The picture does not show the right hand end of the spring.
My first question is aimed at finding out whether you have a problem with a misassembled governor, or you have damaged the speed control cable so it is not moving the speed control bell-crank on the governor. I've attached the B&S manual's diagram of a typical air vane governor. I don't know if the Quattro has an air vane on the flywheel as shown, or a centrifugal governor inside the crankcase, but the principle is the same. In the bottom center of the diagram you can see the speed control bell crank. The speed control cable attaches to that bell crank, just outside the picture at the bottom, and it moves the bell crank. Find whatever your engine uses as a speed control bell crank - in other words, the movable lever at the engine end of the speed control cable that runs from the handlebar control. Does that bell crank move back and forth smoothly when you adjust the speed control on the handlebar? If it does not, you have a kinked or otherwise messed-up control cable, and you need to fix it. If the speed control bell crank moves back and forth as it should, you have a governor malfunction, which you need to fix. Tell us which you have, and we can get into the detail of fixing it.
