Don't know what Tecumseh carburetor you have but. This is a common problem with the Tecumseh. On the original Tecumseh carburetor you will find one or two expanding plugs depending on what carb. you have. When the carburetor is cleaned the person that is cleaning the carburetor just doesn't remove these expanding plugs. Under these plugs you will find some very small holes in which they need to be cleaned out with some small diameter tag wire. As for your replacement carburetor I have no idea what is wrong. The surge has to do with the low speed circuit of the carburetor being plugged.