1. From 3/4 to full throttle, the additional flow of air is regulated by the position of the slide. As the slide nears the top of the bore, the cutaway has less and less effect. A higher vacuum is then created at the high speed
3/4 to Full Throttle: Slide and High Speed
Main Jet (Fig. 132)
2. As the needle is raised higher in the high speed needle jet, it becomes less effective in metering the flow of fuel accurately. As the slide reaches wide open throttle, the high speed main jet controls the flow of fuel.
3. To vary the mixture from 3/4 to full throttle, it is best to fit a larger high speed main jet to richen the mixture, or a smaller one to make the mixture leaner.
4. NOTE: Each metering system blends gradually with the one preceding it and the one following it. The objective of regulating the carburetor is to arrive at a condition wherein there is a smooth transition from one metering system to the next and the proportion- of fuel and air remains the same from closed throttle to full throttle.