We develop our main jets to correctly serve two functions static load and dynamic load. Correct balancing of the carburetors also ensures a smooth idle. On some models the pilot air jet is changed to provide optimum fuel economy. Idle and off idle is controlled by the mixture screws and the float level which have the most positive effect below 4000 R.P.M. Doing so is proof that you are not using the other circuits correctly. Dynojet has found that the engine will idle with the standard pilot jet, with or without the air-box and with the slides and needles removed from the carburetors therefore we never change the pilot jet. This controls 100% of the engine idle and 25% of the transition onto the needle. Dynojet alters this only to achieve the flattest possible fuel delivery curve. The smaller the main air jet, the more fuel you get and less air. The larger the size of the main air jet, the more air you get and less fuel. It controls the amount of fuel which can be pulled from the float bowl into the venturi. This jet allows air into the emulsion tube to mix with fuel being drawn up from the float bowl. This isolates all circuits from each other and ensures easy set-up of the midrange and driveability. then with the correct end dimensions, the needle will have little effect on the main jet regardless of needle position. The needle is designed to give the correct amount of fuel throughout the mid-range and is also designed to allow adjustment from groove 1 to groove 6 with little or no effect below 3000 R.P.M. The design of the needle is where Dynojet spends most of its R&D time. They also have an effect similar to fuel injection by breaking up the fuel as it enters the air stream. In order to achieve full function and driveability, Dynojet develops shrouds or cap style nozzles for adjusting the upper or lower top end. You find the need to lean out for low speed and richen up for top end or leaner on the top end and richer at the low speed. When aftermarket pipes are used, the power curve is usually not flat. Many newer bikes have very flat power and fuel delivery curves when used with the stock exhaust and air-box.
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