Hello,
I am not sure if there is a better way or not, but the only way I have found is by using the “Get Player Camera Management” block, in there you will find two variables “View Pitch Min” and “View Pitch Max” if you set these manually prior to reaching the “Add Controller Pitch Input” this will restrict the camera movement between the min and max pitch.
Call it a manual clamp 
to find the correct segments you will need to have “context match” unchecked.
the other way is to create a class from scratch and manually code the restriction in, for me the BP is the easiest way and it actually works!
Bear in mind I use Unreal Engine 4.10 (not sure if it is in the older versions or not)
How ever the principle is the same as for the YAW, see second screenshot.
I hope this helps
Screenshot below:
