Youtube Video Embed Size Not working

The Arcade Basic theme is effecting the the size of the embedded videos. It is overriding youtube’s embedded video sizes and replacing it with its preset one.

The preset one is far to large for laptops which many people use.

Is there a way to let youtubes setting work??

Here is youtubes embed code. As you can see it has width and a height properties that are being overridden.

<iframe width="640" height="360" src="//www.youtube.com/embed/yazr8JkazmE?list=PLrEnWoR732-CJAHitqRdoP_qUVUbgVdrG" frameborder="0" allowfullscreen></iframe>