen in the air to produce carbon monoxide (CO), which then burns with more oxygen to produce carbon dioxide (CO2) Just buy the cheapest, most bog-standard type of spark plug you can find and take the nipple off it. When there are no faults present the performance is generally very good under all operating conditions, but even minor faults may have an exaggerated effect. Colortune can provide a unique view of the behaviour of the fuel injection system, in the individual cylinders, which no other equipment can do, saving in many cases time, expense and a great deal of effort in fault diagnosis.

Older versions

There are sometimes exceptions to the above as petrol engines are imperfect machines, these will be described later. We hope you enjoy the excellent technical knowledge, event information and discussions that the BMWMOA forum provides. I have used one for years ( a normal, single kit), its just a case of working your way along the carbs and tweaking the settings, or rejetting as required. Its easier if the carbs are balanced first, but you will have to balance them again afterwards. It takes a while doing a 4, but its do-able. When maximum power is demanded (at full throttle position) it is normal to again have a slightly richer mixture, at most engine speeds there will be a yellow flame.

The development of sophisticated electronic control systems plus a robust exhaust oxygen sensor allowed the three way exhaust catalyst to be introduced.Electric generators with speed governors do not experience rapid acceleration so should have a blue flame under all operating conditions. Determination of the quantity of air going into the engine is itself a difficult task under conditions of varying temperature, varying pressure, and with extreme disruption to the flow caused by valves opening and closing at an incredible rate.

Some exceptions to all the above conditions may be found, for example small engines used in lawn mowers or chain saws may have simple fuel systems which are less able to provide the ideal fuel / air mixture. Colortune features a viewing window so the air/fuel ratio can be adjusted according to flame colour. Ideal for simple and effective engine tuning. With this type of injection system there is little or no facility for adjustment, (except perhaps fuel pump pressure, selection of different settings for different octane fuels etc).

A three dimensional map of the requirements, for a specific engine, is drawn and it is then the job of the injection control system to satisfy this requirement. It is therefore an excellent detector of small percentages of oxygen and the electronic control unit (ECU) is able to continually adjust above and below the point at which the sensor has an output. The ability of the ECU to learn and adjust the programmed map of information stored in its memory, adds a further precision of control.

The fuel needle is machined with a very accurate taper, individually selected for each engine design. Spring loaded types of needle are more accurate when new but they rub against the jet giving errors when worn (e.g. over 50,000 miles 80,000 Km). Appearance of the combustion flame will be rich at the operating conditions where the needle is worn (usually idle / part throttle). If the mixture has been adjusted to normal at idle, weak mixtures will then occur under acceleration. The slide is attached to a needle running in a jet in a similar way to the variable choke carburettor but this does not give a constant depression as the slide position is governed by the throttle position selected at the time, not by a diaphragm. Slide type carburettor. The slide carburettor has been used on motorcycles and other small engines for very many years. Fuel feed is from a chamber with float and needle valve and an idle fuel system is provided with an adjustable mixture screw.There are no progression holes in the idle system as the throttle plate is replaced by the slide which gives this carburettor its name. A high speed fuel feed and adjustment (main jet and main mixture screw) normally located closer to the inlet air cleaner mounting flange.The main fuel discharge feeds into a venturi shape, whose restriction (a fixed size choke) gives a low pressure to pull the fuel in.

Super detailed explanations in the video course

The lighter blue is due to a slightly leaner mixture (less fuel) arranged to give improved economy at part throttle operation. Using the product could hardly be easier, fit it into a warm engine, in place of a spark plug, and you are ready to begin.