Ninety % of the engines I have come across and observed do not have the proper low needle valve setting as set at factory. As one major example the Magnum 52 XLS low speed needle comes from the factory at about 2 1/2 turns open. The final setting on these engines turns out to be between 3/8 and 3/4 turn open on the low needle. Please don't take any setting that someone else has set as being correct. You will have to learn how to set up a carburetor for each and every engine you come across. They are all different. If you will Email me direct I will lead you to an excelent write up on tuning engines. [email protected]