微小的MCE粘贴大图像问题

I'm using the paste plugin on tiny-mce and the submit buttom send me the data of the images correctly on base64. The story so far is perfect. The problem becames when I trying to send a "big" image (it doesn't work with 700KB or upper images size), that the POST I recive on PHP is almost empty, it's like that:

content

<p><img alt="" /></p>

When I usually have

<p><img alt="" src="(all the base64 code)"/></p>

I think the problem is not about the size of the POST (I even sent 18 images together with no problem) but it should be a tinymce configuration issue. Why is that?? Does it happen to someone else?