DON'T mess with low speed needle for initial break-in. They come from the factory pretty much right on. For the first few tanks of fuel run the high speed at about 5 turns out for a saito 91 or larger, as for 91 or less keep it at the 2.5 turns out. Also keep in mind not to exceed the 4000rpm mark while on the first few tanks of fuel. These are not 2-strokes, and require not only a little more cash to buy, but a little more tlc.