var scrollSpeed = 70;
var step = 1;
var current = 0;
var imageWidth = 1000;
var headerWidth = 100;

var restartPosition = -(imageWidth - headerWidth);

function scrollBg(){
    
    current -= step;
    
    if (current == restartPosition){
        current = 0;
    }
    
    $('#clouds').css("background-position",current+"px 0");
    
    
}

var init = setInterval("scrollBg()", scrollSpeed);