Using Spin causes rotation I am using spin on extruded faces but for some reason it twists as it rotates.

This is what i have before i press spin:



So when i press spin i get this result:



Why does this twisting happen? I am using a mirror modifier don't know if that matters but if so the settings for it are:

Axis X and Z ticked.
Options:
Merge &amp; Vertex ticked.

I was hoping it wouldn't twist but would just do a nice curve so the faces were facing outwards. 

Am i misunderstanding how Spin works with the cursor?
Yes, you are misunderstanding how Spin works. Spin takes your selection and does a spin extrusion about the 3D Cursor, from the current perspective of the 3D Viewport.

Here's a screen shot to illustrate:



If you want your spin extrusion to be in alignment with a specific axis, align your 3D Viewport accordingly and enter Orthographic View before executing the Spin.