If your menu is anything like http://demos.kendoui.com/web/menu/orientation.html with horizontal orientation, then you need to change:
.k-menu .k-item>.k-link>.k-i-arrow-e {
right:0px;
}
It's absolutely positioned so you need to play with top/left/bottom/right to get it where you want to, and also why the margins don't seem to have effect