What both gentlemen said is right on and another good thing to know is that after you get the engine started, very small adjustments on that low speed needle are recommended. One eighth of a turn is a bunch. If this needle is set just below the plastic and the engine starts, it will be rich. A very small adjustment on the low speed needle is required and then let the engine run a few seconds to see where the engine is going to settle in. The effects of any adjustment on the low speed needle are not immediate. Let the engine run a few seconds after adjustment to see where it ends up. You might actually want to run the engine up to full throttle for a few seconds after adjusting the low speed needle to clear out any over rich mixture and then let it settle back to idle.