Specular is not 0 by default. If you’d read that link you would know that; the specular input is not used by the engine for metallic materials either, and your mesh is mostly metal. If you want it all on one shader you’ll have to do a little more work than just plugging texture samples into stuff. You can use the aforementioned Lerp node to adjust values for metallic and roughness on the different parts of the mesh.