I have a Stihl FS70R. I did not use it for a few years and it was running rough. I cleaned the carb, air filter and new spark plug. I adjusted the idle speed and it runs good. I noticed it is using fuel excessively and looks like the exhaust is oily. I use pre mixed 50:1 so that’s not the issue. The carb has three adjustment screws. High, low and idle speed. I can only find adjustments for either high and low or just idle speed. Not all three. What is the adjustment procedure with the three screws? Thank you!